Cabling from electricity meter to consumer unit

newparent77

Hi all, I have no idea if this will make sense so please bear with me.

We recently had our electricity meter and consumer unit moved due to knocking through a wall. The meter has moved outside into an external cabinet, and the the consumer unit has been moved onto another wall.

The electrian is now sorting the permanent wiring from the meter outside to the consumer unit inside. He's proposed taking it from the meter, up the back wall, up and along the ceiling of a tunnel that we share with next door to allow access to our back gardens and then into the house from inside the tunnel. I just wanted to sense check though, does that amount of cabling outside seem OK? A lot of it will be under the cover of the tunnel but I wanted to get some views. Bringing it in on the same wall as the meter is a bit complication because there is a boiler between the wall and the consumer unit, and because of kitchen layout, hiding cables etc.

Very crude diagrams to hopefully demonstrate! First is top down, second is looking back at the wall from ground level. Apologies in advance if they don't make sense! Aware that extra precautions need to be taken if the cabling is longer than 3 metres.

chris_n

Most network operators say max 3m long tails. If it is more than this there needs to be some electrical protection. If it is outside it will need mechanical protection too.

tacpot12

As per Chris's note, most Distribtion Network Operators (DNOs) say the "meter tails" as they are called can be no longer than 3m. This means that they need to be terminated into something within 3m of the meter. The something needs to provide the "electrical protection" that Chris referred to; it could be a consumer unit or it could be a fused switch. The electrican can't just run a long cable directly from an unfused isolation switch to a consumer unit that is more than 3m from the meter (measured along the cables). 

The mechanical protection can be earthed metal conduit or provided by Steel Wired Armoured (SWA) cable.

Regardless of whether the electrican choses metal conduit or SWA cable, they will need a fused switch like this one: MCG 100A SP+N Metal Switch Fuse (MCGSFML) | CEF

As a consumer, you don't really need to know the technical details, you just need to specify that the work should comply with the current version of BS7671 and that the electrician is responsible for notifying Building Control. 

   

newparent77

Thank you both, that's really helpful! So just to confirm, the meter tails could eventually be, say, 4m, but in the first 3m of them there needs to be that electrical protection you spoke about? That electrical protection couldn't sit at, say, 3.5m along the cables?

newparent77

And, sorry everyone, but another question. So the consumer unit has been moved by one electrician, involved in some building work we had done which meant it had to be moved. But we also have a second electrician who has done some work for the kitchen company, who will be installing our new kitchen next week.

To be honest, the kitchen electrician is a bit more reliable than the first. As mentioned, the consumer unit needs temp cables replacing with permanent ones - is this something the kitchen electrician could do, even though it was a different electrician who moved and installed the new consumer unit - or does that cause issues with certification etc? 

Sorry if that is complicated!

grumbler

The last electrician can finish the work and certify it.

And my understanding is that you need a fused switch within 3m from the meter. Then cables can go as far as you want from the switch to the CU.

fenwick458

newparent77 said:

Thank you both, that's really helpful! So just to confirm, the meter tails could eventually be, say, 4m, but in the first 3m of them there needs to be that electrical protection you spoke about? That electrical protection couldn't sit at, say, 3.5m along the cables?

the "rule of thumb" is if the tails are any longer than 3 metres they need protection, and protection comes in the way of a fused switch like this
but if you were going to fit one of those the obvious place to fit it would be in the meter cupboard , and then use 16mm SWA (steel wire armoured) cable from the fused switch to the consumer unit

newparent77

Brilliant, thank you, makes sense - I was just thinking if it could be fitted into the meter cupboard itself. Seems the best place to put it if much of the cable is then to be outside.

Thanks again all, really helpful!

Risteard

tacpot12 said:

As per Chris's note, most Distribtion Network Operators (DNOs) say the "meter tails" as they are called can be no longer than 3m. This means that they need to be terminated into something within 3m of the meter. The something needs to provide the "electrical protection" that Chris referred to; it could be a consumer unit or it could be a fused switch. The electrican can't just run a long cable directly from an unfused isolation switch to a consumer unit that is more than 3m from the meter (measured along the cables). 

The mechanical protection can be earthed metal conduit or provided by Steel Wired Armoured (SWA) cable.

Regardless of whether the electrican choses metal conduit or SWA cable, they will need a fused switch like this one: MCG 100A SP+N Metal Switch Fuse (MCGSFML) | CEF

As a consumer, you don't really need to know the technical details, you just need to specify that the work should comply with the current version of BS7671 and that the electrician is responsible for notifying Building Control. 

   

A switch fuse is a very different thing to a fused switch. It's a switch fuse you are referring to.