My Complete DIY Rewire

Hello Friends!

Disclaimer: I realise I'm probably putting myself up for receiving a bit of flack for undertaking a complete rewire whilst asking what some of you might deem to be stupid questions. All I can say is I haven't got a choice, I'd like to do this as safely as possible, hence coming here to ask for and gratefully receiving your help. Please treat me as if I haven’t got a choice and that I’m doing the best with what I’ve got rather than that I’m making a stupid decision.

Background: We bought an old house with pre-existing shockingly bad DIY electrics. The walls have no cavities, the floors/ceilings have no cavities, some of the ceilings have wooden beams. (“Character property” they called it)

I’ve designed a new wiring layout which I think will leave very few exposed/visible wires, and so far in studying BS7671:2008 will comply with regulations. I’ve done a 3D model in Sketchup. I’ve also read up and am complying with Part P of the building regulations for a DIY electrical installer.

The basics of the design is that I’m taking all of the cables up into the loft and then dropping down two floors. This means sockets at the front of the house in the bedroom and sockets directly below in the lounge room will be on the same circuit, and likewise sockets at the back of the house in both lounge and bedroom will be on a separate circuit/fuse.

I’ve bought a Makita chasing tool with a 3kw vacuum - on a test chase it’s doing an extremely good job of removing dust and cutting nice clean chases. So dust won’t be a concern.

I have a few initial questions:


What is the recommended maximum total length of a 2.5mm ring main circuit? Likewise for a 1.5mm lighting circuit. I’ve found it difficult to pin down a figure but it looks to be around 78-80m?


Am I ok to have sockets on different floors on the same fuse/circuit?


Am I ok to have sockets in one room on two different circuits?

I do plan to create a zone diagram for in the CU which very clearly shows which sockets/lights are on which circuits.

The final step will be to have a professional electrician install a new consumer unit and test my work.

Thank you all for your time and your help.

Andy

Yes you can split side to side or front to back in fact it is often considered better as the earth loop impedance is often lower doing it that way.

Yes you can have two circuits in one room. It is only when using 3 phase when this becomes a problem.

It is considered with a ring final 106 meters is the limit. If you go to my page and click calculate you will see how the figures are arrived at. For a lighting 6A radial using 1.5 mm² you will see it's around 44 meters.

I would not go to the edge as it's a real pain if once complete and doing your earth loop impedance tests it does not comply.

You will need to put in the figures for your own house. The 0.35Ω Ze is the maximum for a TN-C-S supply but a TN-S is allowed 0.8Ω and a TT 200Ω the calculator was only designed for a TN-C-S supply so with any other supply you need to start from scratch.

PreferNotToDieOrBurn said:

The final step will be to have a professional electrician install a new consumer unit and test my work.

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In all of your planning you have forgotten that this will be your first step, not the last.

Electricians who are members of the Competent Person Scheme are permitted to notify works that they have done themselves. They just cannot do the final connectand test, unless they lie on all of the documentation.

You have two choices under the current LAW.

1. Find yourself a registered electrician. There is a website with them all on
http://www.electricalcompetentperson.co.uk
Find one who will let you do most of the grunt work, but what cables etc you install will need to be under his direction. He/she could then carry out the final testing, certification and notification to the local authority.

2. Raise a building notice with your local authority and state that you are doing your own electrics. The LABC will want to inspect the work at various stages and will expect you to be able to design, install and test the work to BS7671. So yopu'll need to bone up on that - that document has all of the answers re max sizes for radial and ring circuits. and everything else - its a fascinating read.

There's more info on your options at //www.diynot.com/wiki/Electrics:part_p:DIY-Electrical-Work-and-the-Law

I dunno if i'm correct but how about:

1) Putting the CU upstairs somewhere. Would that not be more sensible if you saying most/all cables are going up ?

You would need a switch fuse by your incoming supply and appropriate cable to the cu.

