https://wiki.diyfaq.org.uk/api.php?action=feedcontributions&user=87.112.195.193&feedformat=atomDIYWiki - User contributions [en]2024-03-28T22:51:52ZUser contributionsMediaWiki 1.35.9https://wiki.diyfaq.org.uk/index.php?title=Earthing_and_Bonding&diff=10082Earthing and Bonding2008-09-27T00:25:08Z<p>87.112.195.193: /* Supplementary bonding */ potential - voltage</p>
<hr />
<div><br />
''In a discussion on the uk.d-i-y newsgroup John Rumm gave [http://groups.google.co.uk/group/uk.d-i-y/msg/a0854fb0707b63a7 this explanation] of Earthing and Bonding, which is the basis for this article.''<br />
<br />
----<br />
<br />
'''Earthing''' and '''bonding''' are often confused (sometimes even referred to as "earth bonding"). This article attempts to clarify the subject.<br />
<br />
==Earthing==<br />
<br />
Earthing ensures that in the event of a fault, adequate fault current will flow causing rapid operation of a Circuit Protective Device (fuse, circuit breaker, or RCD) promptly disconnecting the supply. This limits the duration of any shock that one might receive, dramatically reducing the risk of serious injury or death. <br />
<br />
For example, suppose a poorly positioned live wire in a washing machine becomes abraded by a sharp metal edge when the machine is running and this has the effect of making the casework of the machine "live". Since the case is connected (via its 13A plug) to mains earth, a high current will flow which will either blow the fuse in the plug and/or trip the RCD protecting the circuit.<br />
<br />
During fault conditions, earthing may also reduce the voltage rise of anything earthed, which in addition to the limiting of the shock duration described above can also reduce the shock risk. <br />
<br />
On general purpose socket circuits, the size of earthing conductors, and the circuit protective devices used are chosen to ensure that a fault is cleared within 0.4 seconds (or 0.2 seconds if the installation uses [[TT Earthing]]). For submains or higher power circuits feeding fixed equipment the time limit is 5 seconds (or 1 with TT)<br />
<br />
== Bonding ==<br />
<br />
Two types of bonding are recognised: '''Main''' and '''Supplementary'''<br />
<br />
===Main Bonding===<br />
<br />
Main bonding is the electrical interconnection of incoming (metallic) services (e.g. water, gas, and oil pipes) plus any extraneous conductive parts of a building (like the metal framework used in some buildings, or the central heating pipework), to the main electrical earth. This ensures that under fault conditions things like pipework running through a building are not able to take on a dramatically different electrical potential to that of the installation's earth connection. Note this also covers the fault situation where it is the installations electrical earth itself that is introducing the dangerous voltage.<br />
<br />
====Main bonding: typical wire size requirements====<br />
{| border="1" style="text-align:center" cellpadding="3"<br />
<br />
! Earthing system (see [[Earthing Types]]) || Wire CSA (mm²) <br />
|-<br />
| TN-S || 10<br />
|- <br />
| TN-C-S || 10<br />
|- <br />
| TT || 6<br />
|}<br />
<br />
''Note in these values apply where the size of the neutral of the supply is of 35mm² CSA or less, and where the supplier has not specified another size be used''<br />
<br />
Connections to service pipework should be made as close as possible to the point of entry into the building (but on the consumers side of any meters etc), using the correct BS 951 clamps. Main bonding conductors can be run independently to each service, or a single one may be looped through several so long as the conductor is unbroken at each termination point. <br />
<br />
=== Supplementary bonding ===<br />
<br />
''Supplementary'', or ''cross'' bonding is usually found in ''special locations'' containing a bath or shower. Unlike earthing it is not designed to clear a fault. What it does is electrically tie together all accessible conductive parts (pipes, taps, electrical appliances etc) that could under fault conditions introduce a dangerous potential (voltage) into the room. <br />
<br />
For example suppose an electrically heated towel rail develops a fault which makes it electrically live. (Of course this also supposes that it is not earthed properly: which should never happen but the regulations adopt a belt and braces approach). Without bonding, such a fault would result in the towel rail being at mains voltage, while adjacent basin taps might offer a path to earth via the water pipework. This would be a very dangerous situation since touching both towel rail and a tap would expose one to a 230V potential difference across the arms and chest (including heart) probably causing severe injury or death. <br />
<br />
However if the pipework feeding both hot and cold taps is bonded together with that of the earth of any electrical circuits supplying the room, then the towel rail fault will try to bring both taps up to mains voltage (230V). However touching both rail and tap at the same time exposes one to a potential ''difference'' of zero volts. <br />
<br />
(Actually the bonding may fail to tie all elements together at exactly the same potential, but it is designed to limit any potential difference to 50V or less).<br />
<br />
<br />
<br />
'''Notes'''<br />
<br />
# For equipotential zones to work ''all'' accessible conductive parts (such as the earth wires of any circuits feeding power into the room as well as metal plumbing - central heating as well as hot and cold water) must be securely electrically connected together, and there must be no conductive items or surfaces connected independently to earth unless also included in the bonding. (note that in some buildings (e.g. a greenhouse) this can be very difficult to achieve)<br />
# Electrical appliances with exposed metalwork, may be bonded via their earth (or circuit protective) conductors, and do not necessarily need separate bonding wires or earth clamps. In the example above, the equipotential bonding is between the flex outlet supplying the towel rail and the piework, and there is a disconnection in the earth core of the flex to the towel rail, then the metalwork of the towel rail won't be equipotentially bonded to the piework and a dangerous potential difference (voltage) can arise.<br />
# It is the conductive pipework (etc) ''entering'' the special location which must be bonded: if there is a mixture of metal and plastic pipework, plastic plumbing connectors etc, then it is the pipework coming into the room, not any downstream of plastic sections, which must be bonded.<br />
# There is no requirement to explicitly connect supplementary bonding to the main earth terminal in or adjacent to the consumer unit, although in practice there will often be a connection by default via the circuit protective conductors of any circuits that are included in the equipotential bonding.<br />
<br />
====Supplementary bonding: typical wire size requirements====<br />
<br />
Where a mechanically unprotected single wire is used to effect the bonding (e.g. between BS 951 clamps) the minimum CSA is 4mm²<br />
<br />
===Plastic Pipework Installations===<br />
<br />
Generally with plastic pipe installations, supplementary bonding of the pipes is not required. Note however it may still be required between the earths of, say, lighting and power circuits if they are both accessible in the room.<br />
<br />
However if a bathroom is plumbed in a mixture of plastics pipe joined to exposed copper or steel pipework, the metal pipework ''does'' have to be bonded if it runs between the bathroom and some other part of the building, since a fault outside the bathroom could result in the metal pipework inside becoming live.<br />
<br />
=== Installations not in "Special Locations"===<br />
<br />
In rooms which are not "special locations" (i.e. places likely to put you at increased danger from electric shock, typically because you might be wet), there is also no requirement. So for example a cloakroom with WC and basin would not require it (although it is commonly seen in such circumstances).<br />
<br />
=== Change to protection for Special Locations in 17th Edition ===<br />
<br />
Under the 17th edition of the IEE Regs (BS7671:2008) it is permitted to have no (supplementary) equipotential bonding in a room containing a bath or shower providing that the main equipotential bonding is in place, and that all the circuits feeding the room have additional protection from a RCD with 30mA (or lower) trip threshold.<br />
<br />
----<br />
== See Also ==<br />
* [[Earthing Types]]<br />
* [[TT Earthing]]<br />
* [[Ufer Earthing]]<br />
* [[Electrical Circuit Faults]]<br />
<br />
[[Category:Electrical]]<br />
[[Category:Safety]]</div>87.112.195.193https://wiki.diyfaq.org.uk/index.php?title=Electrical_Installation&diff=10064Electrical Installation2008-09-26T11:49:33Z<p>87.112.195.193: /* Labelling and identification */</p>
<hr />
<div>This article is all about the non engineering side of electrical installations. Its purpose is to explain some of the techniques that are used to when installing electrical equipment and wiring in typical domestic situations. <br />
<br />
{{Template:Under-construction}}<br />
<br />
==Cabling==<br />
Cables can be run in a large number of places and ways. However some places are better than others, and certain rules need to be followed to comply with the wiring regulations in some cases. In addition to the practical issues of cable routing, one also needs to think about what materials you are placing the cable in/under etc. since these may have effects that you need to take into account in the electrical design. E.g. a cable buried in an insulating material will not be able to lose heat as quickly as normal, and this means that the maximum current it is allowed to carry is reduced. <br />
<br />
===Wall chasing===<br />
Burying a cable in a wall is a traditional way to hide and protect the cable. Modern cables can be buried directly in plaster, or protected with capping before plastering. Before a cable can be buried however, a chase needs to be cut!<br />
<br />
See the [[wall chaser]] article for more detail on the options for cutting cable chases in plaster and masonry. <br />
<br />
Also don't forget the lazy option of using a pull switch rather than a wall mounted one, or a wireless room thermostat/door bell/network connection/etc in place of a wired one.<br />
<br />
====Getting past coving and skirtings====<br />
It is all well and good chasing a wall with your trusty SDS drill or wall chaser, but what happens when you reach some architectural feature that you don't want to go hacking through, like a deep skirting board or ornate plaster cornice or moulding?<br />
<br />
* Long drill bit: A very long drill bit (we are talking a minimum of 400mm here to get behind small items like picture or dado rails, or more realistically a stonking great 1m long bit bit for skirtings and coving!) can be a handy way to continue a chase behind the feature you are trying to avoid. Ideally one would need to drill straight up or down through the plaster to achieve this. This is usually impossible since you can't get the drill in the right place, or at the right angle since the wall is in the way. With small obstructions (dado etc) this may not matter, drilling down behind it at a slight angle will still be ok. For a longer vertical chase, the longer bit will be required. The trick here is to apply some sideways force to the bit as you drill. It should be possible to bend the drill such that its tip *is* parallel to the wall, while keeping the drill body and you hands at the slight angle required due to the obstruction of the wall. <br />
<br />
* Cranked gouging chisel: specially made SDS gouges can also work well for getting behind smaller items. <br />
<br />
* Using the other side of the wall: As simple as it sounds, in some cases the solution to avoiding difficult chases, might be to simply use the other side of the wall. This can be ideal for a cable chase on a tiled wall in a bathroom. It can also often save time where adjacent rooms have light switches "back to back" on the dividing wall - only one chase is required for the pair. Note One will need to take care that cable routes are within the prescribed zones expected - even if this means installing an extra accessory to mark the position.<br />
<br />
* A long threaded bar and a lump hammer. A long SDS bit may still damage very deep coving as it is not always possible to get the drill into a vertical position. A slightly bent threaded bar can be knocked up behind deep coving and not damage it<br />
<br />
===Under floors===<br />
Cables are also often taken under suspended floors or even sometimes placed into chases cut into concrete ones. <br />
<br />
====Lifting floors====<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|+ '''Techniques for lifting floors<br>'''<br />
|-<br />
!Type of floor<br />
!Methods<br />
|-<br />
| Traditional floorboards <br />
| A traditional boarded floor is one of the easier ones to get under! The traditional approach simply uses a pry bar and or bolster chisels to leaver it up. Sometimes you also need to cut a board. There are a number of approaches to this:<br />
<br />
* floorboard saw (one with a curved toothed section) will allow a plunge cut to be made over a joist.<br />
* Japanese style [http://www.axminster.co.uk/product-Ice-Bear-Japanese-Azebiki-Panel-Saw-20285.htm azebeki saws] are even better.<br />
* Bend 'n' saw - sometimes if the boards have enough bend in them, you can leaver one up in the middle of a section, and slide a chisel under it propped up on the adjacent boards. This will then let you at it with a traditional panel or tenon saw. <br />
