DIY house rewire

[pcorker]

Hi
This seems to be a busy and helpful forum!
As a DIYer who rewired a house about 25 years ago (...it's still standing ) I believe that I am still allowed to rewire my present house but that the LABC must be notified first and they will need to arrange inspecting, testing and certifying it.
The only bit I am not allowed to do would be connecting the CU to the supply.
I intend installing a basic new system completly separate from the old system which will become redundant on completion.

Question 1. Am I correct in this belief?
Question 2. I presume that they will want to inspect before and after plastering in and with floorboards open etc.
I need to keep to the IEE Edition 16 wiring regs. I have read Brian Scaddan's guide but it was not much practical help.
Question 3. Can I lay cables loose in the 13" height ground floorspace? The house is on a concrete raft.
Question 4. Can I lay cables loose onto the upper side of the plaster board ceilings?
Question 5. Can I lay cables loose on top of the mineral wool roll insulation in the (unused) roofspace?
Question 6. Should I just keep it simple and just put every CU circuit (only: 2 power; 2 lighting and one cooker) onto one RCD or should I split it? What do inspectors prefer?
Question 7. Can anyone recommend a book that covers this basic stuff without going into Farady cages and 3-phase etc.? I think I lost my old "How to Rewire Your House" pamphlet!

 

[ColJack]

1. as far as I know yes.. the EAWR and the HSAW only requre that a person be competent... not qualified.. to carry out the work..

you can even do the CU connection yourself, you will need to contact the DNO to come and cut the main fuse tags and then to come back and re-install them later.. you will probably have to have done a complete test of the install prior to them re-fitting the fuse..

if you need the tail extended however, then they will have to do that..

2. yup, from what i've been told they do a first fix inspection ensuring things like routing of cables etc..
then they do a second fix inspection checking things like fittings etc...

3. best to clip to the joists as if it's on the floor and rats get in they like to gnaw at cable for some reason..

4. I'm not entirely sure on this.. if its loose then you don't know where it is and may put a screw through it if you try to hang something from the ceiling, but the same can be said for clipping it... if you miss with a flooring nail or screw, or a ceiling screw when re-boarding then you can damage it that way too.. also makes re-wires a pain as you have to get to all the clips to replace it..

5. yes you can but bear in mind what you will do if you decide to board out the loft... do not put it under the insulation... it de-rates the cable..

6. only sockets that are liable to be used for outdoor equipment, and bathrooms ( IE lighting, shower, shaver socket etc ) NEED to be on an RCD ( and the bathroom light is just future proofing for 17th edition regs..)
I would install 2 extra circuits, both in the kitchen.. one for the general use, and one radial, not on the RCD for the fridge.. ( stops nuisance tripping defrosting all your food while on holiday etc.. )

Cookers are best not on the RCD as when they get older they tend to trip the RCD for no good reason.. just make sure the cooker switch is the type without a socket on it or it will need to be on the RCD.

7. the "on site guide" is good..

 

[JohnD]

(6) Five circuits is not many... if you are going to the trouble of rewiring, have an upstairs sockets ring, a downstairs sockets ring, and a ring (or radial if it is very small) for the kitchen and/or utility room wherever you have your dishwasher, washing machine and tumble drier. Also have a dedicated non-RCD radial for the freezer (20A in 2.5mm is fine). If the socket is out of the way behind it, OK; but if it is accessible, use an FCU instead of a socket to avoid people plugging hand tools into it.

If you have a larger kitchen, consider putting in two cooker circuits so that you could have a separate double oven and electric hob one day. If it is a large kitchen, put the cooker outlets on opposite walls so you can re-plan the layout in future.

When you are planning the kitchen, allow for vast numbers of double sockets above the worktop. Also have 20A DP switches above the worktop feeding singe unswitched 13A sockets below for your appliances. You can run the circuit all round the kitchen (except for doorways) 150mm above worktop height, this is very economical in labour and materials.

Put plenty of sockets at the same height in workroom, study, garage, workshop

If you have a large garage/workshop and are fond of big power tools, arc welders, paint ovens, smelters etc, give it a dedicated circuit with an RCD inside the workshop where you can easily turn it back on in case of trips.

Allow for a shed or garden supply later.

Allow space in the CU for a future immersion heater or electric shower, and for outdoor lights and sockets later. Buying a large CU is not much extra cost as you are just paying for a plastic box and some fresh air.

