taaldar Lots of useful information for anyone due to rewire.
The basic electrical installation design is fairly much decided by the 16th edition wiring regs, so unless you get into specialist, unusual or illegal territory, many of the choices are already made for you.
You're still left with quite a lot of details to choose from. These details can affect comfort, safety, reliability, and avoid unnecessary trouble and expense. In sum these many details can make quite a difference. A lot of good choices can be made at little or no cost, and several will save money.
The Basic System
You'll get 30A rings supplying the sockets, or occasionally 20A radials. You'll get 6A lighting circuits, or occasionally 10A. You'll get dedicated feeds for cooker and shower if you've got those, or the oven might end up on a 13A plug.
You'll usually get 1 RCD, which in a small minority of cases can produce a lot of frustration by frequently taking out the power.
CU: consumer unit, the modern version of a fusebox.
Split load CU: A CU divided into 2 halves, each with its own main switch. A good idea. It means power can stay on no matter what happens to one section of the wiring. Even during a partial rewire half the power can stay on.
MCB: a pushbutton overcurrent trip found in the consumer unit. This replaces a fuse. Rewirable fuses are still fully compliant with today's wiring regs. Contrary to popular myth, MCBs are not a significant safety benefit for general use, but they are easier to reset. Where they are a safety plus is when householders can be expected to be irresponsible, eg rented property. MCBs should be chosen in these cases, as rewirable fuses are easy to abuse.
RCD: earth leakage trip found in the consumer unit. This will trip if earth leakage current is too high, and reduces the risk of electrocution. Unfortunately they're known for nuisance trips. The majority of older installs have no RCD.
TT: a type of earthing that uses a local earth rod. TT installations must include a "Whole House RCD", since an earth rod alone is inadequate to clear faults. Whole house RCDs are better avoided with other installation types, as they're a known source of problems in some cases.
Now some ideal choices. Many will add a bit to installation cost, but are well worth it. Many cost nothing extra, and a few cost a lot. One can make many good choices without adding a lot to the cost.
Split Load CU
Use of a split load CU means one half of your wiring can be turned off while the other half stays on. So whatever may happen with your electrical system*, you don't need to turn it all off. This enables you to have power in the event of a fault, and to have power while working on the installation itself. Split load CUs are common today, but not always used. Typical extra cost: Â£0
*there are exceptions of course, such as lightning strike or a major fire.
What you don't want is the default install of one RCD supplying half or even the whole house. Most of these work OK, but some create no end of frustration, trouble and expense for the householder. For Â£35-Â£100 more you can have 2 or 3 RCBOs instead of one RCD, which eliminates many RCD nuisance trips, and minimises the consequences of any that do occur. This way if an RCBO trips, you lose power to one socket circuit instead of all power.
Unless you have a TT earthing system, lighting should not be on an RCD*. Lighting circuits have not proven to be a significant electrocution risk. RCDs tend to cause lighting to fail early in a fire, and this has resulted in the death of people failing to escape. Lighting is not usually on RCD**, but many such setups are in use. Unfortunately the coming 17th edition is expected to mandate RCDs on all lighting circuits.
* except that regs now mandate an RCDed feed for bathroom lighting on new installs
Dedicated Freezer Feed
A freezer is best put on its own dedicated feed, so other appliance faults don't stop it working and ruin Â£Â£Â£ of food and days of your cooking efforts, or risk food poinsoning. This is a much bigger issue with new rewires than it has been in the past, as RCDs are easily tripped.
The risks of food poisoning far outweigh those of shock from freezers, so no RCD on the freezer supply is the better option.
- To meet 16th edn regs, this means the socket for the freezer should not be likely to be used by outdoor tools, so don't put the socket by the back door.
- To meet 17th edition, either an RCD must be fitted, or the cable buried 2" deep, or capping fitted to the whole cable run.
You need enough. Double sockets are not adequate by themselves to run the amount of electronics we use today (the last socket I put in was a 12 way). On the other hand, installing large numbers of fixed sockets is an eyesore and expensive. Doubles are enough if you sprinkle them around the room, and don't mind using several 4 & 6 way extension leads.
