Circuit separation

[Rusty2012]

I'm about to do a complete rewire on my house. At the moment the CU is on my dining room wall and I'm moving it to the cupboard under the stairs. It's old school with rewireable fuses and it only has 6 circuits.

I plan on separating them into the following circuits:

Upstairs lights
Downstairs lights
Upstairs sockets
Downstairs sockets
Cooker
Shower
Smoke/heat alarms
Garage

Can I add the following to any of the above circuits or do they need to be separated?
Bathroom extractor fan
Combi boiler
Security/outdoor lighting

Also can anyone reccomend a CU that has a decent amount of space to work in preferably with a couple of spare ways in case I need to add anything later on?

 

[EFLImpudence]

I'm about to do a complete rewire on my house.

You must by law notify the Local Authority Building Control - OR - find an electrician Registered with Third Party Inspection Scheme before you start.

I plan on separating them into the following circuits:

Upstairs lights
Downstairs lights
Upstairs sockets
Downstairs sockets
Cooker
Shower
Smoke/heat alarms
Garage

Ok.

Can I add the following to any of the above circuits or do they need to be separated?
Bathroom extractor fan
Combi boiler
Security/outdoor lighting

It's up to you.
Do you mind if the boiler stops working because of a fault on, for example, a lighting circuit?
The extractor and outside lighting are unimportant.

You may like the smokes/heats on a circuit with, say, the hall light so that you notice when it is not working.

Also can anyone recommend a CU that has a decent amount of space to work in preferably with a couple of spare ways in case I need to add anything later on?

Hager - with two more ways than you need now???

 

[ban-all-sheds]

• For a circuit to supply a given load, how would you go about deciding what cable and protective device to use? (No, you can't just copy what's there because it's going to become your responsibility and what's there might be wrong.)

• Do you know which circuits can be ring finals and which cannot, and what the advantages and disadvantages of each are? (No, you can't just copy what's there because it's going to become your responsibility and what's there might be wrong.)

• How do you calculate maximum demand and how can diversity be used?

• Can you correctly identify all components and connections of a circuit by method of testing or otherwise? In doing so can you identify or recognise anything wrong or dangerous with the circuit? You cannot assume that what's currently installed is OK, and you need to check it before starting work.

• Do you understand how the way in which cables are installed affects how much current they can carry? (No, you can't just copy what's there because it's going to become your responsibility and what's there might be wrong.)

• Where cables need to be joined, how should this be done / not be done and in what circumstances are different methods acceptable?

• Can you identify extraneous conductive parts, and do you know the requirements for main and supplementary bonding of them?

• Which circuits should be RCD protected?

• What about the testing that you should do on your existing installation before you change the CU, if you want to be sure of avoiding grief from new RCDs tripping?

• And what about the tests you should carry out after the installation? What sequence will you do them in and at what point will you energise the installation, and for each test do you know what is being measured, why it is important, how you would carry out the test, and with what equipment, and what sort of results you would expect to get if everything was OK?

• How do you propose to isolate the supply so that you can install the CU?

• Do you believe you are qualified to issue an Electrical Installation Certificate for the replacement?

• Are you aware that you'll need to apply for Building Regulations approval in advance, and as part of that you'll have to say how you'll ensure that your work complies with P1?

 

[oldbutnotdead]

Get someone in to do it. Part P as eloquently explained by others above. Talk to whoever you get in- they may or may not be happy with you doing some of the time consuming crappy bits (chasing walls, running cables) or you may be surprised how cheaply they'll do the whole job for you.

Stuff to think about before your conversation;
GARAGE- is it integral or separate? If separate, do you really want a fault in the garage to take half the house out?
Sockets- considering separating the kitchen/utility room from the rest of the ground floor
While you're making a mess chasing cables in, think about adding coax and data cable runs anywhere they might be useful. Need to maintain 50mm separation between data and power remember.

 

[ban-all-sheds]

Need to maintain 50mm separation between data and power remember.

Not necessarily.

 

[ericmark]

At the moment the CU is on my dining room wall and I'm moving it to the cupboard under the stairs.

I seem to remember that putting the CU under the stairs is no longer permitted. I have not kept up with BS7671:2008 amendments I only have the original, but seem to remember there were a lot of fire protection clauses added to amendment 3, and I seem to remember that includes under stairs locations, it was anywhere else 30 minutes and under stairs it had to protect for 90 minutes. Maybe some one can say if the under stairs was building regulations or wiring regulations I can't remember.

For a whole rewire it is possible that using the LABC route may be cost effective, but it depends who can do the inspecting and testing and if not yourself how many times will it be required. The LABC charge to do the work based on the cost of the job if done by a professional it was £100 plus vat for first £2000 worth of work in Wales, in England it varies council to council. However the rules were changed and now the council can use outside contractors to inspect and test and that cost is on top of the original charge. If it is a case of first fix inspection then second fix and inspection and test that is not so bad, but if you want to use the house while rewiring then it can become very expensive as it requires an inspection and test before any circuit can be used.