* If you know the thickness of the boards, then you can snap off a jigsaw blade such that when the jigsaw is at the lowest part of its stroke, the blade is the same depth (or fractionally deeper) than the boards. If needs be a hold can be drilled to allow the blade some entry room.<br />
* If you are in a hurry, a [http://www.diyfaq.org.uk/powertools/circularsaw.htm plunge cut] with a circular saw - again with the depth set to no deeper than the board depth. <br />
* Oscillating multi-tools like the Fien Multimaster and the similar concept Bosch PMF 180, really come into their own here since they allow perfect neat plunge cuts into boards. The very narrow kerf of the blade also leaves far less visible damage once the floor is put back down again. <br />
<br />
|-<br />
| Tongue and groove floor boards || Similar to the above, except you will also have to rip cut through (or split off) the tongue on the board first, in order to be able to lift it. <br />
<br />
|-<br />
| Chipboard sheet <br />
| Generally far harder to work with since the boards are not only tongue and grooved at the edges, they are also large (typically 8' x 2'). In many modern houses, its also not uncommon for the partition walls to be built over the floor panels or at least the skirtings etc to be fixed over them. This can make removal of a whole board impossible. The best way to deal this this floor is to cut an access panel:<br />
<br />
* The Trend [http://www.axminster.co.uk/product-Trend-Routabout-Jig-23103.htm Routabout jig] is designed for this purpose, and makes it easy to not only get access, but also fix the hole afterwards. <br />
* The jigsaw, oscillating tool, and circular saw options described above also work. You will need to use screws and battens under the cut edges however to restore the strength of the floor afterwards (chipboard is string in gig sheets, but small strips are quite weak without support on all sides).<br />
<br />
|-<br />
| Laminate <br />
| While not easy it is possible to remove a plank of laminate in a floor. For the click together type, it may be simplest to start un-clicking panels at the edge of the room, and work your way back to where you need your access point. For glued panels, you will need to cut out a board. The way to do this is with a circular saw (preferably a small one - cordless ones are ideal). Set the cut depth to laminate thickness, and cut through the board all round close to its perimeter. Once the main bit is removed, use a chisel to break away the remaining edges from the adjacent boards.<br />
<br />
To replace the board you will need to cut away the underside section of the groove edges of the new plank, and then glue and lower the new board into place. Depending on how cleanly you were able to remove the tongue from the groove of the adjacent board, you may also need to cut this off the new board. <br />
<br />
|-<br />
| Concrete <br />
| Concrete floor screeds can be chased, but care should be taken. Many 'suspended' or 'block and beam' concrete floors are made from interlocking prefabricated components and are fully structural, and should not be chased without consulting the manufacturers or a structural engineer. When installing conduit in floors, consideration should be given to the possibility of condensation in the conduit draining to the lowest levels.<br />
<br />
|}<br />
<br />
====Entry via a ceiling====<br />
The lateral thinkers way to get under a "difficult" upstairs floor is via the ceiling of the room below. In many cases some new plasterboard and a bit of patching is a much quicker solution that lifting an engineered wood floor and underlay, or clearing a particularly cluttered room. <br />
<br />
====Joists====<br />
Most floors are held up by these. When they are running the direction you want your wire to go, all is well with the world and you have a nice easy job (mostly!) However, when you want to get across them, then life is more difficult! Many of the techniques listed elsewhere in this article for dealing with hollow walls can be applied to joists as well. However given they are holding your floors and ceilings up, you want to be a little careful how you go hacking them about. <br />
<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|+ '''Getting across joists<br>'''<br />
|-<br />
!Technique<br />
!Notes<br />
|-<br />
| Drilling <br />
| You can drill through the side of a joist. However you should only drill in the middle of the side, and not at the top or bottom, since the middle section has least stress on it. You should also not drill near to the ends of a joist, since this increases the possibility that the end of the joist could fail in "shear" (i.e. split along the length at the end, making the whole lot weaker). Another advantage of drilling the centre of the joist, is that your cables should be well away from any nails or screws. <br />
<br />
To meet current building regulations, the hole does not want to be more than 0.25 times the total joist height - so a 2" hole on a 8" joist is about the limit. It should also not go closer to the end of the joist than 1/4 of the span (so no nearer than 1m from the end of a 4m joist), and no closer to the centre than 0.4 times the span.<br />
<br />
Take care not to over stuff the holes, since you don't want to reduce the current carrying capacity of your cables by bunching lots of circuits together. <br />
<br />
If you need another hole, leave gap equal to at least three diameters between one and the next. <br />
<br />
The posh way to get between joists is with an angle drill:<br />
<br />
[[Image:AngleDrillLength.jpg]]<br />
<br />
Fitted with a short auger or a spade bit with part of the shaft cut down, these will get between most joists. However you may find a small cordless drill or an impact driver will also fit. If you can't get a drill in, then a long drill bit at an angle can be a last resort.<br />
<br />
|-<br />
| Notching<br />
| Notching is the process of hacking a lump out of the top of the joist (tenon saw and chisel, or oscillating saw being the easiest options here). Unlike drilling, this is better done at the ends of the joist and not near the middle of the span, since it weakens it in bending but not as much in shear. <br />
<br />
A notch should be no deeper than 1/8th of the joist depth (so 1" on a 8" deep joist is the limit).<br />
<br />
Notches must go between 0.07 and 0.25 times the span. So with a 4m joist that would be anywhere between 280mm and 1m from either end.<br />
<br />
Additional care must be taken to protect the cables from nails and screws. You can buy metal plates to place over the top of notches to achieve this. <br />
<br />
|}<br />
<br />
===Over Ceilings===<br />
In some cases the same as under a floor! However this also includes over false ceilings (which if you have lots of wires to hide or lots of ceiling piercing lights to install, may be well worth building for the purpose). It also includes through loft spaces. Once caution to watch is to keep modern PVC cable away from polystyrene insulation (the plasticiser leaches out of the PVC into the polystyrene, leaving a gooey mess, and rather brittle cable insulation)<br />
<br />
<br />
===In hollow walls===<br />
It is also sometimes possible to drop a wire down a hollow stud wall (either plasterboard or lath and plaster). Note it is not recommended to place wires in the cavity of exterior walls, where they could cause dampness bridging, and be adversely affected by cavity wall insulation injected at a later stage. <br />
<br />
Getting wires into a stud wall in the first place is easy to do when building it. However at a later date it is not as easy and you may meet a few obstacles:<br />
<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|+ '''Getting round problem walls<br>'''<br />
|-<br />
!Problem<br />
!Solutions<br />
|-<br />
<br />
<br />
|-<br />
| Catching a wire<br />
| Feeding a wire along the inside of a wall is one thing, but getting the free end out again without making a hand sized hole in the wall is another problem! Techniques to try include:<br />
<br />
* Standard retractable tape measure. Push a loop of this into the wall through a hole. If you keep feeding in tape, then inside the wall it will expand out against the sides etc. This makes a larger target to feed the wire through. Pulling the loop of tape back through the hole can then "snare" the cable. <br />
* The same trick also works (better) with a length of flexible plastic coated net curtain wire used as the loop.<br />
* A length of chain, can also make a good weight to pull a draw string through. It has the advantage of being easy to "catch" with a magnet or magnetic pick up tool. <br />
<br />
|-<br />
| Getting past studs and noggings<br />
| It is rather hard to drill a hole through the side of a lump of wood if all you can see is a board covering its front face! However there are ways:<br />
<br />
* Long drill bit. If you have a hole to work from (say a cutout for a socket box) then a long drill bit at an shallow angle can be used to get through at least one obstruction. Spade bits with an extension shaft or two can be very useful here since they let you make a big diameter hole at some distance. <br />
* Notching from the face. You can cut a notch in the face of a stud or nogging without causing too much damage to the face of the wall, by drilling a series of overlapping holes with a wide spade or auger bit. <br />
<br />
<br />
|}<br />
<br />
===Pull wires / cords / tapes===<br />
Ideal for getting wires through tortuous paths. There are specialist tapes and cords for the purpose, but almost any bit of string or even and old cable may be used. Fishing line is often very good in that it is strong, long, thin, slippery, and cheap! The real art with any pull string is how you get it into location in the first place! Some of the more imaginative options include:<br />
<br />
* Add a weight or ball to the end and throw, catapult, or otherwise propel it in the desired direction. A metal weight like a small bit of chain can make retrieving the end easy with a magnet on a stick. <br />
<br />
* Radio controlled cars and other self propelled toys, can be "driven" to the destination while towing a wire - handy for ground floor voids that are not big enough (or too full of rat crap) to make climbing under yourself desirable. <br />
<br />
* Small children can often be pressed into service with some bribery ;-)<br />
<br />
* Cat, cable tie, and a sardine might also work!<br />
<br />
There is a whole subset of these, for getting a pull cord through ducts and pipes. Most involve either a vacuum cleaner to suck something through the ducts, or a compressor to blow something through it. Rags, plastic bags, and tennis balls being tried and tested candidates. <br />
<br />
Also when pulling pull cords, you may need to allow for the possibility that all you will pull with the first cord is a stronger cord! Working your way up to the particularly heavy or stiff cable that ultimately needs to get through. <br />
<br />
One handy tip when laying in wires in many cases, is to pull a new cord through with each wire. That way you can always add more later. <br />
<br />
===Lubricants===<br />
Sometimes some extra assistance is needed when getting wires and cables through tight spaces and into pipes, ducts, conduits etc. There are specialist cable pulling lubricants available like "Yellow 77" that are designed for this purpose and won't hurt or react with the cable in any way. However other substances are often used:<br />
<br />
* Talc<br />
* Grease (silicone is better - won't attack the plastic)<br />
* PTFE sprays<br />
* WD40 (not much good - but sometimes better than nothing)<br />
* Soap / washing up liquid<br />
<br />
(don't use graphite power - it conducts electricity!)<br />
<br />
===Push rods and sticks===<br />
Very useful for getting wires through awkward spaces. The simplest (and a widely used) stand in for "real" ones, are simply lengths of plastic conduit or trunking (and especially the lid off a bit of mini trunking!). The posher versions look rather like a narrow gauge version of a set of drain rods. Often made from fibreglass, they can be screwed together to make a very long stick (10m is not uncommon) and the end of the stick can be equipped with hooks and loops and other gizmos to make getting them round corners easier. <br />
<br />
One word or warning with the fibreglass sticks, wear gloves when handling them - otherwise you can get a nasty glass splinter!<br />
<br />
==Tools==<br />
The following is a big list of tools, some are essential, and some just handy to have. Essential in this case means these are tools that you need to do the job safely - you may be able to do it will less, but you may be putting yourself at risk when doing so. <br />
<br />
Many of the mechanical aspects of wiring have little to do with the things that one traditionally associates with the work of an electrician, and are really nothing more than general building and carpentry tasks. <br />
<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|-<br />
!Type<br />
!Description<br />
!Need<br />
|-<br />
| SDS Drill (3 function)<br />
<br />
| The ability to not only drill holes, but also quickly and neatly chisel out holes for socket boxes, and neat wall chases make the SDS drill a wonderful time saver. <br />
| Very Handy<br />
<br />
|-<br />
| Cordless drill / driver<br />
| In general cordless tools are very handy to have for electrical work since you will often be working in areas without power. Making holes, and fixing things in place probably come right near the top of list of tasks faced by anyone undertaking electrical work. A medium size (say 14.4V or better) combi drill is ideal for this sort of work. Having the hammer facility can make drilling holes into masonry for wall plugs far simpler. <br />
