TT Installation - Moving CU

[quick]

Hi all,

I am in the process of re-wiring a small domestic unit in the middle of nowhere which has a overhead TT supply. The meter is outside and backs onto the bathroom, the previous installation had 16mm meter tails through the cavity upstairs to a 30ma RCD and small re-wirable fuse board, which had several sub-mains wired in t+e to cu downstairs.

My intention was to move the CU downstairs for convenience about 4m away or 7m from meter, but this would mean a sub main as the meter tails would be over 3m long. I know you can use a switch fuse and SWA to new cu (30ma split load) and protect the SWA using 100ma s type RCD, but this is very expensive.

Question

Could I do as it was originally and put a 30ma RCD and switch fuse (60a) at meter tails (upstairs), use 16mm t+e for sub main and then have non RCD cu downstairs for all circuits. As the 30ma RCD would protect the entire installation.

Or would you advise putting the cu upstairs where the meter tails come in and using a 30ma split load board there (low level).

Either way if the RCD trips you have to go upstairs maybe in the dark! to reset which is not ideal.
(Maybe Emergency light at top of stairs )

Any advise would be appreciated.

Many thanks.

 

[jimjimjim]

Could I do as it was originally and put a 30ma RCD and switch fuse (60a) at meter tails (upstairs), use 16mm t+e for sub main and then have non RCD cu downstairs for all circuits. As the 30ma RCD would protect the entire installation.

.

You've answered your own question (which the answer is no btw) Reg 314.

Put the CU upstairs and segregate the lighting. An e-light is a good idea


Jim

 

[Engineer54]

First thing i'd do, is walk along the overhead poles and see if the overhead supply had been PME'd. Don't think i'd like the meter located upstairs myself, that means meter readers will have to trample through the house to read the damned thing.

Why can't you run a SWA/NYY cable from the overhead position on the house, down the wall to an outside meter cabinet and then come indoors to a suitable CU position.... Can't see that costing too much on the DNO side of things!!

 

[quick]

First thing i'd do, is walk along the overhead poles and see if the overhead supply had been PME'd. Don't think i'd like the meter located upstairs myself, that means meter readers will have to trample through the house to read the damned thing.

Why can't you run a SWA/NYY cable from the overhead position on the house, down the wall to an outside meter cabinet and then come indoors to a suitable CU position.... Can't see that costing too much on the DNO side of things!!

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Sorry if miss under stood, meter cabinet is outside ground floor on wall that backs onto bathroom that is why they have run the meter tails up the cavity wall to a position upstairs using about 2-3 meters of tails. There is nowhere else within 3m of meter that is suitable.

Either way the tails would still have to follow the same route and kit for potential sub main put upstairs the possible downstairs cu would only be about 4 meters from the upstairs position. But my problem is the expense ect involved with sub mains on tt systems.


Thanks for your reply Jim, upstairs consumer unit on split load board does sound better than rcd upstairs and non rcd board downstairs at least you could divide the circuits. Just seems overkill to go down the route of time delayed rcd,swa etc its basically a 1 bed detached house like an old telephone exchange i think.

Anyone had this before?

Thanks for the replys

 

[Engineer54]

If the DNO head and meter is downstairs, why the hell are you thinking of leaving a CU upstairs??
If this is such a small house, provide an all RCBO CU for the whole installation, all this crap about a CU upstairs and another downstairs beggers belief for a one bedroom house!! A time delayed (S type)100mA RCD is a very sensible addition to any TT system, it provides back-up for U/S RCD's....

 

[quick]

If the DNO head and meter is downstairs, why the hell are you thinking of leaving a CU upstairs??
If this is such a small house, provide an all RCBO CU for the whole installation, all this crap about a CU upstairs and another downstairs beggers belief for a one bedroom house!! A time delayed (S type)100mA RCD is a very sensible addition to any TT system, it provides back-up for U/S RCD's....

Reason i keep saying upstairs is thats where 3meters of tails would take you to a suitable position above the bathroom to keep it downstairs it would have to come through the ceiling joists of the bathroom and the tails would be about 5 meters long minimum.

I agree the multi board setup is stupid i only want one board and spilt load boards are quite cheap now rcbo only board for even 4 or 5 circuits would cost more?

so you think s type RCD upstairs where 3 meters of tails reach and sub main to small cu?
or s type RCD in meter cupboard?

 

[Guest55]

i have to ask but........

what are the customers reasons for moving the CU in the first place ?
what will it achieve ?
whether the cu is upstairs or downstairs is neither here nor there really as how many times does a homeowner need to access the cu on average ?
2-3 times a year at most i reckon so hardly worth the expensive of re-routing lots of cabling.

am i the only one on here who considers the bleedin obvious ? lol

 

[MDJ]

Captin Part P strikes again Biff, they need to feel the need to alter things lol

 

[Engineer54]

i have to ask but........

what are the customers reasons for moving the CU in the first place ?
what will it achieve ?
whether the cu is upstairs or downstairs is neither here nor there really as how many times does a homeowner need to access the cu on average ?
2-3 times a year at most i reckon so hardly worth the expensive of re-routing lots of cabling.

am i the only one on here who considers the bleedin obvious ? lol

As this is a full rewire, ''Do it Once and do it Right springs to mind!! lol!!


To the OP, .....Up Front, normally means before any final circuits!!

http://www.shop-we.co.uk/

If were talking about a smallish CU, check this site out, (CU/Isolator + 5 RCBO's) and tell me it's an expensive exercise, especially when considering it's for a TT installation....

 

[quick]

i have to ask but........

what are the customers reasons for moving the CU in the first place ?
what will it achieve ?
whether the cu is upstairs or downstairs is neither here nor there really as how many times does a homeowner need to access the cu on average ?
2-3 times a year at most i reckon so hardly worth the expensive of re-routing lots of cabling.

am i the only one on here who considers the bleedin obvious ? lol

Agree was only going to move it as it was a strange position to have it and not the norm, split load to divide the lighting or rcbo board upstairs thinking about it prob not all that bad