Halogen downlighters are popular today, but have some downsides. They're expensive to run, are one of the most energy inefficient options available, heat the house up in summer, they make lying right back in your own home truly uncomfortable, and they tend to give uneven illumination and glare. Halogen lights are also the type most capable of starting fires, and most halogen downlighters pierce the ceiling plasterboard fire and smoke barrier. There are approx 69,000 house fires per year in the UK.
Its a good idea to calculate run costs before installing halogen, to avoid regret. As an example, 500w of halogen downlighters on 6 hours a day would cost Â£65 per year per room in electricity, plus 12-24 bulb replacements per year at Â£1 each, making a total cost of Â£77 per room per year. 4 rooms of this would equal Â£308 per year, or Â£9000 per 30 year product life*. For comparison, a similar level of CFL lighting would cost around Â£2000. (The exact amount will depend how much you install.) For some people that cost is fine, but for some its not the best way to spend the money.
For those that want the look of halogen without the energy use, there is the option to use lower power halogen downlighters, eg 5w, 10w or 20w, making up the rest of the light level with more efficient light sources, such as uplighting or concealed lighting.
Below 150w, mains voltage halogens are less efficient and less reliable than 12v halogen. Mains bulbs are lower efficiency compared to low voltage ones, more fragile, shorter lived, and more susceptible to early failures. They're also more cost per bulb. Low voltage does cost slightly more to install, but the extra cost is repaid many times over in use.
* Its actually more complex than that, and needs to be calculated for each case. The figure given just gives some idea of what those new halogen fittings will really cost.
Fitting switchbanks where possible improves comfort and reduces electricity bills a little. These are 2 or more switches in the one box, where one would traditionally find a single switch. Each switch controls some of the lighting. Thus it is easy to control lighting brightness. Cost is about Â£1 more per switch point, and they typically save this much in under a year.
Using dimmers to achieve a similar result results in much greater electricity use, as bulb efficiency falls very rapidly with dimming. It may also cause practical problems if filament bulbs are banned, which looks fairly likely, as dimmers are incompatible with most other lamp types.
Uplighting uses the ceiling as a large diffuse source of light for the room. This gives less shadows and dark spots and more even illumination, than other lighting types, and better energy efficiency than downlighting. With white ceilings of at least normal height, uplighting is a good approach to general lighting.
For uplighting, spotlight fittings with ordinary GLS bulbs or CFLs in (not spotlight bulbs) are effective, look good, work well, and minimise bulb cost. Such fittings need to shroud the bulb. For large uplighters, PAR38 spotlight fittings that wrap around the bulb work well, again using GLS or CFL bulbs, not PARs.
Plaster uplighters are not recommended, really they're inappropriate for uplighting. They create a high intensity light patch on the wall, which uplighting is intended to avoid. They light the wall from such a shallow angle as to magnify and illuminate even the tiniest blemish, making the wall look a mess.
Halogen uplighters are a particular risk, they quickly ignite any paper or plastic that lands on them, or that they land on, and there are already too many deaths in house fires. They are not recommended.
Kitchen worktop lighting
Mini fluorescent strips are a good idea, but are sometimes supplied with less than pleasant bulbs, such as 4000K. Fluorescent gives good even illumination, but beware of going overboard on light level, and check the points above for a good fl lighting installation.
Halogen worktop lighting is prone to causing glare.
Tubular filament lighting is especially energy inefficient, much more so than GLS filament lighting. Hence it produces more heat than other lighing types, often discolouring kitchen units and heating stored food. Tubular filament lights also have safety issues. As well as both ends being open to touch, one of which is live, if you touch one end of the tube while inserting the other you can get a shock, and this is easy to do if not paying full attention for a moment.
CFL worktop lighting is cheaper to install than linear fluorescent in cases where there is enough room to fit them. The lightspread is not quite as even as linear fl, but one significant advantage is that the end user can easily adjust the light level to suit personal preference by replacing bulbs with different wattages.
Fluorescent Lighting can look good if chosen and installed well. But the all too common choice of a bare bulbed butt ugly glowstart fitting in the centre of the room with a tube chosen at random is a recipe for unpleasant lighting.
Good fluorescent lighting needs the following points:
1 Hidden fittings & hidden bulb.
3 comfortable light level.
4 No flicker and flash
5 A tube of respectable quality. I like 3500K tubes, there are several good types to choose from, but there are also many unpleasant or poor quality types of tube on the market.