2) Using radials for sockets (excluding kitchen, or use 4/6mm radial for kitchen)

There is a huge difference between working on a vacant house and one where one is still living in it.

With a vacant house likely new consumer unit would be last item but with a occupied house likely the first.

I realise you could ask an electrician to fit a consumer unit with an array of sockets one on each outlet so that all wiring would then be an extension from an existing circuit so then only bathroom would need doing by a scheme member. However in real terms I would assume you want to live in a safe house so methods of getting around the law are rather silly and pointless as then any errors are totally down to you.

So hurdle one is the LABC and getting them to allow you to start. In the beginning there was a fee fixed on the price of the job starting at £2000 and most re-wires fell into that first group. And the LABC was not permitted to charge for testing.

However the rules changed and if the LABC select to use a sub contractor to inspect and test that cost can be passed to you. Much depends on your local inspector but waiting for an inspection can really be a pain. There is a time limit I think 2 weeks but it means instead of doing one chase at a time you are forced to wire all rooms together to reduce costs. So every room will have chases down the walls together.

If however the LABC will accept your testing and inspection and will just verify the results then your looking at some thing very different you can do a room at a time and when complete you submit test results and within two weeks you get your completion certificate.

As an electrician when I did some wiring I tested and inspected and submitted my results and got the completion certificate. Your first hurdle is to get the LABC to allow you to inspect your own work.

You can of course do a bit at a time but every visit by a sub contractor to test and inspect you pay for. Very quickly your paying the council more to over see your work than it would cost to get some one to do all the work for you.

Although in theroy you can DIY legally in practice unless you have some written qualifications you can show the LABC then DIY costs more than getting the job done for you.

I think the councils had a major problem with Part P one their staff were not trained and two DIY people get it wrong so a re-wire becomes a multi-re-wire with do it again and do it properly. Inspectors could have to return to site many times where people got it wrong so the law change allowed charging for each inspection.

If I was to do it now I would wire bathroom and change consumer unit and put one item on every RCBO first after that it does not need further inspection by LABC but I am confident I will not make any errors I will not find when doing my own inspection and testing. If I want to sell the house after I would get some one else to do the EICR so any errors are not directly down to me. Mainly as I don't have public liability insurance so would want some one with insurance to take the rap if there are any faults.

We all think we can do it right. The Emma Shaw case shows even when the electrician does all the work correctly it is the final inspection and testing which is all important. The electrician left some slack cable as to why we don't know. Other than that everything he did was correct. The boss asked a semi-skilled to do tests which should have been straight forward he was after all only transferring what the meter showed onto a bit of paper. The main error was the plaster who damaged the cable but it was the electrical boss who carried the can. He didn't even visit the site. It would of course be the same with the LABC if you or any other trade make an error and as a result some thing like the Emma Shaw case happens then the inspector is looking at a prison sentence. Any wonder why they use third party inspectors.

Good luck be be aware of what you are taking on.

PreferNotToDieOrBurn said:

This means sockets at the front of the house in the bedroom and sockets directly below in the lounge room

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That sounds incredibly limiting in terms of placing sockets where you want them

Taylortwocities said:

PreferNotToDieOrBurn said:

The final step will be to have a professional electrician install a new consumer unit and test my work.

Click to expand...

In all of your planning you have forgotten that this will be your first step, not the last.

2. Raise a building notice with your local authority and state that you are doing your own electrics. The LABC will want to inspect the work at various stages and will expect you to be able to design, install and test the work to BS7671.

Click to expand...

Thank you.

Regarding the first point, the existing electrics are staying as-is until the new wiring is completed. It's all surface wiring and I don't need to disturb it to stick the new wiring in (partly designed it to accommodate this)

Option 2. is the route I'm going down. It's actually quite a good deal for a DIY'er because the costs of inspection and testing are carried by the local authority.

OwainDIYer said:

PreferNotToDieOrBurn said:

This means sockets at the front of the house in the bedroom and sockets directly below in the lounge room

Click to expand...

