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

 

[davesparks]

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

Nothing, and I didn't say anything was.

What I said was that you cannot take a distribution circuit (aka submain) from a final circuit.
If you extend a final circuit into another building then it is still a final circuit.

 

[mainline]

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.

Any single point of the ring final could do the same at a double socket outlet.

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'.

To be accurate, while the regs no longer offer it as a 'deemed to comply' solution, that's still a long way from being a non-standard (as in doesn't comply with BS 7671) installation. I think the worst you can say is non-conventional. Much of the "rules" for ring circuits have been taken out from the normative parts BS 7671 over the years and now only exist as general guidance. It's likely a 16A MCB fed from as ring could still comply with all of BS 7671's requirements

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.

My reply to the OP was in relation to :

Johnconnor said: 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?

The OP asked if it was possible, and also stated that he wasn't going to do anything physical.

 

[westward10]

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).

I pretty sure this was at one point in the Regs I'm not going to hunt for it but it rings a bell.

 

[mainline]

Nothing, and I didn't say anything was.

What I said was that you cannot take a distribution circuit (aka submain) from a final circuit.
If you extend a final circuit into another building then it is still a final circuit.

What would be wrong with a say a 6mm radial ?

 

[nicebutdim]

Any single point of the ring final could do the same at a double socket outlet.

To be accurate, while the regs no longer offer it as a 'deemed to comply' solution, that's still a long way from being a non-standard (as in doesn't comply with BS 7671) installation. I think the worst you can say is non-conventional. Much of the "rules" for ring circuits have been taken out from the normative parts BS 7671 over the years and now only exist as general guidance. It's likely a 16A MCB fed from as ring could still comply with all of BS 7671's requirements


My reply to the OP was in relation to :

Johnconnor said: 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?

The OP asked if it was possible, and also stated that he wasn't going to do anything physical.

The OP asked if he was "allowed" to take use 16A or 20A protection from an unspecified device to give himself an extra 3kW on a garage supply. The OP stated that their intention was to do so by "spurring" this unspecified protective device off a ring final circuit in place of a fcu. Her went on to clarify that this would supply 16A & 6A RCBOs in the garage.

You responded by stating that "he could".

These are the facts and let's not dress it up by claiming any information beyond that posted.

The advice wasn't in line with regulatory requirements and has the potential for loads considerably above that permitted to be carried by the cable intended for use if 20A protection is used at the proposed 'spur'.

Edit: I'm not the forum police and you're free to post as you please. On this occasion I believe the advice to be inappropriate and challenged it.

 

[MDJ]

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

nothing else to say, this is the answer, end of

 

[loz2754]

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).

Note that this refers to permanently connected equipment (for which the load would be known and fixed). This would not allow for connecting socket outlets or another consumer unit, for which the load is obviously not known nor fixed.

Of course, this appendix is dealing with standard (formerly known as conventional) final circuits.
There is nothing to stop a competent designer from doing whatever they want, as long they note it as a deviation on the certification, and declare that it is no less safe than it would be if the design was done strictly to BS7671.

 

[mainline]

Permanently connected equipment may be connected directly to a ring final circuit using a fused connection unit incorporating a BS 1362 fuse (not exceeding 13 A) or a Type B or C circuit-breaker (not exceeding 16 A) complying with BS EN 60898 or BS EN 61009-1, or BS EN 60947-2. In the case of some existing installations, Type 1, 2 or 3 MCBs complying with BS 3871 may still be encountered.

 

[mainline]

The OP asked if he was "allowed" to take use 16A or 20A protection from an unspecified device to give himself an extra 3kW on a garage supply. The OP stated that their intention was to do so by "spurring" this unspecified protective device off a ring final circuit in place of a fcu. Her went on to clarify that this would supply 16A & 6A RCBOs in the garage.

You responded by stating that "he could".

These are the facts and let's not dress it up by claiming any information beyond that posted.

The advice wasn't in line with regulatory requirements and has the potential for loads considerably above that permitted to be carried by the cable intended for use if 20A protection is used at the proposed 'spur'.

Edit: I'm not the forum police and you're free to post as you please. On this occasion I believe the advice to be inappropriate and challenged it.

@westward10 asked him to clarify as to what he was actually wanting my answer was in response to the Ops post hence is why I quoted the Ops post in my one with yes he can.

 

[mainline]

Note that this refers to permanently connected equipment (for which the load would be known and fixed). This would not allow for connecting socket outlets or another consumer unit, for which the load is obviously not known nor fixed.

Of course, this appendix is dealing with standard (formerly known as conventional) final circuits.
There is nothing to stop a competent designer from doing whatever they want, as long they note it as a deviation on the certification, and declare that it is no less safe than it would be if the design was done strictly to BS7671.

The max load of the entire circuit is still governed by the 32amp breaker.

 

[nicebutdim]

@westward10 asked him to clarify as to what he was actually wanting my answer was in response to the Ops post hence is why I quoted the Ops post in my one with yes he can.

I know and it was this I challenged. Nothing has yet supported your position that the proposed '16A or 20A spur' is acceptable.

 

[nicebutdim]

The max load of the entire circuit is still governed by the 32amp breaker.

Governed to what level of overcurrent?

A downstream type B 20A mcb could allow more than 32A for a considerable period of time on the proposed spur, without tripping. Not sure 32A protection at source is going to do much.

 

[mainline]

Governed to what level of overcurrent?

A downstream type B 20A mcb could allow more than 32A for a considerable period of time on the proposed spur, without tripping. Not sure 32A protection at source is going to do much.

How different would it be if the ring was extended, which I assume you would agree was ok ?

A double socket outlet could have a 26 amp load, but one that has 16amp load would be too much ?

 

[Pretty Mouth]

Note that this refers to permanently connected equipment (for which the load would be known and fixed). This would not allow for connecting socket outlets or another consumer unit, for which the load is obviously not known nor fixed.

Of course, this appendix is dealing with standard (formerly known as conventional) final circuits.
There is nothing to stop a competent designer from doing whatever they want, as long they note it as a deviation on the certification, and declare that it is no less safe than it would be if the design was done strictly to BS7671.

It refers to permanently connected equipment, not specifically permanently connected current-using equipment.

Electrical equipment (abbr: Equipment). Any item for such purposes as generation, conversion, transmission, distribution or utilization of electrical energy, such as machines, transformers, apparatus, measuring instruments, protective devices, wiring systems, accessories, appliances and luminaires.

Current-using equipment. Equipment which converts electrical energy into another form of energy, such as light, heat or motive power.

 

[nicebutdim]

How different would it be if the ring was extended, which I assume you would agree was ok ?

A double socket outlet could have a 26 amp load, but one that has 16amp load would be too much ?

Again that's not in line with OP's proposal of 16A or 20A protection.

You're here in your capacity as an electrician providing advice. What might or might not be okay is of less relevance than what regulations permit.

People often come here and listen only to points which suit their thinking. As such I'm of the opinion that advice to DIY members shouldn't play fast and loose with regulations. On this occasion the OP declined the opportunity to provide any information about experience or qualifications, so should be treated as being entirely without either.