Wiring for garden office - can I spur off an external socket?

[thatsimpsongirl]

Hi,

I’m not an electrician so seeking advice as to whether my requests were actions correctly or if I need to arrange for additional / remedial work to be done.

During the first fix of a renovation I told the electricians working on my project that I planned to put an office / studio in the garden at a later date & could they run something outside that would be suitable. They told me that they’d install an external socket and that any connection could be spurred off that for an office constructed at a later date.

I am now in the process of getting quotes for the studio and not sure if the external socket will be enough? The renovation isn’t quite finished so although it would be a real pain to run another cable from the fuse box it would be easier to do it now rather than later.

I attach pictures of the cables that are running to the outside as well as the external socket (this one OA036AG) . We would be planning to have a couple of 230v sockets (charging laptops etc) and some lights.

Would be grateful for any advice,

Nikki

 

[loz2754]

What did W10 SAY then can't see his response.

Post number 5 I think Pete.

 

[brianmoooore]

Very roughly, what is the distance from the external socket to the new studio?

 

[thatsimpsongirl]

Very roughly, what is the distance from the external socket to the new studio?

About 5m. So not too far.

 

[brianmoooore]

In that case, a 32A supply to your studio should be possible. Go on from the outside socket with 4.0mm2 or 6.0mm2 3C SWA to a small non RCD consumer unit in your studio.
Only downside, is that the RCD for the studio will be indoors on the main CU, so if it trips you will lose all power to the studio, including lights, and you will have to go indoors to reset it.

 

[Pete999]

In that case, a 32A supply to your studio should be possible. Go on from the outside socket with 4.0mm2 or 6.0mm2 3C SWA to a small non RCD consumer unit in your studio.
Only downside, is that the RCD for the studio will be indoors on the main CU, so if it trips you will lose all power to the studio, including lights, and you will have to go indoors to reset it.

I'm surprised Brian that you would condone changing the size of the cable at the point of connection to the outside socket, not one person has asked if this outside socket is a spur or whether it is part of an RFC, apart from myself post 6, sorry for the disagreement to your reply.

 

[loz2754]

Hi Pete. I believe the OP has stated that the socket is fed directly on its own 32 amp MCB in the consumer unit.

 

[Pete999]

Hi Pete. I believe the OP has stated that the socket is fed directly on its own 32 amp MCB in the consumer unit.

 

[Pete999]

Right thanks for that must have missed that,

 

[brianmoooore]

It's not been verified that the existing outside socket is the only connection to a 32A MCB, wired in 4.0 or 6.0mm2 T&E, but the signs are promising. My last post does depend on this being true, of course.

 

[pc1966]

If, as it appears to be, it has a dedicated 32A MCB feeding it then it should be at least 4mm cable and plenty capable of feeding the garden office. When all of the current work is done the completion certificate should confirm that, along with various other measurements that would allow the correct design of the office electrics.

The only possible issue is what @brianmoooore pointed out - the RCD protection is in the house's main CU (fuse box) and shared with other circuits. Not normally a problem, but an extra inconvenience if a fault does develop (compared to separate RCD).

For sockets and lights in a small office style arrangement you almost don't need a 2nd CU in the out building as the lights could come off a FCU (fused connection unit), but for all the cost of a CU it provides a handy place to isolate and test circuits, even if the MCBs in it have little selectivity with the feed from the house.

 

[thatsimpsongirl]

Thanks @pc1966 and @brianmoooore - and thanks in general to everyone for all the replies, I didn't expect to receive so much good advice in such a short space of time!

I note your points re the cable size / whether there are any other connections to the 32A MCB / RCD protection (annoying but not insurmountable). The completion cert is not yet done as there are a few things still to be connected up (kitchen appliances etc.) but will show this to whoever does the work outside once I receive it.

Obviously I will be getting a qualified professional for all the studio electrics but it does seem to make a difference in how seriously I am taken on site if I'm well informed (at least as far as I can be as a non-specialist). Just wish one of you guys had been my electricians in the first place!

Thanks again

Nikki ?