6 Spare tubes of a size that makes keeping a spare practical.
For 1 & 2 - trough fittings are effective.
For 3 - fluorescent lighting should be around a quarter of the power you would use with filament bulbs.
For 4 - An electronic ballast fitting avoids all the flicker and flash of cheaper glowstart fittings.
For 5 - see the next section
For 6 - 2 foot tubes are easiest to store, 4' are next best. Larger tubes provide more light in one place than is usually wanted for domestic use, and spares take a lot of space to store.
Fluorescent tube types
Fluorescent tubes come in many different versions of white, ranging from excellent quality to dire. Buying tubes at random is liable to give unsatisfactory lighting. Tubes are normally marked with their colour on on the glass at one end. Many shop assistants are unaware that there are different versions of white, or that the tubes are thus marked, you generally have to look for yourself.
Tubes marked simply as 'white' are not of the best quality, though not the worst. I can recommend 2700K and 3500K tubes work well in domestic settings. Higher colour temperature tubes appear too cold or harsh for general household use.
2700K is the colour of GLS filament bulbs, so it matches traditional filament lighting. 2700K is a warm white with a slight tendency to yellowiness. 2700K is less efficient than cooler tints, and not stocked in most shops. 2700K triphosphor is the tube of choice where the fluorescent lighting must take on the character of filament lighting.
3000K is the colour temperature of many halogen bulbs, cleaner and crisper than 2700K. Some 3000K fluorescent tubes don't have good CRI*, so if you want 3000K to match halogen its best to pick the more expensive triphosphor tubes rather than halophosphates.
3500K will not match other light sources, unless they're also 3500K fluorescent, but used alone they give a clean fresh look. These are my favourite halophosphate tubes for domestic lighting.
4000K: cold, harsh and anaemic, and 4500K and up are like the old fashioned 'cool white' tubes that once gave fluorescent lighting such a bad reputation.
There are also proprietary numbering systems, such as the Philips system.
Cool white and 'daylight' are ill suited to domestic use.
* CRI = colour rendering index, a measurement of how well fluorescent tubes render colour. 100 is perfect, 50 is grim. Triphosphor tubes have higher CRI than halophosphate, but cost more.
For more information see Fluorescent Lighting
Filament Strip Lights
Filament strip bulbs are around a foot long, and rated 30w and 60w. The fittings are very cheap to buy, but have particularly poor energy efficiency, unnecessarily high run cost, and the bulbs need frequent replacement.
Both ends of the fitting are open to touch when the bulb is removed, one end is live when on, and also often live when off.
These lights also suffer from their own particular safety problem. When inserting a bulb, if you touch the end of the tube that is out of the fitting, you have a 50% chance of being personally connected to the mains. This is due to a few factors with these fittings that combine to make them of poor safety.
There are 2 ways this can happen. Firstly relamping while switched on gives this scenario a 50/50 probability of causing electric shock, and its very easy to end up with a finger on the wrong part of the bulb, it only takes a brief moment of paying attention to something else.
Secondly, relamping is not always safe while switched off either, as the fittings frequently use non-polarised connectors with single pole switches, as well as having the bare live end and conductive tube with separated connections problems.
Tubular filament lamps were in use in the 1920s, and with nothing but disadvantages compared to any other lighting type, their time is up. Fluorescent strips will have much lower power ratings, since they're several times more efficient, and won't fry the kids.
Kitchen worktop lighting
Fluorescent gives good even illumination, but beware of going overboard on light level, and check the points above for a good fl lighting installation.
Halogen worktop lighting is prone to causing glare.
Tubular filament lighting is especially energy inefficient, and runs hot, sometimes discolouring kitchen units and heating stored food. Tubular filament lights also have safety issues explained above.
CFL worktop lighting is cheaper to install than linear fluorescent in cases where there is enough room to fit them. The lightspread is not as even as linear fl, but the end user can easily adjust the light level to suit personal preference by replacing bulbs.
It is a wise idea to arrange stair lighting so that the failure of any one light does not jeopardise safety. Stairs cause many injuries & fatalities each year. If lights have overlapping lighting areas, the loss of one light is not a real problem.