| Very Handy<br />
<br />
|-<br />
| Insulated screwdrivers (VDE) <br />
[[Image:VDEScrewdrivers.jpg]]<br />
| [http://www.ck-tools.com/Key_Ranges/sensoplus.htm VDE tools][1] are insulated and tested to to a high standard. This ensures that should the metal part of the tool make contact with live metalwork, no harm will come to the person holding the other end. These are absolutely essential when working on electrical installations. Not just for the rare occasions where live working is required, but the far more typical cases where one is working in close proximity to live circuits, or even on circuits that really ought to be dead, but are not!<br />
<br />
All things said and done, you can make do some ordinary screwdrivers for jobs not involving work on electrical fittings etc, and you may choose to buy a limited set of VDE insulated drivers: a medium<br />
phillips (typical for MCB terminals) and a small and medium flat blade for<br />
other terminals.<br />
| Essential<br />
|-<br />
|Side Cutters<br />
[[Image:SideCutters.jpg]]<br />
|VDE insulated side cutters are essential (one day, you *will* pick the wrong cable to cut). Side cutters are used for cutting cables and wire to length, and they are also often invaluable for stripping cables of their outer insulation. Some cutters also include specific facilities for wire stripping, [[http://www.ck-tools.com/Key_Ranges/pliers&cutters.htm eg]]. <br />
| Essential<br />
<br />
|-<br />
|Wire Strippers<br />
[[Image:EndStrippers.jpg]]<br />
|Good wire strippers make life very much simpler (while it is true that someone proficient with side cutters can often strip a wire quite satisfactorily with them as well, there is far more scope for bruised knuckles, damaged conductors, and tatty looking wire ends without them). The style of wire cutter is much a matter of personal preference. Side strippers are quick and easy to use - especially one smaller wires. The end action ones may be better for tough insulation found on the thicker and also special purpose wires. Some people also like to have an automatic wire stripper. These can make repeated stripping operations very much quicker. <br />
| Highly desirable<br />
<br />
|-<br />
|Combination pliers<br />
[[Image:CombinationPliers.jpg]]<br />
|regular square nosed medium set are useful for holding, bending, and twisting wires, tightening locknuts etc. In fact anywhere you need extra gripping power. <br />
| Handy<br />
<br />
|-<br />
|Long nose pliers<br />
[[Image:PointedNosePliers.jpg]]<br />
|A good pair of long nose pliers are the ideal tool for fishing wires out of awkward corners, and holding tricky wires in place as you tighten terminal screws. Note however that even with VDE insulated ones, care must be taken, since they have a large expanse of exposed metalwork that could easily short against live parts or earthed casework. <br />
| Very Handy<br />
<br />
|-<br />
|Ratchet action cable crimper<br />
[[Image:CrimpRatchetTool.jpg]]<br />
|Essential for making sound wire joints which will later become inaccessible, or where space is too restrictive to allow terminal (aka "choccie blocks") to be used. See the [[Cable crimping]] article for full details of how to use these. <br />
| Often Essential <br />
<br />
|-<br />
| 20mm Hole Saw<br />
[[Image:HoleSaw20mm.jpg]]<br />
| One of those universal truisms with many electrical accessories is that the "knock outs" are often in the wrong place, or failing that won't actually knock out without wrecking something. A small hole saw is the ideal way to persuade them of the error of their ways!<br />
| Handy<br />
<br />
|- <br />
| Metal, voltage, and stud detector<br />
[[Image:ZirconTriscannerPro.jpg]]<br />
| One of these that actually works (like the one pictured) is a massive time saver. It can find studs behind plasterboard, and buried pipes and cables (and tell you when they are live). Note the stud detection is defeated by foil backed plasterboard, but you can still use the metal detection facility to find the nails or screws that are holding it to the studs!<br />
| Well worth having<br />
<br />
|-<br />
<br />
<br />
<br />
|}<br />
<br />
[1] Just in case you were wondering what VDE stands for, the answer is: It wouldn't<br />
help much as the words are German! It is an internationally accredited German testing <br />
and standards institute. In their own words:<br />
<br />
''"The VDE Testing and Certification Institute is accredited on a national and <br />
''international level for the area of testing and certification of electrotechnical <br />
''equipment, components and systems. Testing of electrotechnical products is <br />
''conducted for safety, electromagnetic compatibility and other characteristics."''<br />
<br />
<br />
==Test gear==<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|-<br />
!Type<br />
!Description<br />
!Need<br />
|-<br />
| Multimeter<br />
[[Image:ClampMeter.jpg]]<br />
| A simple multimeter will be very handy for all sorts of tests, ranging from a simple "Is this wire live?" test, to checking continuity, and measuring cable resistances. <br />
<br />
(The clamp meter shown, also has the capability to measure the current flowing in a single wire (i.e. not a cable containing live and neutral, but either live '''or''' neutral in isolation) without needing to make any electrical connection to a circuit. Clamping this round the meter tails for example will let you read the total current draw on an installation with no risk)<br />
| Essential<br />
<br />
|-<br />
| Test lead extension<br />
[[Image:TestLeadExtender.jpg]]<br />
| Very handy for working out which socket is connected to which and various other tests that require you to measure continuity between more distant points. A workable alternative can be knocked up from any bit of cable or flex, but the proper lead is so much easier to use. <br />
| Handy<br />
<br />
|-<br />
| Volt stick<br />
| A simple non contact indicator that detects the presence of mains voltage on a wire. These are very good testing that a wire is safe to cut etc, when working on partially isolated systems. <br />
<br />
(Note for safety, it is always wise to test the volt stick on a known live circuit both before and after testing the wire you want to know the status of. This protects you from a freak accident should the detector fail at an in opportune moment!)<br />
| Very Handy<br />
<br />
|-<br />
| Socket Tester<br />
[[Image:SocketTester.jpg]]<br />
| A simple plug in tester that will indicate a wide range of potential faults with sockets and their wiring. Very quick and easy to use, and unlike probing about in the back of a socket with your multimeter, or trying to find a suitable appliance to plug into a socket to test it, much safer!<br />
| Very Handy<br />
<br />
|}<br />
<br />
==Advanced test gear==<br />
For anything other than basic alterations and additions to existing circuits, some more sophisticated test equipment is really required. These items can be bought as separate units or as an integrated tester that combines all the functions. Again, you will probably live if you don't use this kit, but it is the only way you are actually going to '''prove''' that your wiring is performing as it should)<br />
<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|-<br />
!Type<br />
!Description<br />
|-<br />
| Insulation resistance tester ("megger")<br />
[[Image:InsulationTester.jpg]]<br />
| These are often multi function devices that measure wire resistances with good accuracy, and are also able to perform resistance measurements using a very high test voltage (e.g. 500V or more). This will detect any part of a circuit (or whole installation) that has failing or damaged insulation. These can be very handy for finding tricky faults causing [http://wiki.diyfaq.org.uk/index.php?title=RCD#Nuisance_trips nuisance tripping] of RCDs for example. <br />
<br />
Great care must be taken with these devices. Firstly they '''will''' give you a shock if you hold the probes and push the test button. Secondly, you need to make sure there is nothing connected to the circuit under test that might be damaged by the high test voltage (some RCDs, Dimmers, and electronic power supplies etc)<br />
<br />
|-<br />
| Earth loop impedance tester<br />
[[Image:LoopTester.jpg]]<br />
| These are very useful devices that will allow you to measure the earth fault loop impedance at any socket in a circuit. This lets you prove the effectiveness of the earth, and establish data you will need for circuit design. They can also be used to measure the performance of earth rods. In many cases they will also let you measure the Prospective Short Circuit current and the Prospective Fault Current of a circuit. <br />
<br />
Older devices like the one pictured, perform tests using a fairly substantial test current. This is good in the sense that it proves that the earth really does work under simulated "fault" conditions, but has the downside of tripping any RCD protecting the circuit under test. More modern devices also have the capability of carrying out non tripping tests. <br />
<br />
|-<br />
| RCD Tester<br />
[[Image:RCDTester.jpg]]<br />
| About the only realistic way to properly test a RCD. These inject a user selectable earth leakage into a circuit, and then time how long (in 1/1000ths of seconds) it takes the RCD to disconnect the power. More sophisticated versions can also carry out "ramp" tests that slowly increase the leakage until the trip point is found. <br />
<br />
Not only required for RCD tests, they can often help establish the cause of nuisance trips.<br />
<br />
|}<br />
<br />
<br />
<br />
==Good workmanship==<br />
Take care of your wires and they will last longer and give less potential problems in the future. <br />
<br />
===Mechanical protection===<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|-<br />
!Type<br />
!Description<br />
|-<br />
| Capping || to protect cables from damage by plastering trowels, capping is ideal (plastic or metal). The advantage of capping over conduit is that it is easy to fit after a cable has been installed, and it won't affect the cable's ability to lose heat. <br />
|-<br />
<br />
| Plastic Conduit || Plastic conduit can be used for added protection to surface run cables. Note it is not well suited to burial since it offers little protection from drills, nails and screws, while lowering the current carrying capacity of the cable. <br />
|-<br />
<br />
| Metal conduit || Metal conduit can be buried, and also (if installed correctly) can be used as the circuit protective conductor (i.e. "earth"). It also offers good protection against penetration. It can also be surface run and offers good protection in harsh service conditions. Metal conduit is not however easy to use, since it requires additional tooling to bend, cut and thread the sections. The installation also needs to be carefully designed, to enable all the cables (or 'singles') in one section of conduit to be drawn through in one pass, and to ensure that cables are not drawn through more than the permitted maximum number of bends or corners (usually equivalent to 2 x 90 degree). Regulations require that all conduit is in place and continuous before drawing in cables. <br />
|-<br />
<br />
| Grommets [[Image:Gromets.jpg]] || Rubber grommets should be used anywhere a cable passes through a hole in a metal enclosure or back box. These will stop the insulation being damaged by sharp edges (not only from movement of the cable during installation, but also from movement caused by vibration or thermal expansion effects in use).<br />
|-<br />
<br />
| Strain relief sleeves || Sleeving can help protect flexes and cables at any point they will be subject to stress caused by carrying their own weight from a suspension point. <br />
|-<br />
<br />
| Glands || When attempting to make a cable entry or exit waterproof, or when working with cables that must be terminated with glands like [[Terminating SWA|SWA]], glands must be used. These not only fix the cable in place but also offer the water protection required, strain relief and often a facility to connect the cable screen (where present) to earth.<br />
|-<br />
<br />
| Minimum bend radii || Care must be taken with cables, to not attempt to bend them too acutely, since this may cause damage. <br />
<br />
|-<br />
<br />
|}<br />
<br />
===Labelling and identification===<br />
A well labelled installation is one of the signs of a good one! Things like:<br />
<br />
* Clear labels on the CU to identify what is protected by each fuse or breaker. <br />
<br />
* Identify main switches<br />
<br />
* Make sure earth and equipotential bonding conductors have the "Safety electrical connection - do not remove" tag on them. <br />
<br />
* Identify main equipotential bonds (gas, water etc)<br />
<br />
* Make sure any wires that are being used in a non obvious way or contrary to the expected use based on their colour, are sleeved with appropriate coloured tape or sleeving. e.g. the switched live returning from a light switch is carried in the black/blue insulated wire, it should be flagged with red/brown at '''both''' ends (you will curse the installer, the next time you remove a ceiling rose, and then notice no marking on the switch wire!)<br />
<br />
* An installation that uses both 'old' (red/black) and 'new' (brown/blue) colour codes must have a warning label affixed to the consumer unit.<br />
<br />
===Support===<br />
<br />
* Clips<br />
* Trunking<br />
<br />
<br />
<br />
==Making good==<br />
Once you have installed and tested all your new wiring, there is the rather more mundane task of filling all the wholes, and reinstating the fabric of the building before you lose too many household pets or children into floor voids or incur the wrath of the style police!<br />
