Tidying up our supply wiring

[jayc89]

One of the first things we did when we got the keys to the house was have it re-wired. In hindsight I wish we'd held off as there are a couple of things I'd do differently now. One being this monstrosity by the side of our front door;

 

In an ideal world, we'd;

- Bring the supply (black cable, painted white) in within the first floor void, slightly above it's current location.

- Move everything else to our under-stair cupboard. Approx. 8m from the current location

 

I understand to move anything up to, and including the meter that far, I'd need to contract Northern Powergrid, which sounds expensive. I also understand the meter tails can't be longer than 3m, so I think that means, realistically, I'll have to leave everything to the right (mounted to that piece of wood), where it is, but I can get my sparky to move everything else?

 

Are there any other solutions short of forking out, who knows how much, for Northern Powergrid to move the meter et al ?

[TonyT]

Meter tails can be longer than 3m but you need to add your own protective device. Ie a fuse.

 

probably best to make a nice looking box with door paint accordingly since you’ve already had the property rewired

 

[andyscotland]

As with @TonyT I would say personally at this stage I'd just box it in.

 

If you really wanted to move it then getting the DNO to move the intake/meter to your understair cupboard could well be prohibitively expensive (especially as I assume that is further from an external wall so they will have to get the cable neatly through the house / under the floor).

 

A better option might be to get them to relocate the supply to an external box/kiosk (so they are shortening rather than extending the cable). Your electrician would fit a fused switch in the meter box and can then run suitable cable e.g. wire armour internally to the new consumer unit location. That gives you a lot more control over the bulk of the installation/making good within the house.

[jayc89]

Makes sense. So I could run a suitable cable from the under-stair cupboard to a new external meter box (with nothing else in it yet), whilst I'm in the process of ripping rooms apart (so have the access to do so), and then if/when I'm ready to, fit a new CU in the under-stair cupboard, have DNO move the supply cable and fuse into the meter box and have my energy supplier move my meter?

I assume I could also use Henley block in the under-stair cupboard to connect back to the existing CU, if there's a period where I need to continue using the old one? (My sparky generally helps me out evenings/weekends so I'm thinking for the period between the meter being moved by my supplier and him being able to move the connections to the new CU)

 

 

[andyscotland]

In theory I would say yes roughly.

 

The isolator in the meter box needs to be fused.

 

The sub-main cables will almost certainly need to be armoured to avoid the need for RCD protection.

 

You can't use Henley blocks on their own as you can't have cable cores exposed outside an enclosure - they're only ok on the surface with meter tails because those are insulated and sheathed so have mechanical protection.

 

So you'd need to put them in a metal enclosure (which will also allow you to terminate the armour properly) or use an enclosure with DIN rail terminal block rather than Henley which will achieve the same. You could connect that enclosure to the consumer unit with a short length of metal conduit to keep it neat and avoid an extra pair of SWA terminations for the link cable.

 

One thing to watch (especially if extending back to the old CU) will be voltage drop. If you have the full house load on that cable you may need to up-rate it to avoid getting too much of your overall voltage drop allowance before you get to the old CU. It will depend on the design current, cable sizing and length of your existing circuits. The calculations for that can get complex once you start up-sizing cables.

 

Definitely worth running it all by your sparky before committing as ultimately they'll need to sign it off. I'd also keep your own records of cable sizing calculations, photos of the install etc in case time passes and you find yourself working with a different spark down the line.

[jayc89]

Could split concentric cable be used for the sub-mains? I understand it's more flexible than SWA, and I'll have some tight bends to navigate. 

[Mr Punter]

54 minutes ago, jayc89 said:

Could split concentric cable be used for the sub-mains?

 

I have only seen it used for the mains supply up to the cutout.  Sub main in SWA.

[andyscotland]

1 hour ago, jayc89 said:

Could split concentric cable be used for the sub-mains? I understand it's more flexible than SWA, and I'll have some tight bends to navigate. 

 

It's a long time since I trained and we didn't really cover use of split concentric in any depth other than as a supply incomer.

 

I would be pretty sure that it wouldn't have sufficient mechanical protection to avoid the need for an RCD at the origin, which you really want to avoid on a sub-main.

 

The requirements that DNOs work to are different to those for consumer installations.

Edited May 22, 2023 by andyscotland

[jayc89]

I understand the sub-main needs to enter the electric box from either one of two holes on the right hand side; on the bottom or side of the box. Apart from that, are there any regs preventing the SWA going up the outside of the house and entering the property at the height of the first floor void?

[TonyT]

5 hours ago, jayc89 said:

Makes sense. So I could run a suitable cable from the under-stair cupboard to a new external meter box (with nothing else in it yet), whilst I'm in the process of ripping rooms apart (so have the access to do so), and then if/when I'm ready to, fit a new CU in the under-stair cupboard, have DNO move the supply cable and fuse into the meter box and have my energy supplier move my meter?

