Rewiring Tips

This article will need a fair amount of editing and formatting. However its a good start, with lots of useful information for anyone about to rewire.

Introduction

The basic electrical installation design is fairly much decided by the 16th edition regs, so unless you get into specialist unusual or illegal territory, most 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 lot of difference.

The Basic System

You'll get 30A rings supplying the sockets, or occasionally 20A radials. You'll get 6A lighting circuits, or occasoinally 10A. Youll get dedicated feed for cooker and shower if you've got those, or the oven might end up on a 13A plug these days. You'll usually get 1 or 2 RCDs, which if installed poorly can sometimes produce endless frustration by taking out the power on a frequent basis.

Glossary

MCB: an overcurrent trip found in the consumer unit, aka fusebox. This replaces a fuse. (Fuse wires can still be legally installed.) Contrary to popular myth, MCBs are not a safety benefit for general use. Where householders can be expected to be irresponsible, eg rented property, mcbs are preferred to rewirable fuses, which can be abused.

RCD: earth leakage trip found in the consumer unit, aka fusebox. This will trip if earth leakage current is too high. Unfortunately theyre well known for nuisance trips. The majority of older installs have no RCD.

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 rewire the power can stay on.

TT: an installation using a local earth rod. TT installs must have a whole install 100mA delayed RCD, since an earth rod alone is inadequate to clear faults. But these whole system RCDs should be avoided with other installation types, as theyre a known source of problems.

The Choices

Now some ideal choices which will add a bit to installation cost, but are worth it if you've got the £100.

Split Load CU:

Use of a split load CU means that whatever may happens with your electrical system, you dont need to turn it all off. One half can be turned off while the other is on. 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, just check that you're getting one. Typical extra cost: £0

RCDs

RCDs are almost universal in new installs. Unfortunately theyre also a source of a great deal of trouble for a minority of householders.

What you dont want is the default install of one 30mA RCD covering half or even the whole house. Most of these work ok, but some create no end of frustration and expense for the householder. For £35-£100 more you can have 2 or 3 RCBOs instead of one RCD, which eliminates most RCD nuisance trips, and minimises the consequences of any that do occur. This way if an RCBO trips, you lose only one socket circuit instead of all power.

A freezer is best put on its own dedicated feed, so other appliance faults dont stop it working and ruin £££ of food and a couple of days of your cooking efforts. Dont have any RCD on the freezer supply when possible. This means that to meet 16th edn regs, the socket for the freezer should not be likely to be used by outdoor tools, so dont put the socket by the back door.

Unless you have a TT earthing system, lighting should not be on an RCD. Lighting circuits are not an electrocution risk. RCDs 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 such setups have been encountered.

Sockets

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). Doubles are enough if you sprinkle them around the room, and dont mind using many 4 & 6 way extension leads.

Halogen Lighting

I dont recommend halogen downlighters. 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 halogen downlighters penetrate the ceiling plasterboard fire and smoke barrier.

Its wise to calculate run costs before installing halogen, to avoid regret. As an example, 500w of halo downlighters on 6 hours a day would cost £65 per year per room in electricity, plus 12-24 bulb replacements per year at £1 each, making a total cost of £77 per room per year. 4 rooms of halogens would equal £308 per year, or £9000 per 30 year product life. For some people thats fine, but for some its not the best way to spend that money.

For those tempted by halogen, I would suggest using lower power halogen downlighters, eg 10w or 20w, and making up the rest of the light level with better light sources, such as uplighting or concealed lighting.

Avoid mains voltage halogens below 150w. Mains bulbs are lower efficiency compared to low voltage, more fragile, shorter lived, and more susceptible to early failures. They're also more cost per bulb.

Switchbanks

Use switchbanks where possible. These are 2 or more switches in the one box, where one would traditionally find one. Each switch controls some of the lighting. Thus it is easy to control lighting brightness. Cost about £1 per switch point more when new, they typically save this much in under a year. The easy ability to adjust brightness significantly improves both living comfort and utility, saves energy, and reduces cost of energy and hassle of replacement bulbs.

Using dimmers to achieve a similar result causes much greater electricity use.

Uplighters

If you want uplighting, which is often a good approach, use spotlight fittings for this with ordinary GLS bulbs in, or CFLs (not spotlight bulbs). The fittings need to shroud the bulb of course.

Dont use those 'orrid plaster uplighters, theyre inappropriate for uplighting. They create a high intensity light patch, which uplighting is intended to avoid, and light the wall from such a shallow angle as to magnify even the tiniest blemish into a mess.

Avoid halogen uplighters, which are a fire risk.

Kitchen worktop lighting

Mini fluorescent strips are a good idea, but are sometimes supplied with 4000K bulbs, which really dont look good. Fluorescent tubes come in a wide range of different whites, usually named either by colour temperature in K, or by long established names such as warm white, daylight, cool white, etc.

Fluorescent tube types

Use 2700K, 3000K, or 3500K white tubes if you like, but I dont recommend higher colour temperature tubes. 2700K is the colour of GLS filament bulbs, it matches perfectly with traditional filament bulbs, which are a slightly yellowy white. 3000K is the colour of halogen bulbs, cleaner and crisper than 2700K. 3500K will not match other light sources, unless theyre also 3500K fluorescent, but used alone they give a clean and slightly cool look. 4000K just look bad, and 4500K are like the old fashioned cool white tubes that gave fluorescent lighting such a grim reputation.