<br />
===Filling chases===<br />
Bonding plaster is cheap and easy. Fill just below the surface to allow a final skim of filler or multifinish plaster. If the wall is old and crumbly, then paint some dilute PVA in the chase first, to stop it sucking all the water out of the plaster. <br />
<br />
Try and avoid getting wet plaster into the back of switches and sockets (or you might find out just how well those RCDs work!)<br />
<br />
If the cables keep popping out of the chase, then the occasion well positioned wide headed clout nail (beside the cable, not through it!), or dab of grab adhesive will keep things in place until the plaster has time to set. Old plaster is ideal for this - it sets faster. <br />
<br />
===Replacing floor boards===<br />
Nail or screw them. If you think they will need to come up again, use screws (they will probably squeak less as well). Where you have had to make cuts that are not over joists, you will need to include additional support. A short length of 2" x 2" screwed to the side of the joist can take the end of a board. <br />
<br />
<br />
==See also==<br />
* [[Rewiring Tips]]<br />
* [[:Category: Electrical]]<br />
* [[Special:Allpages|Wiki Contents]]<br />
* [[Special:Categories|Wiki Subject Categories]]<br />
<br />
<br />
[[Category: Electrical]]<br />
[[Category: Building]]</div>87.112.195.193https://wiki.diyfaq.org.uk/index.php?title=Electrical_Installation&diff=10063Electrical Installation2008-09-26T11:48:04Z<p>87.112.195.193: /* Mechanical protection */</p>
<hr />
<div>This article is all about the non engineering side of electrical installations. Its purpose is to explain some of the techniques that are used to when installing electrical equipment and wiring in typical domestic situations. <br />
<br />
{{Template:Under-construction}}<br />
<br />
==Cabling==<br />
Cables can be run in a large number of places and ways. However some places are better than others, and certain rules need to be followed to comply with the wiring regulations in some cases. In addition to the practical issues of cable routing, one also needs to think about what materials you are placing the cable in/under etc. since these may have effects that you need to take into account in the electrical design. E.g. a cable buried in an insulating material will not be able to lose heat as quickly as normal, and this means that the maximum current it is allowed to carry is reduced. <br />
<br />
===Wall chasing===<br />
Burying a cable in a wall is a traditional way to hide and protect the cable. Modern cables can be buried directly in plaster, or protected with capping before plastering. Before a cable can be buried however, a chase needs to be cut!<br />
<br />
See the [[wall chaser]] article for more detail on the options for cutting cable chases in plaster and masonry. <br />
<br />
Also don't forget the lazy option of using a pull switch rather than a wall mounted one, or a wireless room thermostat/door bell/network connection/etc in place of a wired one.<br />
<br />
====Getting past coving and skirtings====<br />
It is all well and good chasing a wall with your trusty SDS drill or wall chaser, but what happens when you reach some architectural feature that you don't want to go hacking through, like a deep skirting board or ornate plaster cornice or moulding?<br />
<br />
* Long drill bit: A very long drill bit (we are talking a minimum of 400mm here to get behind small items like picture or dado rails, or more realistically a stonking great 1m long bit bit for skirtings and coving!) can be a handy way to continue a chase behind the feature you are trying to avoid. Ideally one would need to drill straight up or down through the plaster to achieve this. This is usually impossible since you can't get the drill in the right place, or at the right angle since the wall is in the way. With small obstructions (dado etc) this may not matter, drilling down behind it at a slight angle will still be ok. For a longer vertical chase, the longer bit will be required. The trick here is to apply some sideways force to the bit as you drill. It should be possible to bend the drill such that its tip *is* parallel to the wall, while keeping the drill body and you hands at the slight angle required due to the obstruction of the wall. <br />
<br />
* Cranked gouging chisel: specially made SDS gouges can also work well for getting behind smaller items. <br />
<br />
* Using the other side of the wall: As simple as it sounds, in some cases the solution to avoiding difficult chases, might be to simply use the other side of the wall. This can be ideal for a cable chase on a tiled wall in a bathroom. It can also often save time where adjacent rooms have light switches "back to back" on the dividing wall - only one chase is required for the pair. Note One will need to take care that cable routes are within the prescribed zones expected - even if this means installing an extra accessory to mark the position.<br />
<br />
* A long threaded bar and a lump hammer. A long SDS bit may still damage very deep coving as it is not always possible to get the drill into a vertical position. A slightly bent threaded bar can be knocked up behind deep coving and not damage it<br />
<br />
===Under floors===<br />
Cables are also often taken under suspended floors or even sometimes placed into chases cut into concrete ones. <br />
<br />
====Lifting floors====<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|+ '''Techniques for lifting floors<br>'''<br />
|-<br />
!Type of floor<br />
!Methods<br />
|-<br />
| Traditional floorboards <br />
| A traditional boarded floor is one of the easier ones to get under! The traditional approach simply uses a pry bar and or bolster chisels to leaver it up. Sometimes you also need to cut a board. There are a number of approaches to this:<br />
<br />
* floorboard saw (one with a curved toothed section) will allow a plunge cut to be made over a joist.<br />
* Japanese style [http://www.axminster.co.uk/product-Ice-Bear-Japanese-Azebiki-Panel-Saw-20285.htm azebeki saws] are even better.<br />
* Bend 'n' saw - sometimes if the boards have enough bend in them, you can leaver one up in the middle of a section, and slide a chisel under it propped up on the adjacent boards. This will then let you at it with a traditional panel or tenon saw. <br />
* If you know the thickness of the boards, then you can snap off a jigsaw blade such that when the jigsaw is at the lowest part of its stroke, the blade is the same depth (or fractionally deeper) than the boards. If needs be a hold can be drilled to allow the blade some entry room.<br />
* If you are in a hurry, a [http://www.diyfaq.org.uk/powertools/circularsaw.htm plunge cut] with a circular saw - again with the depth set to no deeper than the board depth. <br />
* Oscillating multi-tools like the Fien Multimaster and the similar concept Bosch PMF 180, really come into their own here since they allow perfect neat plunge cuts into boards. The very narrow kerf of the blade also leaves far less visible damage once the floor is put back down again. <br />
<br />
|-<br />
| Tongue and groove floor boards || Similar to the above, except you will also have to rip cut through (or split off) the tongue on the board first, in order to be able to lift it. <br />
<br />
|-<br />
| Chipboard sheet <br />
| Generally far harder to work with since the boards are not only tongue and grooved at the edges, they are also large (typically 8' x 2'). In many modern houses, its also not uncommon for the partition walls to be built over the floor panels or at least the skirtings etc to be fixed over them. This can make removal of a whole board impossible. The best way to deal this this floor is to cut an access panel:<br />
<br />
* The Trend [http://www.axminster.co.uk/product-Trend-Routabout-Jig-23103.htm Routabout jig] is designed for this purpose, and makes it easy to not only get access, but also fix the hole afterwards. <br />
* The jigsaw, oscillating tool, and circular saw options described above also work. You will need to use screws and battens under the cut edges however to restore the strength of the floor afterwards (chipboard is string in gig sheets, but small strips are quite weak without support on all sides).<br />
<br />
|-<br />
| Laminate <br />
| While not easy it is possible to remove a plank of laminate in a floor. For the click together type, it may be simplest to start un-clicking panels at the edge of the room, and work your way back to where you need your access point. For glued panels, you will need to cut out a board. The way to do this is with a circular saw (preferably a small one - cordless ones are ideal). Set the cut depth to laminate thickness, and cut through the board all round close to its perimeter. Once the main bit is removed, use a chisel to break away the remaining edges from the adjacent boards.<br />
<br />
To replace the board you will need to cut away the underside section of the groove edges of the new plank, and then glue and lower the new board into place. Depending on how cleanly you were able to remove the tongue from the groove of the adjacent board, you may also need to cut this off the new board. <br />
<br />
|-<br />
| Concrete <br />
| Concrete floor screeds can be chased, but care should be taken. Many 'suspended' or 'block and beam' concrete floors are made from interlocking prefabricated components and are fully structural, and should not be chased without consulting the manufacturers or a structural engineer. When installing conduit in floors, consideration should be given to the possibility of condensation in the conduit draining to the lowest levels.<br />
<br />
|}<br />
<br />
====Entry via a ceiling====<br />
The lateral thinkers way to get under a "difficult" upstairs floor is via the ceiling of the room below. In many cases some new plasterboard and a bit of patching is a much quicker solution that lifting an engineered wood floor and underlay, or clearing a particularly cluttered room. <br />
<br />
====Joists====<br />
Most floors are held up by these. When they are running the direction you want your wire to go, all is well with the world and you have a nice easy job (mostly!) However, when you want to get across them, then life is more difficult! Many of the techniques listed elsewhere in this article for dealing with hollow walls can be applied to joists as well. However given they are holding your floors and ceilings up, you want to be a little careful how you go hacking them about. <br />
<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|+ '''Getting across joists<br>'''<br />
|-<br />
!Technique<br />
!Notes<br />
|-<br />
| Drilling <br />
| You can drill through the side of a joist. However you should only drill in the middle of the side, and not at the top or bottom, since the middle section has least stress on it. You should also not drill near to the ends of a joist, since this increases the possibility that the end of the joist could fail in "shear" (i.e. split along the length at the end, making the whole lot weaker). Another advantage of drilling the centre of the joist, is that your cables should be well away from any nails or screws. <br />
<br />
To meet current building regulations, the hole does not want to be more than 0.25 times the total joist height - so a 2" hole on a 8" joist is about the limit. It should also not go closer to the end of the joist than 1/4 of the span (so no nearer than 1m from the end of a 4m joist), and no closer to the centre than 0.4 times the span.<br />
<br />
Take care not to over stuff the holes, since you don't want to reduce the current carrying capacity of your cables by bunching lots of circuits together. <br />
<br />
If you need another hole, leave gap equal to at least three diameters between one and the next. <br />
<br />
The posh way to get between joists is with an angle drill:<br />
<br />
[[Image:AngleDrillLength.jpg]]<br />
<br />
Fitted with a short auger or a spade bit with part of the shaft cut down, these will get between most joists. However you may find a small cordless drill or an impact driver will also fit. If you can't get a drill in, then a long drill bit at an angle can be a last resort.<br />
<br />
|-<br />
| Notching<br />
| Notching is the process of hacking a lump out of the top of the joist (tenon saw and chisel, or oscillating saw being the easiest options here). Unlike drilling, this is better done at the ends of the joist and not near the middle of the span, since it weakens it in bending but not as much in shear. <br />
<br />
A notch should be no deeper than 1/8th of the joist depth (so 1" on a 8" deep joist is the limit).<br />
<br />
Notches must go between 0.07 and 0.25 times the span. So with a 4m joist that would be anywhere between 280mm and 1m from either end.<br />
<br />
Additional care must be taken to protect the cables from nails and screws. You can buy metal plates to place over the top of notches to achieve this. <br />
<br />
|}<br />
<br />
===Over Ceilings===<br />
In some cases the same as under a floor! However this also includes over false ceilings (which if you have lots of wires to hide or lots of ceiling piercing lights to install, may be well worth building for the purpose). It also includes through loft spaces. Once caution to watch is to keep modern PVC cable away from polystyrene insulation (the plasticiser leaches out of the PVC into the polystyrene, leaving a gooey mess, and rather brittle cable insulation)<br />
<br />
<br />
===In hollow walls===<br />
