ground floor power sockets routed off Upstairs ring...

[mbga9pgf]

Quick one,

can anyone tell me whether the current wiring configuration in my house meets regs?

Effectively, we have extensive solid oak flooring which has been professionally laid. Post flooring installation, it appears as if the leccy has installed some power sockets using the 1st floor socket supply.

Now, I cant see too many problems with this, other than it means the labelling on the CU mcbs is completely wrong. Which, if someone was having a slow day, could mean they think they have isolated the downstairs power when in fact the sockets are live.

I am intending to sort this out in the near future but for now can anyone simply say whether this is clearly against regs?

Other minor issue we have, the annexe attached to the house has a power supply connected to the Main fuse box. The cable has its own MCB protection, rated at 100A, fair one. HOWEVER, rather than istall a seperate RCD on the annexe CU, the leccy has installed the 100A MCB on the 20ma RCD side of the Main CU box.

Again, I will be sorting this, it works, but does it meet current regs? Only downside I can see is that the cooker/light/eleccy gates/garage mcbs are connected to the 20ma RCD protecting the house.

One thing I dont understand, we have some bare wiring in the garden (garden lights, disconnected using bolt croppers and having own supply at the annexe CU). When switched on at the annexe CU, this is tripping the "Garden Light" MCB and not the 20ma RCD. Why is the 20 ma RCD not tripping instead?

Diagram below:

Main supply ---- Main CU ---- 20ma RCD --------- Annexe CU (No 20ma protection)---Garden light MCB -------- garden cable

Thanks all in advance.

 

[ericmark]

Due to limitations on ring main length some houses are wired side to side rather than up and down and as long as area permitted is not exceeded and the CU is correctly marked it is really no problem.

As to supply from RCD side of consumer unit really no longer any option as cables buried less than 50mm deep need to be special cables or RCD protected.

As to short circuit this will not trip a RCD unless to earth. The RCD measures power out and power in and if within 15ma of each other it will not operate. Somewhere between 15ma and 30ma it should trip and at 150ma it must trip within 40ms. Both on pos and neg half of cycle. When you read the 63A on a RCD it refers to max amps under normal operation not tripping amps. and the 4.7k refers to max let through amps. Trips that measure current usage and will trip with overload normally have the letters B, C, or D in front of the amps so a B16 will eventually trip with 16A and will trip very quickly with 80A (5 x 16).

 

[mbga9pgf]

I am planning to re-route the supply from the main CU to the annexe CU via electrical conduit along the external wall.

Will it still require RCD protection? It seems pointless to lose the main house RCD circuits because of a snag on the annexe circuit. annexe currently connected using 3/4 inch steel armoured cabling but looks butt ugly, hence the move towards electrical conduit. If we are adjusting the connections into the CU, would there be any issue with connecting the annexe supply to the 100ma RCD instead then installing a 20ma RCD in the annexe? Seems to make more sense this way to me?

As for the labelling on the CU regards upstairs/downstairs its definitely incorrect, plus we definately have upstairs/downstairs MCB protected loops; I spent the weekend constructing a wiring diagram of the house and managed to notice these issues.

 

[ban-all-sheds]

Effectively, we have extensive solid oak flooring which has been professionally laid. Post flooring installation, it appears as if the leccy has installed some power sockets using the 1st floor socket supply.

Would you rather he had pulled up parts of your solid oak flooring?

Now, I cant see too many problems with this, other than it means the labelling on the CU mcbs is completely wrong. Which, if someone was having a slow day, could mean they think they have isolated the downstairs power when in fact the sockets are live.

They could, but you could easily fix the labelling on the CU. And slow day or not, anybody working on electrical circuits should learn, and carry out, safe isolation procedures.

I am intending to sort this out in the near future but for now can anyone simply say whether this is clearly against regs?

Apart from the CU labelling it's absolutely fine. And if you want to rewire it there's no reason (except, possibly, circuit length) why you can't have those sockets on the same downstairs circuit as the others but keep the cable routing.

Other minor issue we have, the annexe attached to the house has a power supply connected to the Main fuse box. The cable has its own MCB protection, rated at 100A, fair one.

A 100A MCB? Really? What size is the cable?

HOWEVER, rather than istall a seperate RCD on the annexe CU, the leccy has installed the 100A MCB on the 20ma RCD side of the Main CU box.

20mA? Really?

Again, I will be sorting this, it works, but does it meet current regs?

Is the main CU is designed to take a 100A MCB?

Is the cable rated at 100A?

Only downside I can see is that the cooker/light/eleccy gates/garage mcbs are connected to the 20ma RCD protecting the house.

