Consumer Unit Positioning

R

ryanj

During my rewire, I plan to move my consumer unit to a new position. Currently, it is in a room with a concrete floor, I propose to move it to allow me to get cables into the crawlspace easier.

My supply is an overhead TT supply. Would it be acceptable to simply run 25mm sqr metre tails from the metre in the old position to the new consumer unit, or would I have to contact the power company to move the metre beside the consumer unit?

Also, is it fine to have earth rods driven from the crawlspace, rather than have them taken outside? And must I use a "whole-house" RCD, if I can get the earth fault loop impedance low enough?

And, is it acceptable to use a flush consumer unit in domestic situations, as it'd help keep everything neat?

And, is it acceptable to run cables in the crawl space without clipping them to the joists, or running them through the joists?

Finally, where the cables leave the consumer unit, do the cable grouping de-rating factors take effect for 1-2metres down the wall?
 
Sponsored Links
Joined
28 Mar 2004
Messages
9,883
Reaction score
445
Country
United Kingdom
you aren't meant to run tails more than 3m without having your own isolation and protection

the main rcd for a TT must be in a plastic enclosure

you could use a plastic 4 module enclosure with the 100ma type S rcd and a 100A mcb (http://www.tlc-direct.co.uk/Products/CMDK401.html)

then run from that to a normal split load CU preferablly using 25mm swa
 
Sponsored Links
Joined
6 Oct 2003
Messages
701
Reaction score
1
Country
United Kingdom
Go for what plug suggested, creating a distribution circuit, have the position where you want then.....
 
R

ryanj

Thanks! Got that problem sorted out.

Any advice on the others?
 
Joined
6 Oct 2003
Messages
701
Reaction score
1
Country
United Kingdom
You can have the rod in the crawl space as long as its <100Ohms. (Make a label stating the location)

Not to sure what you mean about the RCD, but a TT system requires that the installation is protected by an RCD usually 100mA although a 30mA is required for supplementary protection.

Cant see a problem with using a flush mount DB

Clip the cables in the crawl space

Grouping factors for that amount of lenght shouldn't be a problem.
 
R

ryanj

TT system requires that the installation is protected by an RCD

Are you sure the whole installation must be protected?

The only thing I can find in the regulations states that all socket outlets on a TT system must be RCD protected. Nothing else.

471-08-06 - Where the measure is used in an installation forming part of a TT system, every socket-outlet circuit shall be protected by a residual current device and shall comply with Regulation 413-02-16
 
Joined
28 Mar 2004
Messages
9,883
Reaction score
445
Country
United Kingdom
yes but you will never meet disconnect times otherwise

the impedcence of the earth limits the current flow down it to a value insufficint to trip a fuse or mcb

that is why you need the main rcd
 
R

ryanj

But, if i could reach required disconnection times, would I need to use a main RCD?

Also, could I run meter tails instead of using SWA?
 
Joined
28 Mar 2004
Messages
9,883
Reaction score
445
Country
United Kingdom
tails would probablly be ok but they should be protected from damage

a worst case allowed TT is 200 ohms this will allow just over an amp to flow in the case of a short to earth (obviosuly until this fault is disconncted your entire earth system will be live so it should happen asap)

so either a rcd is essential OR it would have to be a bloody good TT (like big mats burried below the water table)

with a ROD you will not manage it
 
R

ryanj

Crawlspace - Small area under the floorboards of the ground floor.
 
Joined
28 Mar 2004
Messages
9,883
Reaction score
445
Country
United Kingdom
it would be an insanely stupid place to put a rod

to get a usable earth the rod needs to be at least partially in wet soil
 
R

ryanj

Fine, I'll use multiple earth rods in the back garden to try and keep the resistance low.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Top