Spur off 32a house socket form garage for 20a supply.

[Johnconnor]

Hi, if getting back to the CU is not an option, instead of spurring off a socket via a Sfs putting the rating down to 13a. Could you spur off the socket and take it down to 20a or 16a instead via a submain to allow for that extra kW if needed. If the cable size was sufficient for the length. For a garage sub main wired in swa. (32a ring circuit). In theory if you had sockets on a 16a rcbo and lights on a 6a then it's under the 27A limit generally a 2.5 can take. Thanks

 

[westward10]

Might help if you actually stated what you are trying to achieve as apposed to random disjointed bullet points.

 

[Johnconnor]

Might help if you actually stated what you are trying to achieve as apposed to random disjointe

 

[Johnconnor]

Apologies. My mission is to achieve a bigger supply to a garage of 16 to 20amps, rather than 13a. I'm not trying to achieve anything physically, I just want to know if it's possible, forgetting about what the spec is for the job. Is it allowed?

 

[mainline]

Apologies. My mission is to achieve a bigger supply to a garage of 16 to 20amps, rather than 13a. I'm not trying to achieve anything physically, I just want to know if it's possible, forgetting about what the spec is for the job. Is it allowed?

Yes you could

 

[nicebutdim]

Yes you could

Care to explain your reasoning?

You're stating that a 'submain' which is 'spurred' off a ring final circuit, protected by a device that'll happily permit in excess of 27A for hours on end is permitted.

The IET are clear about what is permitted to be spurred of this type of circuit and they don't include 'submain protected by 16A or 20A device'.

Maybe the OP will proceed on the basis of 'some person on the internet said it was okay', but I'd advise against doing so and point out that their proposal isn't permitted on a regulatory basis and is also flawed on a theoretical level.

 

[Rockingit]

Care to explain your reasoning?

You're stating that a 'submain' which is 'spurred' off a ring final circuit, protected by a device that'll happily permit in excess of 27A for hours on end is permitted.

The IET are clear about what is permitted to be spurred of this type of circuit and they don't include 'submain protected by 16A or 20A device'.

Maybe the OP will proceed on the basis of 'some person on the internet said it was okay', but I'd advise against doing so and point out that their proposal isn't permitted on a regulatory basis and is also flawed on a theoretical level.

You are only allowed to supply equipment to BS1363 via a spur from a ring final circuit (433.1.204). As that standard (to the best of my knowledge, anyway) does not contain devices rated to greater than 13A then it's mechanically impossible to exceed the 13A barrier.

 

[nicebutdim]

You are only allowed to supply equipment to BS1363 via a spur from a ring final circuit (433.1.204). As that standard (to the best of my knowledge, anyway) does not contain devices rated to greater than 13A then it's mechanically impossible to exceed the 13A barrier.

OP is asking if instead of using a 13A fcu they could spur using a 16A or 20A device as a 'submain' to supply a garage.

"instead of spurring off a socket via a Sfs putting the rating down to 13a. Could you spur off the socket and take it down to 20a or 16a instead via a submain to allow for that extra kW if needed"

"My mission is to achieve a bigger supply to a garage of 16 to 20amps, rather than 13A"

Their proposal omits 13A protection mandated by the wiring regulations in such instances.

The omission of 13A protection is clear in their first sentence, with everything else clarified in their follow up post.

This proposal would not be permitted and for good reason.

 

[Rockingit]

OP is asking if instead of using a 13A fcu they could spur using a 16A or 20A device as a 'submain' to supply a garage.

"instead of spurring off a socket via a Sfs putting the rating down to 13a. Could you spur off the socket and take it down to 20a or 16a instead via a submain to allow for that extra kW if needed"

"My mission is to achieve a bigger supply to a garage of 16 to 20amps, rather than 13A"

Their proposal omits 13A protection mandated by the wiring regulations in such instances.

The omission of 13A protection is clear in their first sentence, with everything else clarified in their follow up post.

This proposal would not be permitted and for good reason.

We're on the same page here matey, my (possibly poorly worded) post was basically saying that you can only hang BS1363 (eg a 13A fused spur) rated equipment off a RFC. To use a 16A or 20A device to protect the 'sub main' would be by it's very nature a different BS standard - either 3036, 60898, 61009..... etc and therefore not comply.

And that's before we get to discussion about whether it's a good idea or not!! (Hint: It's not).

 

[nicebutdim]

We're on the same page here matey, my (possibly poorly worded) post was basically saying that you can only hang BS1363 (eg a 13A fused spur) rated equipment off a RFC. To use a 16A or 20A device to protect the 'sub main' would be by it's very nature a different BS standard - either 3036, 60898, 61009..... etc and therefore not comply.

And that's before we get to discussion about whether it's a good idea or not!! (Hint: It's not).

Problem with threads like this is OP has been told it's fine and hasn't been back since.

They're quite possibly in screwfix buying a small din rail enclosure and 20A MCB.

 

[Pretty Mouth]

I agree with @Rockingit 's post regarding rings and BS1363 accessories, from a compliance point of view.

However... the arrangement where a garage is spurred from a ring final, via an 13A FCU, is not ideal in practice. I have had to deal with a few burnt out FCUs where it has been installed this way. Real world, they don't seem to be reliably up to the job.

IMO, while technically not compliant, it would actually be an improvement to protect the spur to the garage with a 16A breaker instead of an FCU. They are more reliable, and the time/current curve is very similar to a 13A BS1362 fuse anyway.

The lighting could likely be protected by the same device, without further fusing down, or the 6A breaker could be wired downstream of the 16A one.

 

[Rockingit]

I agree with @Rockingit 's post regarding rings and BS1363 accessories, from a compliance point of view.

However... the arrangement where a garage is spurred from a ring final, via an 13A FCU, is not ideal in practice. I have had to deal with a few burnt out FCUs where it has been installed this way. Real world, they don't seem to be reliably up to the job.

IMO, while technically not compliant, it would actually be an improvement to protect the spur to the garage with a 16A breaker instead of an FCU. They are more reliable, and the time/current curve is very similar to a 13A BS1362 fuse anyway.

The lighting could likely be protected by the same device, without further fusing down, or the 6A breaker could be wired downstream of the 16A one.

Whether we have a different approach from an engineering perspective or not, I think we can all agree that this forum should only, ever, give advice which is compliant.

 

[davesparks]

Could you spur off the socket and take it down to 20a or 16a instead via a submain to allow for that extra kW if needed.

No, you can't take a distribution circuit (submain) from a final circuit.

 

[Pretty Mouth]

Whether we have a different approach from an engineering perspective or not, I think we can all agree that this forum should only, ever, give advice which is compliant.

The IET doesn't seem to agree with that sentiment, and suggest connecting equipment via a 16A breaker in the OSG. This is from appendix H, P211:

Permanently connected equipment should be locally protected by a fuse complying with BS 1362 of rating not exceeding 13 A or by a circuit-breaker of rating not exceeding 16 A and should be controlled by a switch, where needed (see Appendix J).

 

[mainline]

No, you can't take a distribution circuit (submain) from a final circuit.

What's wrong with extending the ring to the outbuilding.