Have your electrician change it: split the tails, switchfuse for the annexe CU supply, RCDs/RCBOs in the annexe CU.

One thing I dont understand, we have some bare wiring in the garden (garden lights, disconnected using bolt croppers and having own supply at the annexe CU). When switched on at the annexe CU, this is tripping the "Garden Light" MCB and not the 20ma RCD. Why is the 20 ma RCD not tripping instead?

You've got a L-N fault not a L-E or N-E one, so there'll be no imbalance for the RCD to detect.

http://en.wikipedia.org/wiki/Residual-current_device


Please turn off the supply to the annexe CU, disconnect the garden light cable from its MCB and remove it from the CU. ASAP!

 

[mbga9pgf]

They have used 1000V rated armoured cabling, not sure of the max current rating. Its between 1/2 to 3/4" thick though and wouldnt go amiss as an umbilical for the apollo rockets...

Here is a pic:
http://s979.photobucket.com/albums/ae271/mbga9pgf/?action=view&current=IMG_2553.jpg

Oh, its routed over the top of the soil, through the borders and up the wall into the annexe.

The annexe has a 10Kw power shower, lots of hideous halogen downlights, an electric cooker.... then the annexe links in series to the Garage and timber workshop, which then links in series to the eleccy gates. I think 100A is not a bad guess.

THe lights still dim somewhat though when the shower is on, we live in the sticks so it is to be expected with oh power cable supply I suppose.

I am digging up the garden armoured cabling in sections, although the idea of having these

http://www.screwfix.com/cats/A331915/Electrical-Supplies/Switches-Sockets/Weatherproof

means I may flag, strap and wirelock the MCB supplying the cable instead.

 

[ban-all-sheds]

I am planning to re-route the supply from the main CU to the annexe CU via electrical conduit along the external wall.

Oh yuck.

Why not bury it?

Will it still require RCD protection?

The cable itself? No.

It seems pointless to lose the main house RCD circuits because of a snag on the annexe circuit.

Absolutely.

And arguably not compliant with the regulations.

Who did the installation? When? Is the annexe a new addition? What electrical certificates were issued? Is there a Building Regulations completion certificate for it?

annexe currently connected using 3/4 inch steel armoured cabling

Unlikely to be large enough to be on a 100A breaker - another ASAP job to be done.

but looks butt ugly, hence the move towards electrical conduit.

SWA is round and black. How is that any uglier than conduit?

If we are adjusting the connections into the CU, would there be any issue with connecting the annexe supply to the 100ma RCD instead then installing a 20ma RCD in the annexe? Seems to make more sense this way to me?

It would be better for it to be taken off the main CU altogether.

Why have you got a 100mA RCD? Do you have a TT supply? Is the annexe a separate building? How far away is it?

 

[mbga9pgf]

Oh yuck.

Why not bury it?

Its partially buried at the mo. not very well though. At least solid conduit looks relatively orderly and can be painted to match the house render. That was the plan anyways. Burying may be an option.

Who did the installation? When? Is the annexe a new addition? What electrical certificates were issued? Is there a Building Regulations completion certificate for it?

The annexe was completed in 2003, was never signed off officially and I am picking up the issues now to get sorted prior to our move in date. The construction is all fine, although we didnt get a single leccy certificate when we moved. We are not planning to move from here for a very long time. The electrics and CU wiring are all fine, no major snags there, I havent seen anything that really worries me at the moment. But I want it RIGHT before we move in next July.

Unlikely to be large enough to be on a 100A breaker - another ASAP job to be done.

NB'd thanks. Where can I purchase 100A cabling though? with the shower running at 45A, the cooker probably at around 30-35A (no lpg piping to annexe kitchen) and the billions of 50w halogens they have in the place, we arent going to be far off tripping the 100A MCB, when you factor the eleccy gates and garage also are routed off the annexe supply. We have no heavy duty equipment in the garage or timber workshop though, just fluorescent strip lights and a bench grinder. Gotta factor in what OTHERS might put in though too.

It would be better for it to be taken off the main CU altogether.

Why have you got a 100mA RCD? Do you have a TT supply? Is the annexe a separate building? How far away is it?

you mean route it off the cable from the 200A protected supply instead of taking it from the main CU? Not a bad idea.

Yes, we have TT. Country area so no TN

 

[ban-all-sheds]

They have used 1000V rated armoured cabling, not sure of the max current rating. Its between 1/2 to 3/4" thick though and wouldnt go amiss as an umbilical for the apollo rockets...

Could be 1,000,000V cable - that's irrelevant. What matters is the current rating, and 1/2 to 3/4" thick means that it is not large enough to be on a 100A breaker.