It is also sometimes possible to drop a wire down a hollow stud wall (either plasterboard or lath and plaster). Note it is not recommended to place wires in the cavity of exterior walls, where they could cause dampness bridging, and be adversely affected by cavity wall insulation injected at a later stage. <br />
<br />
Getting wires into a stud wall in the first place is easy to do when building it. However at a later date it is not as easy and you may meet a few obstacles:<br />
<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|+ '''Getting round problem walls<br>'''<br />
|-<br />
!Problem<br />
!Solutions<br />
|-<br />
<br />
<br />
|-<br />
| Catching a wire<br />
| Feeding a wire along the inside of a wall is one thing, but getting the free end out again without making a hand sized hole in the wall is another problem! Techniques to try include:<br />
<br />
* Standard retractable tape measure. Push a loop of this into the wall through a hole. If you keep feeding in tape, then inside the wall it will expand out against the sides etc. This makes a larger target to feed the wire through. Pulling the loop of tape back through the hole can then "snare" the cable. <br />
* The same trick also works (better) with a length of flexible plastic coated net curtain wire used as the loop.<br />
* A length of chain, can also make a good weight to pull a draw string through. It has the advantage of being easy to "catch" with a magnet or magnetic pick up tool. <br />
<br />
|-<br />
| Getting past studs and noggings<br />
| It is rather hard to drill a hole through the side of a lump of wood if all you can see is a board covering its front face! However there are ways:<br />
<br />
* Long drill bit. If you have a hole to work from (say a cutout for a socket box) then a long drill bit at an shallow angle can be used to get through at least one obstruction. Spade bits with an extension shaft or two can be very useful here since they let you make a big diameter hole at some distance. <br />
* Notching from the face. You can cut a notch in the face of a stud or nogging without causing too much damage to the face of the wall, by drilling a series of overlapping holes with a wide spade or auger bit. <br />
<br />
<br />
|}<br />
<br />
===Pull wires / cords / tapes===<br />
Ideal for getting wires through tortuous paths. There are specialist tapes and cords for the purpose, but almost any bit of string or even and old cable may be used. Fishing line is often very good in that it is strong, long, thin, slippery, and cheap! The real art with any pull string is how you get it into location in the first place! Some of the more imaginative options include:<br />
<br />
* Add a weight or ball to the end and throw, catapult, or otherwise propel it in the desired direction. A metal weight like a small bit of chain can make retrieving the end easy with a magnet on a stick. <br />
<br />
* Radio controlled cars and other self propelled toys, can be "driven" to the destination while towing a wire - handy for ground floor voids that are not big enough (or too full of rat crap) to make climbing under yourself desirable. <br />
<br />
* Small children can often be pressed into service with some bribery ;-)<br />
<br />
* Cat, cable tie, and a sardine might also work!<br />
<br />
There is a whole subset of these, for getting a pull cord through ducts and pipes. Most involve either a vacuum cleaner to suck something through the ducts, or a compressor to blow something through it. Rags, plastic bags, and tennis balls being tried and tested candidates. <br />
<br />
Also when pulling pull cords, you may need to allow for the possibility that all you will pull with the first cord is a stronger cord! Working your way up to the particularly heavy or stiff cable that ultimately needs to get through. <br />
<br />
One handy tip when laying in wires in many cases, is to pull a new cord through with each wire. That way you can always add more later. <br />
<br />
===Lubricants===<br />
Sometimes some extra assistance is needed when getting wires and cables through tight spaces and into pipes, ducts, conduits etc. There are specialist cable pulling lubricants available like "Yellow 77" that are designed for this purpose and won't hurt or react with the cable in any way. However other substances are often used:<br />
<br />
* Talc<br />
* Grease (silicone is better - won't attack the plastic)<br />
* PTFE sprays<br />
* WD40 (not much good - but sometimes better than nothing)<br />
* Soap / washing up liquid<br />
<br />
(don't use graphite power - it conducts electricity!)<br />
<br />
===Push rods and sticks===<br />
Very useful for getting wires through awkward spaces. The simplest (and a widely used) stand in for "real" ones, are simply lengths of plastic conduit or trunking (and especially the lid off a bit of mini trunking!). The posher versions look rather like a narrow gauge version of a set of drain rods. Often made from fibreglass, they can be screwed together to make a very long stick (10m is not uncommon) and the end of the stick can be equipped with hooks and loops and other gizmos to make getting them round corners easier. <br />
<br />
One word or warning with the fibreglass sticks, wear gloves when handling them - otherwise you can get a nasty glass splinter!<br />
<br />
==Tools==<br />
The following is a big list of tools, some are essential, and some just handy to have. Essential in this case means these are tools that you need to do the job safely - you may be able to do it will less, but you may be putting yourself at risk when doing so. <br />
<br />
Many of the mechanical aspects of wiring have little to do with the things that one traditionally associates with the work of an electrician, and are really nothing more than general building and carpentry tasks. <br />
<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|-<br />
!Type<br />
!Description<br />
!Need<br />
|-<br />
| SDS Drill (3 function)<br />
<br />
| The ability to not only drill holes, but also quickly and neatly chisel out holes for socket boxes, and neat wall chases make the SDS drill a wonderful time saver. <br />
| Very Handy<br />
<br />
|-<br />
| Cordless drill / driver<br />
| In general cordless tools are very handy to have for electrical work since you will often be working in areas without power. Making holes, and fixing things in place probably come right near the top of list of tasks faced by anyone undertaking electrical work. A medium size (say 14.4V or better) combi drill is ideal for this sort of work. Having the hammer facility can make drilling holes into masonry for wall plugs far simpler. <br />
| Very Handy<br />
<br />
|-<br />
| Insulated screwdrivers (VDE) <br />
[[Image:VDEScrewdrivers.jpg]]<br />
| [http://www.ck-tools.com/Key_Ranges/sensoplus.htm VDE tools][1] are insulated and tested to to a high standard. This ensures that should the metal part of the tool make contact with live metalwork, no harm will come to the person holding the other end. These are absolutely essential when working on electrical installations. Not just for the rare occasions where live working is required, but the far more typical cases where one is working in close proximity to live circuits, or even on circuits that really ought to be dead, but are not!<br />
<br />
All things said and done, you can make do some ordinary screwdrivers for jobs not involving work on electrical fittings etc, and you may choose to buy a limited set of VDE insulated drivers: a medium<br />
phillips (typical for MCB terminals) and a small and medium flat blade for<br />
other terminals.<br />
| Essential<br />
|-<br />
|Side Cutters<br />
[[Image:SideCutters.jpg]]<br />
|VDE insulated side cutters are essential (one day, you *will* pick the wrong cable to cut). Side cutters are used for cutting cables and wire to length, and they are also often invaluable for stripping cables of their outer insulation. Some cutters also include specific facilities for wire stripping, [[http://www.ck-tools.com/Key_Ranges/pliers&cutters.htm eg]]. <br />
| Essential<br />
<br />
|-<br />
|Wire Strippers<br />
[[Image:EndStrippers.jpg]]<br />
|Good wire strippers make life very much simpler (while it is true that someone proficient with side cutters can often strip a wire quite satisfactorily with them as well, there is far more scope for bruised knuckles, damaged conductors, and tatty looking wire ends without them). The style of wire cutter is much a matter of personal preference. Side strippers are quick and easy to use - especially one smaller wires. The end action ones may be better for tough insulation found on the thicker and also special purpose wires. Some people also like to have an automatic wire stripper. These can make repeated stripping operations very much quicker. <br />
| Highly desirable<br />
<br />
|-<br />
|Combination pliers<br />
[[Image:CombinationPliers.jpg]]<br />
|regular square nosed medium set are useful for holding, bending, and twisting wires, tightening locknuts etc. In fact anywhere you need extra gripping power. <br />
| Handy<br />
<br />
|-<br />
|Long nose pliers<br />
[[Image:PointedNosePliers.jpg]]<br />
|A good pair of long nose pliers are the ideal tool for fishing wires out of awkward corners, and holding tricky wires in place as you tighten terminal screws. Note however that even with VDE insulated ones, care must be taken, since they have a large expanse of exposed metalwork that could easily short against live parts or earthed casework. <br />
| Very Handy<br />
<br />
|-<br />
|Ratchet action cable crimper<br />
[[Image:CrimpRatchetTool.jpg]]<br />
|Essential for making sound wire joints which will later become inaccessible, or where space is too restrictive to allow terminal (aka "choccie blocks") to be used. See the [[Cable crimping]] article for full details of how to use these. <br />
| Often Essential <br />
<br />
|-<br />
| 20mm Hole Saw<br />
[[Image:HoleSaw20mm.jpg]]<br />
| One of those universal truisms with many electrical accessories is that the "knock outs" are often in the wrong place, or failing that won't actually knock out without wrecking something. A small hole saw is the ideal way to persuade them of the error of their ways!<br />
| Handy<br />
<br />
|- <br />
| Metal, voltage, and stud detector<br />
[[Image:ZirconTriscannerPro.jpg]]<br />
| One of these that actually works (like the one pictured) is a massive time saver. It can find studs behind plasterboard, and buried pipes and cables (and tell you when they are live). Note the stud detection is defeated by foil backed plasterboard, but you can still use the metal detection facility to find the nails or screws that are holding it to the studs!<br />
| Well worth having<br />
<br />
|-<br />
<br />
<br />
<br />
|}<br />
<br />
[1] Just in case you were wondering what VDE stands for, the answer is: It wouldn't<br />
help much as the words are German! It is an internationally accredited German testing <br />
and standards institute. In their own words:<br />
<br />
''"The VDE Testing and Certification Institute is accredited on a national and <br />
''international level for the area of testing and certification of electrotechnical <br />
''equipment, components and systems. Testing of electrotechnical products is <br />
''conducted for safety, electromagnetic compatibility and other characteristics."''<br />
<br />
<br />
==Test gear==<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|-<br />
!Type<br />
!Description<br />
!Need<br />
|-<br />
| Multimeter<br />
[[Image:ClampMeter.jpg]]<br />
| A simple multimeter will be very handy for all sorts of tests, ranging from a simple "Is this wire live?" test, to checking continuity, and measuring cable resistances. <br />
<br />
(The clamp meter shown, also has the capability to measure the current flowing in a single wire (i.e. not a cable containing live and neutral, but either live '''or''' neutral in isolation) without needing to make any electrical connection to a circuit. Clamping this round the meter tails for example will let you read the total current draw on an installation with no risk)<br />
| Essential<br />
<br />
|-<br />
| Test lead extension<br />
[[Image:TestLeadExtender.jpg]]<br />
| Very handy for working out which socket is connected to which and various other tests that require you to measure continuity between more distant points. A workable alternative can be knocked up from any bit of cable or flex, but the proper lead is so much easier to use. <br />
| Handy<br />
<br />
|-<br />
| Volt stick<br />
| A simple non contact indicator that detects the presence of mains voltage on a wire. These are very good testing that a wire is safe to cut etc, when working on partially isolated systems. <br />
<br />
(Note for safety, it is always wise to test the volt stick on a known live circuit both before and after testing the wire you want to know the status of. This protects you from a freak accident should the detector fail at an in opportune moment!)<br />
| Very Handy<br />
<br />
|-<br />
| Socket Tester<br />
[[Image:SocketTester.jpg]]<br />
| A simple plug in tester that will indicate a wide range of potential faults with sockets and their wiring. Very quick and easy to use, and unlike probing about in the back of a socket with your multimeter, or trying to find a suitable appliance to plug into a socket to test it, much safer!<br />
| Very Handy<br />
<br />
|}<br />
<br />
==Advanced test gear==<br />
For anything other than basic alterations and additions to existing circuits, some more sophisticated test equipment is really required. These items can be bought as separate units or as an integrated tester that combines all the functions. Again, you will probably live if you don't use this kit, but it is the only way you are actually going to '''prove''' that your wiring is performing as it should)<br />