Fluorescent fittings

Fluorescent lighting can look good if chosen and installed well. Unfortunately the all too common choice of a bare bulbed butt ugly fitting in the centre of the room with a tube chosen at random is not a recipe for pleasant lighting. Good fluorescent lighting needs the following points:

Filament Strip Lights

Do not install filament strip lights. Filament strip bulbs are around a foot long, and rated 30w and 60w. These are very cheap to buy but have particularly poor energy efficiency, unnecessarily high run cost, and the bulbs need frequent replacement. They were popular before WW2, and should have been left there. Flourescent strips will have much lower power ratings, since theyre several times more efficient.

Some halogen worktop lighting arrangements cause glare.

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 each year, plus fatalities. Do not install stair lights out of reach, this is a recipe for a serious accident as well as most inconvenient, and a common poor design choice in times past.

Interior 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 £17 each.

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 lower with a type C MCB. MCBs cost about £6 each.

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 legal complications these will usually be round pin sockets.

You can either fit a round pin plug on the light or use a round to square pin adaptor. The latter are difficult to find used, as have not seen significant use in decades, but can be made from a plug, socket and flex.

Cutting costs: If necessary, the cost of a professional rewire may be trimmed by the house owner routing all the wire as pencilled in by the electrician. For more serious savings, do it yourself. News:uk.d-i-y can help explain things, and avoid common design mistakes. Its fair to say there are a few folk that should not do it themselves.

Dont overlook the fact that channelling wiring causes considerable damage and mess, and requires redecoration. Dont forget to cost this in when buying a house. This can sometimes be a real problem in listed and period buildings, where it is important not to damage or destroy features. In such situations it may be wise to consider 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 could constitute a criminal offence.

CFL energy saving bulbs are available in a wide range of qualities. Some produce excellant quality light, copying filament bulbs faithfully, and are very long lived, some produce a pinkish so-so quality light, and some are simply unacceptable (often 6000K or more, and found in pound shops). This variation has led to a reputation for unsatisfactory light quality. Try different brands to see whats good, trying one of each initially. The other pitfall to avoid with CFLs is the misleading wattage equivalances quoted on the packs. Real power equivalence ratio is at best 4x, so ignore the pack claims and use 15-18w to replace 60w, and 25w to replace 100w.

Pick light fittings that will take either GLS or CFL. That way there will be no need to replace light fittings whatever the future may bring. CFLs are generally larger, and not all fittings will accomodate them. R80 spotlight fittings are not ideal: although avavilable in CFL form, these CFLs are very expensive at over £20 a bulb. There are also £8 ones available, but these have lower light output, and are a bit larger, making the fitting look like the bulb is falling out as well as dim.

ES screw in bulbs generally cost more than BC Bayonet bulbs, and ES suffer jams and breakages, and very rarely, bulbs falling out, so BC is generally preferred.

Low power miniature base bulbs (SES, SBC, E14 etc) are higher priced and lower efficiency than ES and BC, and not always as widely available, so are best only used when there is a good reason.

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. All fittings will be readily accessible so that relamping is easy and safe. The temporary loss of one light will not cause any real problem. Tubular filament bulbs, PAR38s and 8' fluorescent tubes will not be used. Switchbanks will be used rather than dimmers. Most lights will be able to accomodate either a filament or a CFL bulb.

Outdoor security lights: the most common mistake is to use 500w halogens when 150w or less would be more appropriate. Lights among clumps of bushes or up trees can be pretty, but the wiring is more expensive, and not always long lived. SWA cable should be used in preferance to MICC, as MICC tends to fail outdoors from water ingress. 2 or 3x 40w & 60w lights tend to look much better than one 100 or 150 watter. When picking outdoor lights, beware of cast aluminium lights with steel cover fixing screws, as the cover screws rapidly corrode solid. If cast ali fittings are wanted, look for another way to secure the lids on if you want them to stay. Wire ties and plastic screws are options.

Is your electrician competent? Many are, but some arent. If you wish you can ask them a question or 2 and check the answers. This also has the benefit of acting as a warning to any cowboys, letting them know you might check on their work. An example question might be: What earthing system will I get?

There are several reasons to incorporate low voltage wires in the walls 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. A 100m reel of multicore LV cable is very cheap at around £10, so many are now incorporating this wiring when they rewire. Cat 5e is currently the best option for computer connectivity. No doubt this will change in future, but 5e is the standard expected to remain in use the longest, mainly due to its widespread use. Cheap multicore burglar alarm cable or cat5e can also be used for security, phone, door bell, intercom, Lv heating control, baby monitoring, backup lighting, fire detector interconnection, and who knows what other apps will become popular in future.

You and only you are responsible for your actions. Theres no point blaming me later if you did something not addressed by this, or misunderstood and misimplemented, or acted on an error or omission. This writing is not intended to replace the advice of a skilled electrician that has seen your house and discussed your rquirements, and can only be general and limited in nature. It will however enable many people to get significantly better installations and avoid common causes of accidents.

Its still legal to install round pin sockets btw.