UK Supply to 2 outbuildings

[DrDunbar]

Hi. I have a shed with its own small consumer unit connected by underground SWA to a connection box on the outside wall of the house. This in turn is wired to ts own MCB in the consumer unit of the house. I am going to erect another outbuilding some distance away from the shed. SWA for this was laid a couple of years ago (size was per recommendation of a qualified electrician). I plan to install a small consumer unit also in the new outbuilding. My question is: Can I connect the new SWA cable to the same outside connection box along with the existing shed or do I need to wire separately into the house consumer unit via a separate MCB?

 

[davesparks]

It's impossible to say without knowing the details of the existing circuit, the details of the new cable and the intended use/loading on the circuit.

 

[Dustydazzler]

this needs to be designed and installed correctly

you have volt drop to consider and how much load you plan on using

the existing circuit might be for example on a 16amp circuit which might need upgrading etc etc

 

[timhoward]

Stating the size of the MCB in the house would be a good start to working this one out.
As both replies above say, the intended usage of the sheds is crucial.
But in addition, installing a consumer unit (even in an outbuilding) is notifiable to LABC.
Best to get the electrician who recommended the cable size back to connect up - it won’t be a big job by the sound of it.

 

[DrDunbar]

Thanks for responses so far. The existing shed is connected to main CU via a 32B MCB. The Shed CU serves 2 sockets and a light. Load is very light almost never above 1KW. The new outbuilding will have an almost identical circuit layout and anticipated load. It was acquired a few years ago but I think the "new" SWA is 25mm2.

 

[davesparks]

Are you sure it's 25mm and not 2.5mm?

If its 25mm then it will be physically too big to connect in to the existing joint in the 32A circuit. However an electrician would be able to replace the joint and make a safe connection.

If it is 2.5mm then it is too small to be protected by a 32A MCB and so cannot be connected in to that circuit.

 

[timhoward]

It’s been known for customers to quote the outside diameter of the entire cable.

 

[DrDunbar]

Are you sure it's 25mm and not 2.5mm?

If its 25mm then it will be physically too big to connect in to the existing joint in the 32A circuit. However an electrician would be able to replace the joint and make a safe connection.

If it is 2.5mm then it is too small to be protected by a 32A MCB and so cannot be connected in to that circuit.

Both outbuildings are some distance from the house and the SWA looks similar for both. Yes, they are physically large and I suspect that's why the existing shed is connected in the way it is. The existing SWA is connected to the MCB via a smaller cable connected in the external junction box. This smaller cable could be 6mm2 as its external appearence is similar to the cooker supply. I was wondering whether the new SWA can utilise this same external connection.

 

[davesparks]

Both outbuildings are some distance from the house and the SWA looks similar for both. Yes, they are physically large and I suspect that's why the existing shed is connected in the way it is. The existing SWA is connected to the MCB via a smaller cable connected in the external junction box. This smaller cable could be 6mm2 as its external appearence is similar to the cooker supply. I was wondering whether the new SWA can utilise this same external connection.

Post up a picture of the existing connection, inside and out, and the cable.

We might be able to advise based on that

 

[Markyd]

The installation will need signing off and a cert issued....You need a sparky not Advice