<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|-<br />
!Type<br />
!Description<br />
|-<br />
| Insulation resistance tester ("megger")<br />
[[Image:InsulationTester.jpg]]<br />
| These are often multi function devices that measure wire resistances with good accuracy, and are also able to perform resistance measurements using a very high test voltage (e.g. 500V or more). This will detect any part of a circuit (or whole installation) that has failing or damaged insulation. These can be very handy for finding tricky faults causing [http://wiki.diyfaq.org.uk/index.php?title=RCD#Nuisance_trips nuisance tripping] of RCDs for example. <br />
<br />
Great care must be taken with these devices. Firstly they '''will''' give you a shock if you hold the probes and push the test button. Secondly, you need to make sure there is nothing connected to the circuit under test that might be damaged by the high test voltage (some RCDs, Dimmers, and electronic power supplies etc)<br />
<br />
|-<br />
| Earth loop impedance tester<br />
[[Image:LoopTester.jpg]]<br />
| These are very useful devices that will allow you to measure the earth fault loop impedance at any socket in a circuit. This lets you prove the effectiveness of the earth, and establish data you will need for circuit design. They can also be used to measure the performance of earth rods. In many cases they will also let you measure the Prospective Short Circuit current and the Prospective Fault Current of a circuit. <br />
<br />
Older devices like the one pictured, perform tests using a fairly substantial test current. This is good in the sense that it proves that the earth really does work under simulated "fault" conditions, but has the downside of tripping any RCD protecting the circuit under test. More modern devices also have the capability of carrying out non tripping tests. <br />
<br />
|-<br />
| RCD Tester<br />
[[Image:RCDTester.jpg]]<br />
| About the only realistic way to properly test a RCD. These inject a user selectable earth leakage into a circuit, and then time how long (in 1/1000ths of seconds) it takes the RCD to disconnect the power. More sophisticated versions can also carry out "ramp" tests that slowly increase the leakage until the trip point is found. <br />
<br />
Not only required for RCD tests, they can often help establish the cause of nuisance trips.<br />
<br />
|}<br />
<br />
<br />
<br />
==Good workmanship==<br />
Take care of your wires and they will last longer and give less potential problems in the future. <br />
<br />
===Mechanical protection===<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|-<br />
!Type<br />
!Description<br />
|-<br />
| Capping || to protect cables from damage by plastering trowels, capping is ideal (plastic or metal). The advantage of capping over conduit is that it is easy to fit after a cable has been installed, and it won't affect the cable's ability to lose heat. <br />
|-<br />
<br />
| Plastic Conduit || Plastic conduit can be used for added protection to surface run cables. Note it is not well suited to burial since it offers little protection from drills, nails and screws, while lowering the current carrying capacity of the cable. <br />
|-<br />
<br />
| Metal conduit || Metal conduit can be buried, and also (if installed correctly) can be used as the circuit protective conductor (i.e. "earth"). It also offers good protection against penetration. It can also be surface run and offers good protection in harsh service conditions. Metal conduit is not however easy to use, since it requires additional tooling to bend, cut and thread the sections. The installation also needs to be carefully designed, to enable all the cables (or 'singles') in one section of conduit to be drawn through in one pass, and to ensure that cables are not drawn through more than the permitted maximum number of bends or corners (usually equivalent to 2 x 90 degree). Regulations require that all conduit is in place and continuous before drawing in cables. <br />
|-<br />
<br />
| Grommets [[Image:Gromets.jpg]] || Rubber grommets should be used anywhere a cable passes through a hole in a metal enclosure or back box. These will stop the insulation being damaged by sharp edges (not only from movement of the cable during installation, but also from movement caused by vibration or thermal expansion effects in use).<br />
|-<br />
<br />
| Strain relief sleeves || Sleeving can help protect flexes and cables at any point they will be subject to stress caused by carrying their own weight from a suspension point. <br />
|-<br />
<br />
| Glands || When attempting to make a cable entry or exit waterproof, or when working with cables that must be terminated with glands like [[Terminating SWA|SWA]], glands must be used. These not only fix the cable in place but also offer the water protection required, strain relief and often a facility to connect the cable screen (where present) to earth.<br />
|-<br />
<br />
| Minimum bend radii || Care must be taken with cables, to not attempt to bend them too acutely, since this may cause damage. <br />
<br />
|-<br />
<br />
|}<br />
<br />
===Labelling and identification===<br />
A well labelled installation is one of the signs of a good one! Things like:<br />
<br />
* Clear labels on the CU to identify what is protected by each fuse or breaker. <br />
<br />
* Identify main switches<br />
<br />
* Make sure earth and equipotential bonding conductors have the "Safety electrical connection - do not remove" tag on them. <br />
<br />
* Identify main equipotential bonds (gas, water etc)<br />
<br />
* Make sure any wires that are being used in a non obvious way or contrary to the expected use based on their colour, are sleeved with appropriate coloured tape or sleeving. e.g. the switched live returning from a light switch is carried in the black/blue insulated wire, it should be flagged with red/brown at '''both''' ends (you will curse the installer, the next time you remove a ceiling rose, and then notice no marking on the switch wire!)<br />
<br />
<br />
===Support===<br />
<br />
* Clips<br />
* Trunking<br />
<br />
<br />
<br />
==Making good==<br />
Once you have installed and tested all your new wiring, there is the rather more mundane task of filling all the wholes, and reinstating the fabric of the building before you lose too many household pets or children into floor voids or incur the wrath of the style police!<br />
<br />
===Filling chases===<br />
Bonding plaster is cheap and easy. Fill just below the surface to allow a final skim of filler or multifinish plaster. If the wall is old and crumbly, then paint some dilute PVA in the chase first, to stop it sucking all the water out of the plaster. <br />
<br />
Try and avoid getting wet plaster into the back of switches and sockets (or you might find out just how well those RCDs work!)<br />
<br />
If the cables keep popping out of the chase, then the occasion well positioned wide headed clout nail (beside the cable, not through it!), or dab of grab adhesive will keep things in place until the plaster has time to set. Old plaster is ideal for this - it sets faster. <br />
<br />
===Replacing floor boards===<br />
Nail or screw them. If you think they will need to come up again, use screws (they will probably squeak less as well). Where you have had to make cuts that are not over joists, you will need to include additional support. A short length of 2" x 2" screwed to the side of the joist can take the end of a board. <br />
<br />
<br />
==See also==<br />
* [[Rewiring Tips]]<br />
* [[:Category: Electrical]]<br />
* [[Special:Allpages|Wiki Contents]]<br />
* [[Special:Categories|Wiki Subject Categories]]<br />
<br />
<br />
[[Category: Electrical]]<br />
[[Category: Building]]</div>87.112.195.193https://wiki.diyfaq.org.uk/index.php?title=Electrical_Installation&diff=10062Electrical Installation2008-09-26T11:44:32Z<p>87.112.195.193: /* Lifting floors */ - concrete</p>
<hr />
<div>This article is all about the non engineering side of electrical installations. Its purpose is to explain some of the techniques that are used to when installing electrical equipment and wiring in typical domestic situations. <br />
<br />
{{Template:Under-construction}}<br />
<br />
==Cabling==<br />
Cables can be run in a large number of places and ways. However some places are better than others, and certain rules need to be followed to comply with the wiring regulations in some cases. In addition to the practical issues of cable routing, one also needs to think about what materials you are placing the cable in/under etc. since these may have effects that you need to take into account in the electrical design. E.g. a cable buried in an insulating material will not be able to lose heat as quickly as normal, and this means that the maximum current it is allowed to carry is reduced. <br />
<br />
===Wall chasing===<br />
Burying a cable in a wall is a traditional way to hide and protect the cable. Modern cables can be buried directly in plaster, or protected with capping before plastering. Before a cable can be buried however, a chase needs to be cut!<br />
<br />
See the [[wall chaser]] article for more detail on the options for cutting cable chases in plaster and masonry. <br />
<br />
Also don't forget the lazy option of using a pull switch rather than a wall mounted one, or a wireless room thermostat/door bell/network connection/etc in place of a wired one.<br />
<br />
====Getting past coving and skirtings====<br />
It is all well and good chasing a wall with your trusty SDS drill or wall chaser, but what happens when you reach some architectural feature that you don't want to go hacking through, like a deep skirting board or ornate plaster cornice or moulding?<br />
<br />
* Long drill bit: A very long drill bit (we are talking a minimum of 400mm here to get behind small items like picture or dado rails, or more realistically a stonking great 1m long bit bit for skirtings and coving!) can be a handy way to continue a chase behind the feature you are trying to avoid. Ideally one would need to drill straight up or down through the plaster to achieve this. This is usually impossible since you can't get the drill in the right place, or at the right angle since the wall is in the way. With small obstructions (dado etc) this may not matter, drilling down behind it at a slight angle will still be ok. For a longer vertical chase, the longer bit will be required. The trick here is to apply some sideways force to the bit as you drill. It should be possible to bend the drill such that its tip *is* parallel to the wall, while keeping the drill body and you hands at the slight angle required due to the obstruction of the wall. <br />
<br />
* Cranked gouging chisel: specially made SDS gouges can also work well for getting behind smaller items. <br />
<br />
* Using the other side of the wall: As simple as it sounds, in some cases the solution to avoiding difficult chases, might be to simply use the other side of the wall. This can be ideal for a cable chase on a tiled wall in a bathroom. It can also often save time where adjacent rooms have light switches "back to back" on the dividing wall - only one chase is required for the pair. Note One will need to take care that cable routes are within the prescribed zones expected - even if this means installing an extra accessory to mark the position.<br />
<br />
* A long threaded bar and a lump hammer. A long SDS bit may still damage very deep coving as it is not always possible to get the drill into a vertical position. A slightly bent threaded bar can be knocked up behind deep coving and not damage it<br />
<br />
===Under floors===<br />
Cables are also often taken under suspended floors or even sometimes placed into chases cut into concrete ones. <br />
<br />
====Lifting floors====<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|+ '''Techniques for lifting floors<br>'''<br />
|-<br />
!Type of floor<br />
!Methods<br />
|-<br />
| Traditional floorboards <br />
| A traditional boarded floor is one of the easier ones to get under! The traditional approach simply uses a pry bar and or bolster chisels to leaver it up. Sometimes you also need to cut a board. There are a number of approaches to this:<br />
<br />
* floorboard saw (one with a curved toothed section) will allow a plunge cut to be made over a joist.<br />
* Japanese style [http://www.axminster.co.uk/product-Ice-Bear-Japanese-Azebiki-Panel-Saw-20285.htm azebeki saws] are even better.<br />
* Bend 'n' saw - sometimes if the boards have enough bend in them, you can leaver one up in the middle of a section, and slide a chisel under it propped up on the adjacent boards. This will then let you at it with a traditional panel or tenon saw. <br />
* If you know the thickness of the boards, then you can snap off a jigsaw blade such that when the jigsaw is at the lowest part of its stroke, the blade is the same depth (or fractionally deeper) than the boards. If needs be a hold can be drilled to allow the blade some entry room.<br />
* If you are in a hurry, a [http://www.diyfaq.org.uk/powertools/circularsaw.htm plunge cut] with a circular saw - again with the depth set to no deeper than the board depth. <br />
* Oscillating multi-tools like the Fien Multimaster and the similar concept Bosch PMF 180, really come into their own here since they allow perfect neat plunge cuts into boards. The very narrow kerf of the blade also leaves far less visible damage once the floor is put back down again. <br />
<br />
|-<br />
| Tongue and groove floor boards || Similar to the above, except you will also have to rip cut through (or split off) the tongue on the board first, in order to be able to lift it. <br />
<br />
|-<br />