That sounds incredibly limiting in terms of placing sockets where you want them

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It might sound that way but it actually works out quite well.

ericmark said:

I think the councils had a major problem with Part P one their staff were not trained and two DIY people get it wrong so a re-wire becomes a multi-re-wire with do it again and do it properly. Inspectors could have to return to site many times where people got it wrong so the law change allowed charging for each inspection.

Click to expand...

This is news to me, and a potential major issue for us. Bummer, I'll need to re-research how this works. Thank you for your comprehensive reply! I'm not looking to skirt the law, and I am looking to do this safely.

PreferNotToDieOrBurn said:

ericmark said:

I think the councils had a major problem with Part P one their staff were not trained and two DIY people get it wrong so a re-wire becomes a multi-re-wire with do it again and do it properly. Inspectors could have to return to site many times where people got it wrong so the law change allowed charging for each inspection.

Click to expand...

This is news to me, and a potential major issue for us. Bummer, I'll need to re-research how this works. Thank you for your comprehensive reply! I'm not looking to skirt the law, and I am looking to do this safely.

Click to expand...

As I understand the situation, they cannot charge extra (over and above the notification fee) for activities of their own inspectors. However, many/most LABCs do not have (any or enough) appropriate inspectors for electrical work and therefore contract out that work to outside electricians. As eric has said, although I believe that the rules didn't initially allow it, I also believe the rules were fairly quickly changed so as to allow the LABC to 'pass through' the cost of these contracted outside electricians to the applicant.

Kind Regards, John

Thanks John, might be worth a discussion with the authority and get confirmation one way or the other.

Another few questions:

I'm thinking of using a glue gun or something like no-more nails to fix the cables within the chases - Are there any drawbacks with doing it this way? (Other than not being able to remove the cables, but I'm not putting them in conduit anyway)

If I'm installing wiring in open chases "as decoration" but not connecting them to a CU, can I delay the notification until my intention changes and I decide my decorations would better serve as new electrical wiring? I know I'm pushing the limits here but I can't get the wiring done in 2 weeks (let alone 2 months, as only working a couple hours each weekend) and I'd prefer it all to be inspected/signed off in one shot. What I'm thinking is that cables laid in chases aren't technically an electrical circuit until they are connected and could literally just be decoration (although god awful decoration). Also if I leave it all open could/would a friendly electrician be happy to/able to come in and check it out/sign it off as their work? I do know a few friendly leccys.

PreferNotToDieOrBurn said:

I'm thinking of using a glue gun or something like no-more nails to fix the cables within the chases.

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Hot glue is likely to cause damage to the insulation. Gripfill and the like could be used and will be substantially cheaper than hot glue. I use this: http://www.toolstation.com/shop/p10243

PreferNotToDieOrBurn said:

If I'm installing wiring in open chases "as decoration" but not connecting them to a CU, can I delay the notification until my intention changes and I decide my decorations would better serve as new electrical wiring?

Click to expand...

No. You notify before anything is started. During that process you must also ask them what inspections etc. they will want to do, when, how often, etc.

PreferNotToDieOrBurn said:

I know I'm pushing the limits here but I can't get the wiring done in 2 weeks (let alone 2 months

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There is no 2 week limit.
Building notices expire after 3 years if the work has not started.

PreferNotToDieOrBurn said:

Also if I leave it all open could/would a friendly electrician be happy to/able to come in and check it out/sign it off as their work?

Click to expand...

Unlikely. If you want an electrician involved, contact them before doing anything.

ericmark said:

For a lighting 6A radial using 1.5 mm² you will see it's around 44 meters.

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It looks like I've got over 44m, presumably simply sticking in 2.5mm should do the trick?

The more I read, the more I'm convinced that you are not yet competent to be tackling a complete rewire.

you wouldn't want to use 2.5mm for lighting as its a nightmare to get into the accessories