Supplying distribution board regs

[green-sparky]

Hi, recently done quite a big house rewire, which required 2 distribution boards. The house has a 3 phase supply with the distribution boards located in cupboards directly above each other. I supplied the boards with 2 separate pairs of 25mm double insulated tails and used trunking to house them in while going from the ground floor to upstairs.

The problem being now is that another company has went in and said to the client that this is wrong and the upstairs board should be supplied by a SWA, is this correct? Or is there away to get round this by adding in a RCD straight after the supply isolator as the only place the tails aren't protected are when they pass through the floor space?

Thanks.

 

[londonlec]

Two pairs of tails, so what does the third phase do?

I don't think its non compliant, but not the way I would have done it either TBH.
SWA probably would have been cheaper/quicker for you.

 

[Amp David]

If your tails are run all the way in trunking and are sized correctly and fused correctly, then can't see an issue. Are the DB 3 phase?

 

[green-sparky]

There is a 3 phase isolator with the neutral going to a neutral block, with the phases supplying separate single phase boards. The only points where the tails are not protected are for roughly a metre in the cupboard and as the trunking stops at the ceiling, the tails go unprotected through the floor before going back into trunking upstairs. Is there anywhere I can find something to back up this is ok as I have to give them an answer by tomorrow?

 

[needasparks]

Don't think i would have done it either, if the cupboards were that close why a board in another location.
I can understand local supply board if this was com/ind or a long distance run making shorter run sub-circuits.
I'm sure you have your reasons for this but would be good for us to know them as we don't know the job but it would help to give you a better answer. From your post these tails are protected via the cut-out fuse, Yes ?

 

[robsparky1975]

Dont have my regs to hand but is it not the case that if the meter tails are over 3mtrs then they require some form of protection ie not relying on the cut out fuse,unless i misread your post,how long are they to the consumer units?

 

[green-sparky]

They wanted separate boards for upstairs and downstairs, don't know why. The supply goes through the pull out fuses to a 3 phase plastic isolator, I have then took the tails from this isolator to each board, is there a regulation that you can't run double insulated supplies through floorboards as that is the only thing I can work out that they may have a problem with?

 

[green-sparky]

The tails going upstairs from downstairs are roughly 10 metres by the time they go through the trunking.

 

[i=p/u]

as you have in trunking, id say your fine, but some will say switched fuse should of been used as is over 3m..... but your 100A fuse is protecting 25mm tails...

whats the 3rd phase powering???????

 

[green-sparky]

as you have in trunking, id say your fine, but some will say switched fuse should of been used as is over 3m..... but your 100A fuse is protecting 25mm tails...

whats the 3rd phase powering???????

The 3rd phase isn't powering anything.

 

[thekingiam]

not much worked on three phase in a domestic, would you have to balance the loads on each phase?

 

[Knobhead]

Why haven’t you used three phase boards and balanced the loads? Seems a waste to me.

 

[i=p/u]

suppose in most places you go they are never actualy balanced, just by breaker size and not actual loading...

 

[needasparks]

Why haven’t you used three phase boards and balanced the loads? Seems a waste to me.

Always good to have a spare.

 

[robsparky1975]

10 mtrs you say,but its the dno who owns the cut out fuse and they give 3 myrs as a max, so anything after the cut-out is down to you so theoretically the tails are not protected by a means of protective device provided by you,i can see why someone would see a problem there,if i inspected it to be honest i think i would want to see some form of switched fuse for each sub main to each consumer unit.

 

[green-sparky]

It was the way it was before, its not that big a house so to add a third board which would be powering practically nothing anyway seemed pointless.

 

[green-sparky]

Also on the list was the fuseboard upstairs not being allowed to be fixed to a wooden board as it is a combustable material, isn't this a it OTT?

 

[needasparks]

Sounds like for the owner to get someone else in and make a list on your work they may have their doubt's on the installation.
Has there been problems here ?

 

[thekingiam]

as stated previously i have not much experience in domestic three phase domestic so please take what i say with a pinch of salt, i would of guessed at a three phase board in cupboard where original was and took a feed from that board,which would of been protected via a rcbo to single phase board on other level. thus keeping with dno's regs on 3 metre tails to board and also protecting cable faults to other board.

 

[green-sparky]

Sounds like for the owner to get someone else in and make a list on your work they may have their doubt's on the installation.
Has there been problems here ?

Separate companies involved, I had the contract to rewire the house with another company coming in after to install fire alarms and emergency lighting as it's to be used to house homeless teenagers.

 

[thekingiam]

although it's a domestic setting it's a setting for as many teenagers they can fit in as little spaces as possible, so more of a commercial rewire should of been budgeted for.i would of guessed that the local labc would look at everything in close scruitiny as well as other bodies such as the fire department.not using swa for a start, although not always needed may have already started alarm bells ringing as they may be worried that you have cut corners in other places.i will leave the rest if any technical details to someone like telctrix if he is here or lenny or eng54 or the many others that must be drinking in the pub

 

[Des 56]

If your tails are run all the way in trunking and are sized correctly and fused correctly, then can't see an issue. Are the DB 3 phase?

Thats about all that needs to be said

There is no reason to say you have to use swa unless mechanical protection was required,then swa would satisfy that,but that protection could also be given to tails
Cables in trunking is an accepted method of installation,with the tails they should be supported,clipping them in the trunking should do

You would do well to fit switch fuses for each set of tails after the 3 phase isolator,the supplier may insist on you providing your own overcurrent for the extended tails

Rather than you trying to find a reason
Ask them to specify the reg No that stipulates that swa should be used as an exclusive method of install,put the ball on their foot rather than yours

 

[Deleted member 26818]

No real need for SWA, the trunking provides mechanical protection.
It's not normal to provide mechanical protection for cables when they're run under floors or above ceilings. Is there evidence of excessive rodent activity?
The only problem that I can forsee, is as others have indicated, the length of the tails.
The DNO might not like it, although the cable and the reference method allows up to 101A. What are the ratings of the fuses?