| Chipboard sheet <br />
| Generally far harder to work with since the boards are not only tongue and grooved at the edges, they are also large (typically 8' x 2'). In many modern houses, its also not uncommon for the partition walls to be built over the floor panels or at least the skirtings etc to be fixed over them. This can make removal of a whole board impossible. The best way to deal this this floor is to cut an access panel:<br />
<br />
* The Trend [http://www.axminster.co.uk/product-Trend-Routabout-Jig-23103.htm Routabout jig] is designed for this purpose, and makes it easy to not only get access, but also fix the hole afterwards. <br />
* The jigsaw, oscillating tool, and circular saw options described above also work. You will need to use screws and battens under the cut edges however to restore the strength of the floor afterwards (chipboard is string in gig sheets, but small strips are quite weak without support on all sides).<br />
<br />
|-<br />
| Laminate <br />
| While not easy it is possible to remove a plank of laminate in a floor. For the click together type, it may be simplest to start un-clicking panels at the edge of the room, and work your way back to where you need your access point. For glued panels, you will need to cut out a board. The way to do this is with a circular saw (preferably a small one - cordless ones are ideal). Set the cut depth to laminate thickness, and cut through the board all round close to its perimeter. Once the main bit is removed, use a chisel to break away the remaining edges from the adjacent boards.<br />
<br />
To replace the board you will need to cut away the underside section of the groove edges of the new plank, and then glue and lower the new board into place. Depending on how cleanly you were able to remove the tongue from the groove of the adjacent board, you may also need to cut this off the new board. <br />
<br />
|-<br />
| Concrete <br />
| Concrete floor screeds can be chased, but care should be taken. Many 'suspended' or 'block and beam' concrete floors are made from interlocking prefabricated components and are fully structural, and should not be chased without consulting the manufacturers or a structural engineer. When installing conduit in floors, consideration should be given to the possibility of condensation in the conduit draining to the lowest levels.<br />
<br />
|}<br />
<br />
====Entry via a ceiling====<br />
The lateral thinkers way to get under a "difficult" upstairs floor is via the ceiling of the room below. In many cases some new plasterboard and a bit of patching is a much quicker solution that lifting an engineered wood floor and underlay, or clearing a particularly cluttered room. <br />
<br />
====Joists====<br />
Most floors are held up by these. When they are running the direction you want your wire to go, all is well with the world and you have a nice easy job (mostly!) However, when you want to get across them, then life is more difficult! Many of the techniques listed elsewhere in this article for dealing with hollow walls can be applied to joists as well. However given they are holding your floors and ceilings up, you want to be a little careful how you go hacking them about. <br />
<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|+ '''Getting across joists<br>'''<br />
|-<br />
!Technique<br />
!Notes<br />
|-<br />
| Drilling <br />
| You can drill through the side of a joist. However you should only drill in the middle of the side, and not at the top or bottom, since the middle section has least stress on it. You should also not drill near to the ends of a joist, since this increases the possibility that the end of the joist could fail in "shear" (i.e. split along the length at the end, making the whole lot weaker). Another advantage of drilling the centre of the joist, is that your cables should be well away from any nails or screws. <br />
<br />
To meet current building regulations, the hole does not want to be more than 0.25 times the total joist height - so a 2" hole on a 8" joist is about the limit. It should also not go closer to the end of the joist than 1/4 of the span (so no nearer than 1m from the end of a 4m joist), and no closer to the centre than 0.4 times the span.<br />
<br />
Take care not to over stuff the holes, since you don't want to reduce the current carrying capacity of your cables by bunching lots of circuits together. <br />
<br />
If you need another hole, leave gap equal to at least three diameters between one and the next. <br />
<br />
The posh way to get between joists is with an angle drill:<br />
<br />
[[Image:AngleDrillLength.jpg]]<br />
<br />
Fitted with a short auger or a spade bit with part of the shaft cut down, these will get between most joists. However you may find a small cordless drill or an impact driver will also fit. If you can't get a drill in, then a long drill bit at an angle can be a last resort.<br />
<br />
|-<br />
| Notching<br />
| Notching is the process of hacking a lump out of the top of the joist (tenon saw and chisel, or oscillating saw being the easiest options here). Unlike drilling, this is better done at the ends of the joist and not near the middle of the span, since it weakens it in bending but not as much in shear. <br />
<br />
A notch should be no deeper than 1/8th of the joist depth (so 1" on a 8" deep joist is the limit).<br />
<br />
Notches must go between 0.07 and 0.25 times the span. So with a 4m joist that would be anywhere between 280mm and 1m from either end.<br />
<br />
Additional care must be taken to protect the cables from nails and screws. You can buy metal plates to place over the top of notches to achieve this. <br />
<br />
|}<br />
<br />
===Over Ceilings===<br />
In some cases the same as under a floor! However this also includes over false ceilings (which if you have lots of wires to hide or lots of ceiling piercing lights to install, may be well worth building for the purpose). It also includes through loft spaces. Once caution to watch is to keep modern PVC cable away from polystyrene insulation (the plasticiser leaches out of the PVC into the polystyrene, leaving a gooey mess, and rather brittle cable insulation)<br />
<br />
<br />
===In hollow walls===<br />
It is also sometimes possible to drop a wire down a hollow stud wall (either plasterboard or lath and plaster). Note it is not recommended to place wires in the cavity of exterior walls, where they could cause dampness bridging, and be adversely affected by cavity wall insulation injected at a later stage. <br />
<br />
Getting wires into a stud wall in the first place is easy to do when building it. However at a later date it is not as easy and you may meet a few obstacles:<br />
<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|+ '''Getting round problem walls<br>'''<br />
|-<br />
!Problem<br />
!Solutions<br />
|-<br />
<br />
<br />
|-<br />
| Catching a wire<br />
| Feeding a wire along the inside of a wall is one thing, but getting the free end out again without making a hand sized hole in the wall is another problem! Techniques to try include:<br />
<br />
* Standard retractable tape measure. Push a loop of this into the wall through a hole. If you keep feeding in tape, then inside the wall it will expand out against the sides etc. This makes a larger target to feed the wire through. Pulling the loop of tape back through the hole can then "snare" the cable. <br />
* The same trick also works (better) with a length of flexible plastic coated net curtain wire used as the loop.<br />
* A length of chain, can also make a good weight to pull a draw string through. It has the advantage of being easy to "catch" with a magnet or magnetic pick up tool. <br />
<br />
|-<br />
| Getting past studs and noggings<br />
| It is rather hard to drill a hole through the side of a lump of wood if all you can see is a board covering its front face! However there are ways:<br />
<br />
* Long drill bit. If you have a hole to work from (say a cutout for a socket box) then a long drill bit at an shallow angle can be used to get through at least one obstruction. Spade bits with an extension shaft or two can be very useful here since they let you make a big diameter hole at some distance. <br />
* Notching from the face. You can cut a notch in the face of a stud or nogging without causing too much damage to the face of the wall, by drilling a series of overlapping holes with a wide spade or auger bit. <br />
<br />
<br />
|}<br />
<br />
===Pull wires / cords / tapes===<br />
Ideal for getting wires through tortuous paths. There are specialist tapes and cords for the purpose, but almost any bit of string or even and old cable may be used. Fishing line is often very good in that it is strong, long, thin, slippery, and cheap! The real art with any pull string is how you get it into location in the first place! Some of the more imaginative options include:<br />
<br />
* Add a weight or ball to the end and throw, catapult, or otherwise propel it in the desired direction. A metal weight like a small bit of chain can make retrieving the end easy with a magnet on a stick. <br />
<br />
* Radio controlled cars and other self propelled toys, can be "driven" to the destination while towing a wire - handy for ground floor voids that are not big enough (or too full of rat crap) to make climbing under yourself desirable. <br />
<br />
* Small children can often be pressed into service with some bribery ;-)<br />
<br />
* Cat, cable tie, and a sardine might also work!<br />
<br />
There is a whole subset of these, for getting a pull cord through ducts and pipes. Most involve either a vacuum cleaner to suck something through the ducts, or a compressor to blow something through it. Rags, plastic bags, and tennis balls being tried and tested candidates. <br />
<br />
Also when pulling pull cords, you may need to allow for the possibility that all you will pull with the first cord is a stronger cord! Working your way up to the particularly heavy or stiff cable that ultimately needs to get through. <br />
<br />
One handy tip when laying in wires in many cases, is to pull a new cord through with each wire. That way you can always add more later. <br />
<br />
===Lubricants===<br />
Sometimes some extra assistance is needed when getting wires and cables through tight spaces and into pipes, ducts, conduits etc. There are specialist cable pulling lubricants available like "Yellow 77" that are designed for this purpose and won't hurt or react with the cable in any way. However other substances are often used:<br />
<br />
* Talc<br />
* Grease (silicone is better - won't attack the plastic)<br />
* PTFE sprays<br />
* WD40 (not much good - but sometimes better than nothing)<br />
* Soap / washing up liquid<br />
<br />
(don't use graphite power - it conducts electricity!)<br />
<br />
===Push rods and sticks===<br />
Very useful for getting wires through awkward spaces. The simplest (and a widely used) stand in for "real" ones, are simply lengths of plastic conduit or trunking (and especially the lid off a bit of mini trunking!). The posher versions look rather like a narrow gauge version of a set of drain rods. Often made from fibreglass, they can be screwed together to make a very long stick (10m is not uncommon) and the end of the stick can be equipped with hooks and loops and other gizmos to make getting them round corners easier. <br />
<br />
One word or warning with the fibreglass sticks, wear gloves when handling them - otherwise you can get a nasty glass splinter!<br />
<br />
==Tools==<br />
The following is a big list of tools, some are essential, and some just handy to have. Essential in this case means these are tools that you need to do the job safely - you may be able to do it will less, but you may be putting yourself at risk when doing so. <br />
<br />
Many of the mechanical aspects of wiring have little to do with the things that one traditionally associates with the work of an electrician, and are really nothing more than general building and carpentry tasks. <br />
<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|-<br />
!Type<br />
!Description<br />
!Need<br />
|-<br />
| SDS Drill (3 function)<br />
<br />
| The ability to not only drill holes, but also quickly and neatly chisel out holes for socket boxes, and neat wall chases make the SDS drill a wonderful time saver. <br />
| Very Handy<br />
<br />
|-<br />
| Cordless drill / driver<br />
| In general cordless tools are very handy to have for electrical work since you will often be working in areas without power. Making holes, and fixing things in place probably come right near the top of list of tasks faced by anyone undertaking electrical work. A medium size (say 14.4V or better) combi drill is ideal for this sort of work. Having the hammer facility can make drilling holes into masonry for wall plugs far simpler. <br />
| Very Handy<br />
<br />
|-<br />
| Insulated screwdrivers (VDE) <br />
[[Image:VDEScrewdrivers.jpg]]<br />
| [http://www.ck-tools.com/Key_Ranges/sensoplus.htm VDE tools][1] are insulated and tested to to a high standard. This ensures that should the metal part of the tool make contact with live metalwork, no harm will come to the person holding the other end. These are absolutely essential when working on electrical installations. Not just for the rare occasions where live working is required, but the far more typical cases where one is working in close proximity to live circuits, or even on circuits that really ought to be dead, but are not!<br />
<br />
All things said and done, you can make do some ordinary screwdrivers for jobs not involving work on electrical fittings etc, and you may choose to buy a limited set of VDE insulated drivers: a medium<br />