Installing stair lights out of reach is unwise, this is a recipe for a serious accident, inconvenient, and a poor design choice common in times past. It causes falls down stairs while replacing bulbs, delays in bulb replacement, and the elderly and chronically infirm are too often ripped off with exorbitant charges for simply replacing a lightbulb that they can't reach (eg Â£50 callout charge). And most of us will be elderly one day.
Connecting different stair lights to different lighting circuits ensures lighting stays in service if/when one of the circuits trips. When there is only one stair light, it can be connected to a different circuit to whichever other light fitting gives the most light to the stairs.
Stairwells with no windows benefit from battery backup lights (as used for fire escape). Non-maintained units only come on when power is lost, and cost around Â£17.
Such a light fitted by the CU is also a nice option when money is no object, but a torch or candle fumbled for in the dark is cheaper.
Lighting can be on type C MCBs rather than the more common type B. Some installs suffer frequent nuisance trips when bulbs blow, the risk of this is possibly a little lower with a type C or D MCB. Care should be taken to ensure the circuit is tested and figures compared with those in the current edition of BS7671 for maximum Zs. MCBs of either type cost around Â£6 each, and the average 2.5 bed house will have 2 or maybe 3 lighting MCBs.
Lighting circuits on rewirable or HRC fuses pretty much eliminate the false trip problem, but rewirable fuses can be abused by irresponsible people, so these are better avoided in rented accomodation etc.
Light Switch Controls Plugged in Lamps
It is possible at extra cost to provide wall sockets powered by the wall lightswitch, so standard lamps and table lamps all switch off in one go. Due to technical & legislative issues these will usually be 2A or 5A round pin sockets.
A round pin plug can be fitted to the light, or an adaptor used. The latter are almost impossible to find, as they've not seen significant use in decades, but can be made from a plug, socket and flex.
2A plugs look nicer than 5A imho. 2A gives a power limit of 480w per plug.
If necessary, the cost of a professional rewire may be trimmed by the house owner cutting all the chases and routing all the cable as pencilled in by the electrician. Or DIYing the job can make a major saving. News:uk.d-i-y can help explain things, and avoid common design mistakes. Its fair to say though that there are some folk that should not do it themselves.
Cost of Rewiring when Buying a House
Channelling for wiring causes considerable damage and mess, and requires redecoration. Don't forget to cost this in when buying a house.
Listed & Character Buildings
The damage caused by rewiring can sometimes be a real problem in listed, period & other character buildings. In these it is important not to damage or destroy features. In such situations it may be wise to use a written agreement regarding wire routing and damage with your installer. With listed buildings it may be wise to explain to your installer that damaging certain features would be a criminal offence, and that the installation may be inspected. If in doubt about rewiring a listed building, consult your CO (conservation officer) first. Ignoring the issue can land you with the cost of correctiion works later.
When it is desirable to keep period electrical features, this can be done legally and safely, but it is not as simple as just connecting them up, and its specialist work. There are a few ways to do it, but this is a subject for another article.
CFL Light Quality
CFL energy saving bulbs are available in a wide range of qualities. Some produce excellent quality light, copying filament bulbs faithfully, and are very long lived, some produce a pinkish so-so quality light, and some are simply unacceptable (sometimes with CCT of 6000K or more). This variation has led to a reputation for substandard light quality. The easiest way is to try different brands to see what's good, trying one of each initially.
The other pitfall to avoid with CFLs is the misleading wattage equivalences quoted on the packs. Real power equivalence ratio is 3-4x, so one can ignore the pack claims and use at least 15-18w to replace 60w, and 25w to replace 100w.
Futureproof Fitting Choices
Lighting is likely to change over the course of the installation's life. Filament bulbs may be banned, and either filament or CFL may yet fall out of favour for domestic lighting. And LEDs might reach the point where they become the prime choice for a lot of domestic lighting.
Picking light fittings that can take either GLS or CFL helps avoid problems later. That way there will be no need to replace light fittings, whatever the future may bring. CFLs are generally larger, and not all fittings can accommodate them.
R80 spotlight fittings are not ideal: although available in CFL form, many R80 CFLs are very expensive at over Â£20 a bulb. There are also Â£6-8 ones available, but these have lower light output, and in some cases other issues too.