• //www.diynot.com/wiki/electrics:mcbtocable
  
  
• http://www.tlc-direct.co.uk/Book/4.3.1.htm
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/cableselection_web.pdf[/list]
  

  Oh, its routed over the top of the soil, through the borders and up the wall into the annexe.

  Unsatisfactory.
  
  
  

  The annexe has a 10Kw power shower, lots of hideous halogen downlights, an electric cooker.... then the annexe links in series to the Garage and timber workshop, which then links in series to the eleccy gates. I think 100A is not a bad guess.

  Your electrician will advise.
  
  
  

  THe lights still dim somewhat though when the shower is on, we live in the sticks so it is to be expected with oh power cable supply I suppose.

  No it's not. Far more likely is that the cable running to the annexe is undersized for the load, so as well as not complying with In ≤ Iz it's also failing on Ib ≤ In.
  
  • http://www.tlc-direct.co.uk/Book/4.3.11.htm
    
    
  • http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html[/list]
    

    I am digging up the garden armoured cabling in sections,

    It needs wholesale re-design and replacement, not tweaks to bits of it.
    
    
    

    although the idea of having these
    
    http://www.screwfix.com/cats/A331915/Electrical-Supplies/Switches-Sockets/Weatherproof[/QUOTE]
    MK, not Clipsal.
    
    
    

    means I may flag, strap and wirelock the MCB supplying the cable instead.

    ¿Que?
    
    
    Overall, given the changes needed, you should be getting an electrician in.

 

[ban-all-sheds]

The annexe was completed in 2003, was never signed off officially and I am picking up the issues now to get sorted prior to our move in date.

Get a comprehensive PIR done.

The electrics and CU wiring are all fine,

You might turn out to be right, but given what you've found so far your confidence is misplaced.

Where can I purchase 100A cabling though?

Your electrician will be able to get it at the wholesaler(s) he normally uses, and at a better price than you can get.

But you should look to reducing the demand of the annexe - you could start by doing something about all that lighting.

How is the annexe heated?

you mean route it off the cable from the 200A protected supply instead of taking it from the main CU?

You've got a 200A single-phase supply?

Yes, we have TT. Country area so no TN

Ask your electrician to check if TN-C-S is available - quite a few TT supplies have been converted. If you are sticking with TT then possibly the outbuilding should have its own earth, not one exported from the house.

Again, your electrician will be able to advise.

And you're going to need a "real" electrician. As ever, personal recommendations are always the best way to find a reputable tradesman, but if you're having to go ahead without much in the way of those, or references, don't put any store by registration itself - sadly it is possible to become registered with woefully inadequate qualifications and zero practical experience. You don't have to spend long here to see people cropping up who are registered and "qualified", but who are clearly seriously incompetent in reality and who should not be charging for their services.

It's your money, possibly quite a lot of it, and you have every right to ask prospective tradesmen what their qualifications are. Just being listed here is not a good enough guide. No genuinely experienced electrician, with the "full set" of C&G qualifications will mind you asking - in fact he will wish that everyone was like you.

I feel sorry for people who have been misled by training organisations and (shamefully) the Competent Person scheme organisers into thinking that a 5-day training course, a couple of trivial examples of their work and some basic understanding of how to use test equipment will make them an electrician, but not sorry enough to agree with them trying to sell their services to Joe Public.

 

[mbga9pgf]

Unsatisfactory.

YEs, aware of this, yet I couldnt seem to get an answer on which reg it didnt comply with on a separate thread, as some individals on here tow the "knowledge is power" line whilst giving out zero useful information

Your electrician will advise.

I am sure he will.But in order to estimate materials costs, I need to be able to work out adequate cable diameters, which I am sure my leccy will do, but as I dont want to get ripped off for overinflated materials charges, I am trying to cost this now. Choice being 80A MCB and 16mm cable or 100A and uber expensive 25mm cable.

It needs wholesale re-design and replacement, not tweaks to bits of it.

No, it needs ripping out and disconnecting from the CU to be honest. I dont intend to use it if it creates too much hassle and I aint paying leccy hourly rates for him to dig up a cable that is isolated and I can do myself. If the cable is dug up, then all he has to do is isolate from the CU, which I am sure he would prefer.

MK, not Clipsal.

Cheers, useful advice.

You've got a 200A single-phase supply?

yep, off overhead cables. Supplier main fuse is protected at 200A.


The annexe is heated using gas CH, but as you would expect having just bought, are skint, so major expensive improvements and certs will have to wait. So unfortunately, annexe is remaining on elec cooker until we can afford for the gas supply to be extended to the kitchen.