Consider using RCBOs instead of a split load; if you have few RCD-protected circuits it may not be much more expensive and can be very much more convenient.

 

[ColJack]

You can run the circuit all round the kitchen (except for doorways) 150mm above worktop height, this is very economical in labour and materials.

I'm assuming you mean from socket to socket in their "safe zone"..?
not just implying that there is a safe zone above the counter for 150mm?

I would put them up higher than that anyway.. under the upper cabinets ( about 50mm down to allow for awkward phone chargers etc that the adapters go up.. )

this reduces the risk of splashing them if you drop a cup of tea or, god forbid, a beer....

 

[securespark]

You can run the circuit all round the kitchen (except for doorways)

Or else you can either limbo under them or high-jump over them!

 

[JohnD]

I'm assuming you mean from socket to socket in their "safe zone"..?
not just implying that there is a safe zone above the counter for 150mm?..

yes, if there are lots of accessories in a horizontal row, the cable run is automatically in its safe zone. It is also very easy to cut into it if you later find you need another outlet (but with sockets and switches alternating, at 600mm intervals, that should be unlikely).

No prob with putting them a bit higher, but should be in clear view, not snuggled up to the underside of wall cabinets.

 

[ColJack]

define "clear view"...

at 6'4", my line of sight under a cabinet is drastically less than my mother who is 5'2"... or even my nephew who is 4'6"...

 

[JohnD]

clear view so you can turn off an appliance in an emergency, e.g. the tumble drier catches fire or the dishwasher floods.

And I think all your family will be able to see mine, at 150mm up

 

[Spark123]

define "clear view"...

at 6'4", my line of sight under a cabinet is drastically less than my mother who is 5'2"... or even my nephew who is 4'6"...

Shorty!!

Nice looking on the top of vending machines lol (there's mostly an inch of dust)

 

[ricicle]

Nice looking on the top of vending machines lol (there's mostly an inch of dust)

Better looking underneath and seeing all that dropped coinage

 

[pcorker]

Thanks for taking the time to reply, guys!

I had just been about to start, having bought a small CU, when I realised that I needed to put in a lot more thought - and to notify! On reflection,and as you point out, I will buy a bigger CU to take the fittings from this one.

I am thinking that soon just about all circuits will need RCD so how about a split box with everything on the RCD split except the freezer which is on the non-RCD side but using an RCBO so it can only be tripped by itself? I suppose that if the lights go out I can use a torch! I'd be prepared to sacrifice convenience for safety.

So I really will have to lift a huge number of floorboards if cables must be clipped to joists - about every 10 inches I think?

Laying loose on top of loft insulation will make THAT job easier.

I had forgotten that safe zones go horizontally as well as vertically. I'll add more sockets in the (unfinished) kitchen as I rip out the old colour wire that I have just put in from my old stock. Wish I had thougt about this better BEFORE I started!

 

[JohnD]

Don't put the lights on an RCD. That is less safe, as they may all go out unexpectedly when you are running downstairs; up a ladder; carrying a heavy object etc.

In the loft I would prefer to see the cables clipped to the side of timbers wherever possible. Then you won't trip over them, or trample them with your great heavy boots.

Lighting cables can go under insulation beceuase they are very lightly loaded. Cables for immersion heaters and electric showers generally can't unless you calculate them and probbaly use twice the size.

 

[ColJack]

I would use 10mm² for shower, and 4-6mm² radial for immersion.. just to future proof..
it won't be long before they start selling 15KW showers probably... ( havent done the calcs.. )

 

[Softus]

it won't be long before they start selling 15KW showers probably... ( havent done the calcs.. )

I recently investigated installing a 12kW shower, for a customer, and the supplier advised against it for anything other than very brief periods or very hot applications.

The supplier said that if you have a normal (body) shower under a 12kW unit then it would be likely to reach its overheat limit and cut out. apparently the typical application for a 12kW unit is hairdressing salons, where they want INSTANT hot water for a quick splash and rinse of hair and/or head.

If they're right about all of that, then 11kW is likely to stay the limit for anything other than Siberian mains water temperatures.

Don't put the lights on an RCD. That is less safe, as they may all go out unexpectedly when you are running downstairs; up a ladder; carrying a heavy object etc.

John, would you tend to put the cooker and IH on the RCD protected side?

 

[securespark]

I would not put the IH on an RCD. The cooker only if there is a socket outlet incorporated in the plate.