How to tackle partial rewire and complete kitchen replacement

Hello
We have a 1960s house that needs:
A new consumer unit to replace the old fusebox and possibly some other electrical work
A new kitchen floor (once the woodworm underneath has been dealt with). A repaired and skimmed kitchen ceiling. A completely refitted kitchen to include moving the gas hob across the kitchen. A Partially rewired kitchen with separate unprotected circuit for freezer?
The kitchen will have to be stripped out before the work can be done and we do not wish to be without the kitchen for months while different contractors get around to doing their bits and I DIY some.
Looks like we will have to
a) get a specialist firm to do the woodworm.
b) bite the bullet and use a firm that can undertake all the kitchen work.
c) get a separate electrical contractor to do the consumer unit and any other necessary work.
1) Any comments on how to tackle it? Consumer unit etc or kitchen rewire first?
2) When the consumer unit is replaced and the kitchen is rewired just how much of the other wiring has to be checked? Lighting circuits do have earths and the sockets are rings with the odd spur. Have noticed the gas supply is not earthed.
Thanks in anticipation. I have refitted a couple of kitchens over the years but this is a bit more than I want to tackle.
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Invisible Man coughed up some electrons that declared:

Not a professional electrician, so this free advice is worth what you've paid for it ;->
I would go for the CU change first. Here's why I think that:
BTW - Do you know when the last re-wire of the house was carried out?
With the extra provisions of the IEE wiring regs (17th), you will probably need most if not all of the final circuits protected by 30mA (or less) RCDs.
Circuits in special locations (eg bathroom, shower room), 30mA RCDs are mandatory on all circuits. All 13A socket circuits (including cooker circuits where the cooker switch has a socket) need a 30mA RCDs too. The rest of the circuits will generally need RCD protection due to the cables not being buried > 50mm deep in the walls/ceilings or having other mechanical protection.
In short, a lot of electricians won't be happy to wire new/replacement circuits like your kitchen to a non compliant old board.
So new CU first is probably easier. CU would need either 2 (or more) RCDs in a split configuration (so called "17th Edition boards") an RCBO per circuit (MCB+RCD in one unit) as the two most common solutions.
You *can* have your non-RCD circuit from the fridge or freezer, but the socket should be marked accordingly *and* the cable must be either run on the surface OR mechanically protected (MICC or SWA armoured or in earthed steel conduit) OR buried >50mm under the surface (often impossible) OR earth-foil-screened to a certain BS (which I can look up if you ask), eg FlexiShield or XL-Shield cable.

That's an area of some debate. Some electricians will insist all circuits comply with the 17th. Some will feel able to justify only the circuits they've altered or replaced being 17th, and note the others as limitations ie OK to an older edition of the regs). But I would expect them to test all the circuits regardless and rectify any faults. In theiry, they should complete an EIC (Electrical Installation Certificate) after changing the CU and this needs test figures from all circuits.
Hopefully you shouldn't expect to have any major problems unless your wiring is actually the original 60's stuff, in which case it might be getting past its prime - lack of earthing on lighting circuits is the biggest pain, but you have this. Obviously, only the person looking at your wiring can pass the final judgement.
If the electrician does the CU change thoroughly, they'll be looking for (major items, not complete list):
1) CPCs (earths) on all circuits with proven continuity to all outlets and switches.
2) Live-Earth loop resistance to be low enough on each circuit to comply with the choice of breaker/fuse protecting that circuit.
3) General polarity correctness (live goes to live terminals etc).
4) Main earth bonding correct (eg your gas and water pipes plus oil pipes, structural steel etc if you have any). Also any supplimentary bonding as required.
5) Insulation resistance checks L-N, N-E and L-E to be greater than 1 megohm at 500V test per circuit (hopefully much much higher, like 100's megohms).
=== Item 2 above can be sometimes fail due to loose terminals. If the failure is marginal, one can skirt the issue with a lower breaker rating or RCBO depending on the severity and other informed judgements.
3 is usually fixable (swap the wires where they're wrong)
4 - this will be the first thing that must be fixed. But it's generally a trivial job involving suitable green/yellow wire and some clamps to the right places.
5 - if this fails, you've got problems that may need a re-wire of the affected circuit, unless the problem can be isolated to a faulty accessory.
You *might* find an electrician who is happy to be less rigorous, but it's not so bad if you look on it as a good opportunity to have the whole system health-checked, then you can rest easy knowing the whole system is safe.

Yeah - I feel the same way about my house renovation. Been compensating b y planning it to death! :)
Cheers
Tim
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Invisible Man wrote:

New CU first. If you remove or don't have an electric cooker/shower/heating on the old CU, the old CU can then be supplied through a 32A or 45A circuit (with RCD). New wiring can be added to the new CU. The old CU can then be removed when finally not needed.
You can also get the new CU connected to the supply without having to test the wiring, because the old wiring won't be connected at this point. You will connect it later...
Owain
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Invisible Man wrote:

Much easier to do the wiring/gas pipe before the floor & ceiling are done.
--
Dave - The Medway Handyman
www.medwayhandyman.co.uk
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