CERTIFIED family worker used to working on 3 phase HV and electrical installations but who is competent to do house work is doing the work fortunately (paid).

what bonus would TN-C-S give over TT other than not having to have an earthing spike (thats been successfully tested for impedance)?

 

[ericmark]

Something does not seem right!
1) The biggest MCB I have used is around the 63A after that moulded circuit breakers seem to be only option. Most makes 50A seems limit.
2) Most consumer units are rated at 100A and to have a bigger unit one has to leave the type tested consumer unit and use a distribution unit.
3) To use two 100A consumer units on a 200A supply one would need to have some fusing before the consumer unit in the past I have used a 200A switched fused isolator to feed three consumer units each through it's own 100A fuse.
4) RCD's tend to go up in size by a factor of three so 10ma, 30ma, 100ma, and 300ma are common but a 20ma RCD would be a rare beast.

Now although I could in theory use a 100A mounded breaker the problem is many models have setting which the electrician can alter to suit. As a result the access can only be given to a qualified person and to have a lock on the moulded breaker would not really be the answer. Hence why I used a fuse.

In general something seems wrong. There are of course farm houses where there are many out buildings all supplied from the general farm supply and there will be a selection of consumer units/distribution boards controlling the whole system and these are in turn often feed from a step down transformer dedicated to the farm. Two systems are common, three phase and split phase and by using this method 200A or 300A can be supplied through two or three fuses and no single supply is over the 100A that a consumer unit can handle.

Odd systems are often a result of some historic supply. Where some building has had change of use or even new building on site of old. And where this has happened one can get some strange set-ups. In which case it does really need some one on site giving you help not on a forum like this.

As to the three supply systems personally I don't like TN-C-S as I have seem the result of a broken neutral and feel all too often the supplier does not follow the rules however often we have no option.
The TN-S is the preferred method giving a very good ELI but without the dangers of the TN-C-S system. However looking at your pictures I see no surrounding housing and with both systems the boards earth and true earth could vary enough for a TT supply to be considered. Again the size of the supply may mean different considerations to normal and although if on site I would select the best option I don't feel this is something that should be done remote and you should be asking some one who is on site not a forum.

 

[Jacobssi]

I agree with BAS about the qualified electricians. I'm one of them, I've done my qualifications privately but still wouldn't trust myself to do a job on my own!! I feel I have enough knowledge without experience to assist but nothing more. People jump to far ahead, personally I'm going to get many years experience before I go solo, it's a scary world. Sorry to deviate

 

[mbga9pgf]

I agree with BAS about the qualified electricians. I'm one of them, I've done my qualifications privately but still wouldn't trust myself to do a job on my own!! I feel I have enough knowledge without experience to assist but nothing more. People jump to far ahead, personally I'm going to get many years experience before I go solo, it's a scary world. Sorry to deviate

Its only a scary world because you dont hold one vital ingredient; experience. That comes with practice. Whilst I agree I am not qualled to carry out all the work, there are minor issues I can sort out, leaving the big bad stuff like taking the CU apart for the pros. For example, I can look through the regs, attach the conduit to the wall then route the wiring to both CUs without connecting, then get my qualled family member to connect up all the bits and bobs without compromising safety. Same vis a vis digging up half a mile of armoured cable in the garden and leaving the pro to disconnect.

Behemoth regulation doesnt help; you do wonder whether the IEE are re-writing regs these days to justify their own existence, the ultimate self licking lolipop. I come from the aviation industry, one of the most heavily regged industries in the world, and whilst common standards and work practices are to be commended and help each other out, some of the regulatory and sign off nonsense they have generated seems to have done little more than as I say, get in membership fees and justify their existence.

As for the current rating on the CU, I will take some pics when I am at the pad this weekend. Hopefully will clear up a few posters I have confused, having thought what you have said above, the fact that all the CUs have 2 main 100A MCBs suggests I may be on 2 phase.

 

[ban-all-sheds]

the fact that all the CUs have 2 main 100A MCBs.

I predict that they don't.

I predict that they have 100A rated main switches.

I sincerely hope that the person who did the annexe installation has not taken the supply directly from one of the incomers.....

 

[mbga9pgf]

the fact that all the CUs have 2 main 100A MCBs.

I predict that they don't.

I predict that they have 100A rated main switches.

I sincerely hope that the person who did the annexe installation has not taken the supply directly from one of the incomers.....

No they didnt. Why wouldnt you do this though if it was RCD protected at the annexe CU?

Its currently routed via a 100A MCB on the 30ma RCD side.