phillips (typical for MCB terminals) and a small and medium flat blade for<br />
other terminals.<br />
| Essential<br />
|-<br />
|Side Cutters<br />
[[Image:SideCutters.jpg]]<br />
|VDE insulated side cutters are essential (one day, you *will* pick the wrong cable to cut). Side cutters are used for cutting cables and wire to length, and they are also often invaluable for stripping cables of their outer insulation. Some cutters also include specific facilities for wire stripping, [[http://www.ck-tools.com/Key_Ranges/pliers&cutters.htm eg]]. <br />
| Essential<br />
<br />
|-<br />
|Wire Strippers<br />
[[Image:EndStrippers.jpg]]<br />
|Good wire strippers make life very much simpler (while it is true that someone proficient with side cutters can often strip a wire quite satisfactorily with them as well, there is far more scope for bruised knuckles, damaged conductors, and tatty looking wire ends without them). The style of wire cutter is much a matter of personal preference. Side strippers are quick and easy to use - especially one smaller wires. The end action ones may be better for tough insulation found on the thicker and also special purpose wires. Some people also like to have an automatic wire stripper. These can make repeated stripping operations very much quicker. <br />
| Highly desirable<br />
<br />
|-<br />
|Combination pliers<br />
[[Image:CombinationPliers.jpg]]<br />
|regular square nosed medium set are useful for holding, bending, and twisting wires, tightening locknuts etc. In fact anywhere you need extra gripping power. <br />
| Handy<br />
<br />
|-<br />
|Long nose pliers<br />
[[Image:PointedNosePliers.jpg]]<br />
|A good pair of long nose pliers are the ideal tool for fishing wires out of awkward corners, and holding tricky wires in place as you tighten terminal screws. Note however that even with VDE insulated ones, care must be taken, since they have a large expanse of exposed metalwork that could easily short against live parts or earthed casework. <br />
| Very Handy<br />
<br />
|-<br />
|Ratchet action cable crimper<br />
[[Image:CrimpRatchetTool.jpg]]<br />
|Essential for making sound wire joints which will later become inaccessible, or where space is too restrictive to allow terminal (aka "choccie blocks") to be used. See the [[Cable crimping]] article for full details of how to use these. <br />
| Often Essential <br />
<br />
|-<br />
| 20mm Hole Saw<br />
[[Image:HoleSaw20mm.jpg]]<br />
| One of those universal truisms with many electrical accessories is that the "knock outs" are often in the wrong place, or failing that won't actually knock out without wrecking something. A small hole saw is the ideal way to persuade them of the error of their ways!<br />
| Handy<br />
<br />
|- <br />
| Metal, voltage, and stud detector<br />
[[Image:ZirconTriscannerPro.jpg]]<br />
| One of these that actually works (like the one pictured) is a massive time saver. It can find studs behind plasterboard, and buried pipes and cables (and tell you when they are live). Note the stud detection is defeated by foil backed plasterboard, but you can still use the metal detection facility to find the nails or screws that are holding it to the studs!<br />
| Well worth having<br />
<br />
|-<br />
<br />
<br />
<br />
|}<br />
<br />
[1] Just in case you were wondering what VDE stands for, the answer is: It wouldn't<br />
help much as the words are German! It is an internationally accredited German testing <br />
and standards institute. In their own words:<br />
<br />
''"The VDE Testing and Certification Institute is accredited on a national and <br />
''international level for the area of testing and certification of electrotechnical <br />
''equipment, components and systems. Testing of electrotechnical products is <br />
''conducted for safety, electromagnetic compatibility and other characteristics."''<br />
<br />
<br />
==Test gear==<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|-<br />
!Type<br />
!Description<br />
!Need<br />
|-<br />
| Multimeter<br />
[[Image:ClampMeter.jpg]]<br />
| A simple multimeter will be very handy for all sorts of tests, ranging from a simple "Is this wire live?" test, to checking continuity, and measuring cable resistances. <br />
<br />
(The clamp meter shown, also has the capability to measure the current flowing in a single wire (i.e. not a cable containing live and neutral, but either live '''or''' neutral in isolation) without needing to make any electrical connection to a circuit. Clamping this round the meter tails for example will let you read the total current draw on an installation with no risk)<br />
| Essential<br />
<br />
|-<br />
| Test lead extension<br />
[[Image:TestLeadExtender.jpg]]<br />
| Very handy for working out which socket is connected to which and various other tests that require you to measure continuity between more distant points. A workable alternative can be knocked up from any bit of cable or flex, but the proper lead is so much easier to use. <br />
| Handy<br />
<br />
|-<br />
| Volt stick<br />
| A simple non contact indicator that detects the presence of mains voltage on a wire. These are very good testing that a wire is safe to cut etc, when working on partially isolated systems. <br />
<br />
(Note for safety, it is always wise to test the volt stick on a known live circuit both before and after testing the wire you want to know the status of. This protects you from a freak accident should the detector fail at an in opportune moment!)<br />
| Very Handy<br />
<br />
|-<br />
| Socket Tester<br />
[[Image:SocketTester.jpg]]<br />
| A simple plug in tester that will indicate a wide range of potential faults with sockets and their wiring. Very quick and easy to use, and unlike probing about in the back of a socket with your multimeter, or trying to find a suitable appliance to plug into a socket to test it, much safer!<br />
| Very Handy<br />
<br />
|}<br />
<br />
==Advanced test gear==<br />
For anything other than basic alterations and additions to existing circuits, some more sophisticated test equipment is really required. These items can be bought as separate units or as an integrated tester that combines all the functions. Again, you will probably live if you don't use this kit, but it is the only way you are actually going to '''prove''' that your wiring is performing as it should)<br />
<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|-<br />
!Type<br />
!Description<br />
|-<br />
| Insulation resistance tester ("megger")<br />
[[Image:InsulationTester.jpg]]<br />
| These are often multi function devices that measure wire resistances with good accuracy, and are also able to perform resistance measurements using a very high test voltage (e.g. 500V or more). This will detect any part of a circuit (or whole installation) that has failing or damaged insulation. These can be very handy for finding tricky faults causing [http://wiki.diyfaq.org.uk/index.php?title=RCD#Nuisance_trips nuisance tripping] of RCDs for example. <br />
<br />
Great care must be taken with these devices. Firstly they '''will''' give you a shock if you hold the probes and push the test button. Secondly, you need to make sure there is nothing connected to the circuit under test that might be damaged by the high test voltage (some RCDs, Dimmers, and electronic power supplies etc)<br />
<br />
|-<br />
| Earth loop impedance tester<br />
[[Image:LoopTester.jpg]]<br />
| These are very useful devices that will allow you to measure the earth fault loop impedance at any socket in a circuit. This lets you prove the effectiveness of the earth, and establish data you will need for circuit design. They can also be used to measure the performance of earth rods. In many cases they will also let you measure the Prospective Short Circuit current and the Prospective Fault Current of a circuit. <br />
<br />
Older devices like the one pictured, perform tests using a fairly substantial test current. This is good in the sense that it proves that the earth really does work under simulated "fault" conditions, but has the downside of tripping any RCD protecting the circuit under test. More modern devices also have the capability of carrying out non tripping tests. <br />
<br />
|-<br />
| RCD Tester<br />
[[Image:RCDTester.jpg]]<br />
| About the only realistic way to properly test a RCD. These inject a user selectable earth leakage into a circuit, and then time how long (in 1/1000ths of seconds) it takes the RCD to disconnect the power. More sophisticated versions can also carry out "ramp" tests that slowly increase the leakage until the trip point is found. <br />
<br />
Not only required for RCD tests, they can often help establish the cause of nuisance trips.<br />
<br />
|}<br />
<br />
<br />
<br />
==Good workmanship==<br />
Take care of your wires and they will last longer and give less potential problems in the future. <br />
<br />
===Mechanical protection===<br />
{| border="1" cellpadding="6" cellspacing="0" style="text-align:left"<br />
|-<br />
!Type<br />
!Description<br />
|-<br />
| Capping || to protect cables from damage by plastering trowels, capping is ideal (plastic or metal). The advantage of capping over conduit is that it is easy to fit after a cable has been installed, and it won't affect the cables ability to lose heat. <br />
|-<br />
<br />
| Plastic Conduit || Plastic conduit can be used for added protection to surface run cables. Note it is not well suited to burial since it offers little protection from drills, nails and screws, while lowering the current carrying capacity of the cable. <br />
|-<br />
<br />
| Metal conduit || Metal conduit can be buried, and also (if installed correctly) can be used as the circuit protective conductor (i.e. "earth"). It also offers good protection against penetration. It can also be surface run and offers good protection in harsh service conditions. Metal conduit is not however easy to use, since it requires additional tooling to bend, cut and thread the sections. <br />
|-<br />
<br />
| Grommets [[Image:Gromets.jpg]] || Rubber grommets should be used anywhere a cable passes through a hole in a metal enclosure or back box. These will stop the insulation being damaged by sharp edges. (not only from movement of the cable during installation, but also from movement caused by vibration or thermal expansion effects in use).<br />
|-<br />
<br />
| Strain relief sleeves || Sleeving can help protect flexes and cables at any point they will be subject to stress caused by carrying their own weight from a suspension point. <br />
|-<br />
<br />
| Glands || When attempting to make a cable entry or exit waterproof, or when working with cables that must be terminated with glands like [[Terminating SWA|SWA]], glands must be used. These not only fix the cable in place but also offer the water protection required, strain relief and often a facility to connect the cable screen (where present) to earth.<br />
|-<br />
<br />
| Minimum bend radii || Care must be taken with cables, to not attempt to bend them too acutely, since this may cause damage. <br />
<br />
|-<br />
<br />
|}<br />
<br />
===Labelling and identification===<br />
A well labelled installation is one of the signs of a good one! Things like:<br />
<br />
* Clear labels on the CU to identify what is protected by each fuse or breaker. <br />
<br />
* Identify main switches<br />
<br />
* Make sure earth and equipotential bonding conductors have the "Safety electrical connection - do not remove" tag on them. <br />
<br />
* Identify main equipotential bonds (gas, water etc)<br />
<br />
* Make sure any wires that are being used in a non obvious way or contrary to the expected use based on their colour, are sleeved with appropriate coloured tape or sleeving. e.g. the switched live returning from a light switch is carried in the black/blue insulated wire, it should be flagged with red/brown at '''both''' ends (you will curse the installer, the next time you remove a ceiling rose, and then notice no marking on the switch wire!)<br />
<br />
<br />
===Support===<br />
<br />
* Clips<br />
* Trunking<br />
<br />
<br />
<br />
==Making good==<br />
Once you have installed and tested all your new wiring, there is the rather more mundane task of filling all the wholes, and reinstating the fabric of the building before you lose too many household pets or children into floor voids or incur the wrath of the style police!<br />
<br />
===Filling chases===<br />
Bonding plaster is cheap and easy. Fill just below the surface to allow a final skim of filler or multifinish plaster. If the wall is old and crumbly, then paint some dilute PVA in the chase first, to stop it sucking all the water out of the plaster. <br />
<br />
Try and avoid getting wet plaster into the back of switches and sockets (or you might find out just how well those RCDs work!)<br />
<br />
If the cables keep popping out of the chase, then the occasion well positioned wide headed clout nail (beside the cable, not through it!), or dab of grab adhesive will keep things in place until the plaster has time to set. Old plaster is ideal for this - it sets faster. <br />
<br />
===Replacing floor boards===<br />
Nail or screw them. If you think they will need to come up again, use screws (they will probably squeak less as well). Where you have had to make cuts that are not over joists, you will need to include additional support. A short length of 2" x 2" screwed to the side of the joist can take the end of a board. <br />
<br />
<br />
==See also==<br />
* [[Rewiring Tips]]<br />
* [[:Category: Electrical]]<br />
* [[Special:Allpages|Wiki Contents]]<br />
* [[Special:Categories|Wiki Subject Categories]]<br />
<br />
<br />
[[Category: Electrical]]<br />
[[Category: Building]]</div>87.112.195.193