ES (screw in) bulbs generally cost more than BC (Bayonet cap) bulbs, and ES are prone to jams and breakages, and very rarely, bulbs falling out. ES sockets have rarely killed people, whereas BC haven't so far. So BC has all the advantages.
Low power miniature base bulbs (SES, SBC, E14 etc) are generally higher priced than ES and BC, are not always as widely available, and require the stocking of more bulb types. So these are best only used when there is a reason for them.
SES and SBC lampholders must not be used on circuits >6A, so some people recommend not using 10A lighting circuits in dwellings, as an unskilled person might fit an SBS or SBC decorative fitting at a later date. 6A mcbs with 1.5mm^2 cable (rated for >10A) gives the best of all options.
A good house lighting design will use a small variety of bulbs, making stock keeping easy. All will be easily obtained and easily stored bulb types. Ideally they will also all be low cost high efficiency types.
Ideally the following types will not be used:
- Tubular filament bulbs - very poor energy efficiency, safety issues
- PAR38s - some of the most expensive domestic filament lamps available, and with very little advantage over R80 and R90.
- fluorescent tubes in large sizes (5', 8') - awkward to store, produce too much light in one place for most domestic uses
- fluorescent tubes in relatively uncommon sizes (6', 3') - harder to find the wanted tube type.
5' tubes are however useful for garage and workshop lighting, and spares can be stored there.
All fittings should be readily accessible so that relamping is easy and safe. The temporary loss of one light should not cause any safety problem or inconvenience.
Outdoor Security Lighting
A common mistake is to use a 500w halogen when 100w or 150w would be more appropriate. Blinding burglars does not seem to make them see the light.
Placing your PIR light directly above the door rather than away from it means the visitor's face is lit, yours is not, and you're not looking towards a light bulb, but they are. This maximises your security on all 4 points.
If the door is a short distance from the pavement in town, a PIR detector with a short range can avoid unnecessary repetitive triggering. If the door opens direct onto the pavement, but is set back a foot or more, an infrared beam-break trigger may be the only way to avoid frequent false alarms, and uses much less energy than an always on light. These are not popular today, but may be obtained from security suppliers. If you have a porch that opens onto a pavement, putting a PIR high up inside the porch on the small sction of wall at the front can shield the pavement from its view.
Ideally position PIR sensors so they dont gaze at the sun, they don't look at lights they control, and approaching visitors walk across their field of view. If you don't meet these recommendations they will usually work, but sometimes performance problems can occur. If your situation means you have to ignore all 3 recommendations, it may work fine, but don't blame the manufacturer if it doesn't behave perfectly.
Finally, don't forget to set the adjustments on a PIR once its installed. Sensitivity adjustment determines how close someone has to be before it triggers, and dawn/dusk adjustment determines at what daylight level it stops switching on. Its a little optimistic to expect all units to come correctly pre-adjusted.
Tree & Shrub Lighting
Lights among clumps of bushes or up trees can be pretty, but the wiring is more expensive than putting it on the wall, and has more chance of failure. Halogen capsules should not be fitted near foliage, as halogen capsules run at very high temperatures and are a fire risk. Outdoor wire runs should be on their own circuit, with their own fuse or mcb & RCD. The reason for this is failure rates are higher than with indoor wiring, and wiring them onto existing indoor circuits can therefore cause unnecessary trouble and expense.
CFLs are generally ill suited to PIR use, but well suited to lights that stay on. When using CFLs outdoors, the type with their own built in glass/polycarbonate cover is preferred, as these are better able to maintain sufficient temperature to keep light output up, and are to some extent more robust.
CFLs used outdoors in very cold weather will light at reduced brightness and be slow to warm up. Some CFLs are better suited to outdoor use than others. Use CFLs specified for outdoor use, or maybe just try a few and use the ones that work ok in cold weather.
Outdoor wiring should be on its own RCBO (or RCD), since the failure rate of outdoor wiring is much higher than indoor wiring. If both were on the same RCD, RCBO, MCB or fuse, failure of the outdoor wiring would also cause failure of the indoor circuit to which it was connected.
Making Outdoor Lighting Look Good
2 or 3x 40w & 60w lights tend to look much better than one 100 or 150 watter. Lights among foliage look much nicer than bare lights. These 2 simple tips make the difference between bare & functional and pretty lighting.
