Adding a second consumer unit in a extension

[cookie999999]

Hi only recently qualified and gone out on my own just landed my first big job wiring a new extension. I recomended to the client that a second cu for the extension might be a good idea as the existing house wiring is all in need of up dating and did not want to get involved with the old cu unit. The problem I have is that he wants the new cu in the new part and it is 15 meters away from the supply and meter. He has gone out without my advice and bought 20 meters of 25mm tails and earth. Which is not cheap. And I have told him that the tails should not be over 3 meters long. Could I get round this by putting a 100amp isolator after the meter then in to Henley blocks and the reconnect the old cu and then run the tails to the new cu ? Any help would be appreciated

 

[trev]

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[Tony Barnes]

Hi cookie

My view is definitely don't use metre tales I would use a 16mm twin & earth with a separate 16mm earth along side it providing this can take the load of the extention. Split the existing tales with a Henley block (ensure that you get a DPI fitted by electric board first) then supply the existing consumer unit and also a 60A fused isolator to supply extention sub main. Upgrade the bonding conductors to gas & water services if required.

Hope it helps

 

[Octopus]

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5 if you don't have your tester with you!

 

[GMES]

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I was only joking Trev but it may just be the future!!

 

[Guest77]

This is Electrical Forums.

Press 1 for new shed supplies
press 2 for exporting PME
Press 3 for distribution board changes
Press 4 for shared neutrals
Press 5 for changing lights with no earth wires
Press 6 for faulty RCDs

pmsl haha

 

[HandySparks]

What existing earthing arrangement is in the house?
is there any bonding main or supplementry anywhere?
how are you planning to run the cables?
have you told the house owner to take the tails back yet and get some proper cabling for the job?
are you registered with a scheme to sign off the work?
have you got a MFT?
What insurance have you got?
what load is going into the new extension?

Good point. I may not have asked ALL those questions, but there's a fair amount of info missing.

 

[davesparks]

Nooooooooooooo!!! Please not this one again.

Not what one? Asking what is wrong with the existing installation? Or stating that the bonding will need upgrading as a matter of course? Or asking what he has recently qualified as?

They all seem to be perfectly relevant questions, and the OP even gave me a thanks for that post!

 

[davesparks]

how big is the extension/whats going in there to require 25mm? IMO running a swa over to new consumer unit is a lot of effort and cost when you could just run the new circuits from the extension (same route you would of prob used for swa/tails)and put them on its own consumer next to existing consumer unit. plus you will have to install bonding to gas and water if not already in place.

Or else it is entirely possible that extending the existing circuits may be all that is needed.

But we'll probably never get to find out unless the OP reappears.

 

[Guest77]

Not what one? Asking what is wrong with the existing installation? Or stating that the bonding will need upgrading as a matter of course? Or asking what he has recently qualified as?

They all seem to be perfectly relevant questions, and the OP even gave me a thanks for that post!

They were, nothing wrong with them at all.

 

[Engineer54]

Why a separate CU for an extension?? If the existing installation needs cleaning up at the existing CU's location then so be it, clear it up and install a suitable sized CU in the process....

As has already been pointed out, some existing circuits could well be extended into the extension saving both money and time... Never understood this mentality that house extensions and the like need a remote separate CU!! It's far more like, it just makes things easier for the installer, and nothing much else matters. It would have to be a bloody big place before i'd contemplate installing remotely located CU's in a domestic house!!!

 

[Guest125]

Why a separate CU for an extension?? If the existing installation needs cleaning up at the existing CU's location then so be it, clear it up and install a suitable sized CU in the process....

As has already been pointed out, some existing circuits could well be extended into the extension saving both money and time... Never understood this mentality that house extensions and the like need a remote separate CU!! It's far more like, it just makes things easier for the installer, and nothing much else matters. It would have to be a bloody big place before i'd contemplate installing remotely located CU's in a domestic house!!!

I think it is a get around for requiring to bring the the existing installation upto current standards with a DB change. Don't touch any of the existing circuits no need to test and give the owner a load of bad news. (Potentially)

 

[Leesparkykent]

most of the time it comes down to cost and some customers are not willing to spend money on the existing installation, even tho they should! seen it plenty of times, they just see it as its worked fine for x amount of years.

 

[andyelectric]

My suspicion is that the original cu is a wylex rewireable, and makes the inexperienced op (possibly) wrongly think some rewiring is required to the original circuits. I am with E54 in that the new seperate CU is probably the wrong way to go. But as often happens the op has disappeared so it is crystal ball time.

 

[jase]

As has already been mentioned, no need to touch the existing installation, just split the tails at the meter, put a new 2w cu in for the extension and run in power and lighting circuits. Job done. Check the bonding and install if missing as this is a requirement of any job regardless of wether you're running in a new lighting circuit or a new sub-main!

 

[davesparks]

As has already been mentioned, no need to touch the existing installation, just split the tails at the meter, put a new 2w cu in for the extension and run in power and lighting circuits. Job done.

No need for bonding or a single point of isolation in your regs book then?

 

[Simlec]

I want to know why Tony would install a 16mm Earth alongside the 16mm T+E ?

 

[TJ Anderson]

I want to know why Tony would install a 16mm Earth alongside the 16mm T+E ?

I thought the same. Maybe he gets Nectar points when he spends on materials?

 

[davesparks]

I want to know why Tony would install a 16mm Earth alongside the 16mm T+E ?

You've had me reading through the whole thread looking for a post by Tony, thinking that doesn't sound like him at all, only to realise that there is someone else of the same name on here.

It does seem like a daft idea doesn't it, and if you did need a 16mm earth it would surely be cheaper to get a cable with a full size earth like NYYJ or similar

 

[ayjay]

I want to know why Tony would install a 16mm Earth alongside the 16mm T+E ?

me too-- overkill i suspect

 

[Simlec]

You've had me reading through the whole thread looking for a post by Tony, thinking that doesn't sound like him at all, only to realise that there is someone else of the same name on here.

Lol yes not that Tony

TJ, I bet the staff at his wholesale always greet him with a bit smile.