I assume I could also use Henley block in the under-stair cupboard to connect back to the existing CU, if there's a period where I need to continue using the old one? (My sparky generally helps me out evenings/weekends so I'm thinking for the period between the meter being moved by my supplier and him being able to move the connections to the new CU)

 

 

So after your meter where you have an isolator it needs to be

one of these or similar to let you have your own fuse to protect the cable to the next part of the installation.

 

https://www.tlc-direct.co.uk/Products/CGMSF100.html?source=adwords&ad_position=&ad_id=&placement=&kw=&network=x&matchtype=&ad_type=pla&product_id=CGMSF100&product_partition_id=&campaign=shopping_switchgear_distribution&version=finalurl_v3&gclid=EAIaIQobChMIutK11syJ_wIVG-ztCh2ICQ-dEAQYASABEgInvvD_BwE

 

I’m not a fan of split concentric, generally we used to use them for block of flats when there were risers ti accommodate the extra gear.

[TonyT]

Split concentric does not have an earth all around the conductors so it’s no safer than say a 16mm t&E submain, which would be easier to terminate.( the t&E that is)

 

then it’s 50mm to consider etc, Swa all the way for me.  Easy to gland and terminate 

[andyscotland]

4 hours ago, jayc89 said:

I understand the sub-main needs to enter the electric box from either one of two holes on the right hand side; on the bottom or side of the box. Apart from that, are there any regs preventing the SWA going up the outside of the house and entering the property at the height of the first floor void?

 

Broadly speaking, if cable is clipped direct on the surface it can go anywhere you like. SWA is rated for UV light so can be used externally without any problems.

[jayc89]

11 hours ago, TonyT said:

So after your meter where you have an isolator it needs to be

one of these or similar to let you have your own fuse to protect the cable to the next part of the installation.

 

https://www.tlc-direct.co.uk/Products/CGMSF100.html?source=adwords&ad_position=&ad_id=&placement=&kw=&network=x&matchtype=&ad_type=pla&product_id=CGMSF100&product_partition_id=&campaign=shopping_switchgear_distribution&version=finalurl_v3&gclid=EAIaIQobChMIutK11syJ_wIVG-ztCh2ICQ-dEAQYASABEgInvvD_BwE

 

I’m not a fan of split concentric, generally we used to use them for block of flats when there were risers ti accommodate the extra gear.

Any difference between that type and one of these https://www.directtradesupplies.co.uk/product.php/202439/fusebox-100a-fused-switch--63-80-100a-fuses---white-?gclid=CjwKCAjwpayjBhAnEiwA-7ena6XqoST4qKgfagJeZlUdreiAMRN2nKLLiU6uYCL59tDna5OvKB9ZIxoCcv0QAvD_BwE?

 

I’ve put a cheeky offer in for a length of SWA on eBay, I owe my sparky some beers so that might be this weekends activities sorted out!

[andyscotland]

18 minutes ago, jayc89 said:

Any difference between that type and one of these https://www.directtradesupplies.co.uk/product.php/202439/fusebox-100a-fused-switch--63-80-100a-fuses---white-?gclid=CjwKCAjwpayjBhAnEiwA-7ena6XqoST4qKgfagJeZlUdreiAMRN2nKLLiU6uYCL59tDna5OvKB9ZIxoCcv0QAvD_BwE?

 

That would be fine.

[TonyT]

23 minutes ago, jayc89 said:

Any difference between that type and one of these https://www.directtradesupplies.co.uk/product.php/202439/fusebox-100a-fused-switch--63-80-100a-fuses---white-?gclid=CjwKCAjwpayjBhAnEiwA-7ena6XqoST4qKgfagJeZlUdreiAMRN2nKLLiU6uYCL59tDna5OvKB9ZIxoCcv0QAvD_BwE?

 

I’ve put a cheeky offer in for a length of SWA on eBay, I owe my sparky some beers so that might be this weekends activities sorted out!

It’s a better unit as it allows cables to be glanded into the enclosure. Plus 1 for that product

[SteamyTea]

I thought consumers units had to be at a sensible height now.

Not sure what you had done was legal.

May be wrong.

www.nhbc.co.uk/binaries/content/assets/nhbc/tech-zone/nhbc-standards/tech-guidance/8.1/mounting-height-consumer-units-new-october-2018.pdf

[TonyT]

On new builds maybe. Not a rewire that you don’t have to notify anyone about 

[SteamyTea]

16 minutes ago, TonyT said:

On new builds maybe. Not a rewire that you don’t have to notify anyone about 

Maybe.

I am not sure when replacing and new cross over.

[jayc89]

I was told that rewires don't have to conform to current building regs heights etc, which is why all our light switches haven't been dropped to be accessible either. 

 

The old CU was in the same location. In hindsight, I should have had it moved elsewhere at the time. 

Edited May 23, 2023 by jayc89

[jayc89]

Sparky also used our re-wire as part of his NICEIC assessment (are they annual?), so I'm guessing everything was above board. 

[jayc89]

Gas meter box is bang on where I'd want to install the new electric meter box. What's the min distance I can have between them? I've heard 150mm mentioned anecdotally, but can't find any concrete numbers. 

[TonyT]

Yes it’s 150mm 

 

 

[TonyT]

Page 25 on-site guide for anyone else