If you can convince the LABC that you have the skills to inspect and test then it may be worth while, but unless you can do the whole job, then the cost of getting an electrician to call on a regular basis to test the work done that day would likely be more than getting the electrician to do the work in the first place.

As an industrial electrician with all the qualifications I still intend to employ a scheme member electricians to re-wire my mothers house. I think that says it all.

 

[flameport]

Maybe some one can say if the under stairs was building regulations or wiring regulations I can't remember.

Neither.
The only fire related items added were the nonsense about 'non-combustible' consumer units / cupboards around combustible CUs and the other part about how cables in escape routes are supported.

All the rest such as CUs with metal flapping lids which stay closed, special glands to seal around cables, intumescent seals inside, metal blanks for unused ways and the rest are things which certain manufacturers have invented so they can claim that their products are somehow superior to others and therefore sell more of it.

 

[Taylortwocities]

I seem to remember that putting the CU under the stairs is no longer permitted.

Only for new build properties where the requirements of Part M apply.
Otherwise, the CU needs to be accessible. Whatever you may decide that to mean!

 

[ban-all-sheds]

All the rest such as CUs with metal flapping lids which stay closed, special glands to seal around cables, intumescent seals inside, metal blanks for unused ways and the rest are things which certain manufacturers have invented so they can claim that their products are somehow superior to others and therefore sell more of it.

Would that be in the same sort of way that certain car manufacturers have invented things like extra soundproofing, adjustable suspension settings, lighter and stiffer bodywork and the rest so they can claim that their cars are somehow superior to others and therefore sell more of them?

 

[ericmark]

I really do hope electrical manufacturers are better than car manufactures? The VW story is quite frighting, to think they would go to such lengths to hide the facts about their cars. However I have also read the literature where manufacturers claim their RCD's are designed to trip at 80~100% of leakage settings not the standard 50~100% and give a warning before tripping. The X-Pole claims do seem impressive.

However use of RCBO's do seem to do the same thing in that they don't trip as often although without warning lamps.

I would be more impressed with a MCB or RCBO which when you open the apertures for buzz bars or cables actually force open the aperture so that errors with buzz bars ending up the wrong side of the clamp are very unlikely. This to my mind was the cause of many fires, and rather than contain the fire I would like to see the fire never starts.

As with VW it seems some manufacturers have be negligent and produced CU's or MCB's which left a possible fault just waiting for a fire. The metal CU is the result of their malpractice. OK I will admit some one building up a consumer unit one the bench before fitting had not problem. But renewing a MCB in the restricted space under the stairs it was an accident waiting to happen.

As to products the protection against spikes tripping a RCD seems to lack any data so one simply can't read data sheets it's all down to personal experience. We all know they vary and some will trip at first flash of lighting, others seem to only trip when the tester is used. Maybe they have software to detect when a tester is being used and at other time under normal use need a higher tripping current. No one would have expected VW to cheat that way so have RCD manufacturers done the same?

 

[ban-all-sheds]

The VW story is quite frighting, to think they would go to such lengths to hide the facts about their cars.

They were just the first ones to get caught.

If you have ever looked at a car advert, or specs, from any maker, seen the fuel consumption figures and thought "yeah, right", what you were looking at was a manufacturer lying about emissions too.

Maybe they have software to detect when a tester is being used and at other time under normal use need a higher tripping current. No one would have expected VW to cheat that way so have RCD manufacturers done the same?

No, for two reasons:

1. 
   There is no competition between RCD manufacturers to have shorter and shorter tripping times, so no need for pretence.
2. 
   What you propose would cost a great deal more than just making RCDs which do what they are supposed to.

 

[ericmark]

We see car manufacturers which clearly are giving out false information, Vauxhall Ampera does it do 235.4 mpg or 51.4 mpg? those are rather different figures.

OK in the electrical trade may be not as wild in their claims compared with the facts, but to expect they will be more honest with the public is being a little silly. We look at LED bulbs which we know can easy give us 100 lumen per watt, but actually give 60 lumen per watt, but both the 100 lumen per watt and 60 lumen per watt have the same energy ratting.

With mpg or lumen per watt we can if we hunt find the real data. Vauxhall do publish the fuel tank size, and the miles it will do on a charge, and it's range, so if you want you can find out real miles per gallon.

But be it CO2 emissions or resistance to erroneous tripping of an RCD if the manufacturer lies we as the consumer have no way of knowing that they lied. Each manufacturer tries to gain the trust of the consumer and once lies are exposed that trust is lost.

Had the London fire brigade published figures as to how many CU units of each make went on fire maybe we would get a completely different story? I am sure there are rouge manufacturers who just aim for profit like VW and could not care less about quality. Of course to sell the products they must look reasonable, but the harder things to qualify are not as good.

 

[deadshort]

That's a very interesting point you make eric re the number of units from each manufacturer. You would have assumed each manufacturer would be interested in obtaining that information.

However, we must accept that if the consumer unit was wired and terminated correctly, it would not go on fire, no matter what the casing is made of.

DS

 

[securespark]

Indeed. How many old wooden Wylex boards did I see that were heat-damaged, compared to the modern stuff?