Outdoor Light Fitting Corrosion
When picking outdoor lights, beware of cast aluminium lights with steel cover fixing screws, as the cover screws are likely to corrode solid. If cast ali fittings are used, use another way to secure the lids on if you want them to last. Wire ties or plastic screws are usually workable options.
Is your electrician competent? Many are, but there are certainly some that aren't. If you wish you can ask them a question or two and check the answers. This also has the benefit of politely letting any cowboys know you might check on their work, which will be offputting to some. An example question might be: What earthing system will I get?
Low Voltage Wiring
There are several reasons to incorporate low voltage wires when rewiring. Increasing use of internet and computer networking, electronic security, more efficient and comfortable separately zoned heating control, the convenience of phone sockets in any room you want them, hifi distribution, all these can be accomodated by incorporating LV wiring into the house. Cat 5e is currently the best option for computer connectivity. No doubt this will change in future, but 5e is the existing standard expected to remain in use the longest, mainly due to its widespread use. Cat5e is also good for phone extensions (which may pass broadband signals now or in future). Either multicore burglar alarm cable or cat5e can also be used for security, door bell, intercom, Lv heating control, baby monitoring, backup lighting, fire detector interconnection, and who knows what other apps will become popular in future.
A 100m reel of multicore LV cable is very cheap at around Â£10, so some people are now incorporating this wiring when they rewire. If choosing between multicore (alarm cable) and cat5e, 5e has more potential uses and can carry faster data, so is the better option.
While cable cost for LV wiring is cheap, the labour required is not so cheap. Ways to cut costs down are discussed in the main article, Low Voltage Wiring.
Built in nightlighting reduces night time accidents and avoids dazzle. 3w CFLs are effective. A lampholder can be fitted in most rooms, or less conveniently plug in lights may be used.
Fear of the Dark
For small children, a 3w CFL bathroom light left on can make life easier for them. This can be fitted either as a separate fitting, or a bathroom globe type light taking 2 bulbs can be used with a twin wall switch. This is a lot less unpleasant for grownups in the night as well. Run cost if left on 24/7 is about Â£2.50 per year.
Flush or surface mount
Electrical accessories are usually recessed into the wall so they sit nearly flush. This looks better and avoids them being a problem with placement of furniture.
Surface mounted wiring and accessories are a cheaper option, but in most cases don't look particularly good.
This choice is simple, but if you didn't know what you wanted you could end up with the cheap option without realising what was being agreed.
Bare Stone walls
Exposed stone walls are difficult to wire in a way that looks good.
- Copper MICC (Mineral-insulated copper-clad) cable can be run low on the wall and left to oxidise and turn a dull colour. This is the best of the straightforward options.
- PVC cable can be painted to stand out less. Someone with basic art skills could even camouflage it.
- Burying the wiring in the mortar between 2 layers of stone is a more extreme option. This will often mean using a metal sheathed wire, which will take work to shoehorn into an uneven line.
- Low voltage light fittings can be fed from 2 cores of enamelled copper wire, which is by far the least visible of all wire types. This can be surface mounted without it being noticeable. It can also be buried under the surface or run in cracks and gaps. 12v CFLs, filament lamps and halogens are all available. To use mains light fittings at low voltage, the bulbholders in them need to be replaced.
- Flush floor mounted sockets can sometimes be used to eliminate wiring on the wall.
- Wiring can be run in modified wooden skirting board incorporating sheet steel between wood and cable.
- If you're brave you can make a feature out of wiring. This is difficult to make work aesthetically, but it has been achieved at times. Halogen spots clipped onto 2 thick steel cables is a now classic example of this.
Get it in writing
Unless you just want 'whatever,' is best to get any features you specifically want in writing. Otherwise you may find what you get is not what you agreed on or paid for.
You and only you are responsible for your actions. There's no point blaming me or us later if you did something not addressed by this, or misunderstood and mis-implemented, acted on an error or omission, or followed this advice and got unsatisfactory results. This writing is not intended to replace the advice of a skilled electrician that has seen your house and discussed your specific requirements, and can only be general and limited in nature. It will however enable many people to get significantly better installations and avoid some common causes of accidents and unnecessary trouble & expense.