Spur Cable Sizing

[buzzbuzz]

Hi

I'm adding a fused spur (6A) to a 32A ring to power a central heating boiler. Does the spur cable have to be the same CSA as the ring (2.5mm) or can I reduce the cable size to be minimum size required for load on that spur ? Also, is it then treated as a radial circuit for sizing/speccing etc?

Buzz

 

[NEsparky]

I assume you are fitting a fused spur for the boiler, if so it is possible that someone will change the fuse from a 5 amp to a 13.

As im sure you have already worked out this therefore means at least 2.5

Hope this helps

 

[buzzbuzz]

NEsparky

Thanks......I realised this just after typing the question. I was having a dumb moment I reckon...trying to reduce cost of materials without realising the possible consequences.

Buzz

 

[Hawk81]

I assume you are fitting a fused spur for the boiler, if so it is possible that someone will change the fuse from a 5 amp to a 13.

As im sure you have already worked out this therefore means at least 2.5

Hope this helps

I would disagree. do you wire everything from a spur in 2.5mm? lights ect. bet you don't. label the spur max 5amp fuse.

 

[biggrilla]

Looking at appendix 15 of BS7671 shows that if you connect a fcu you can only downsize the cable on the output side of the spur - has to be 2.5 on the supply side.

All the best

BigGrilla

 

[NEsparky]

Tend not to run light of a spur me being an electrician and all!!!!!

Would not wire boiler in 2.5 would use 1.5 HR which would be capable of taking 13 amps.

Also if in future if that spur is to be used for a different applience that has a higher raiting it means the same job has to be completly redone for what the diffence of a couple of quid now?

Sorry pall if thats your view, your not looking at the full picture.

 

[Hawk81]

Tend not to run light of a spur me being an electrician and all!!!!!

Would not wire boiler in 2.5 would use 1.5 HR which would be capable of taking 13 amps.

Also if in future if that spur is to be used for a different applience that has a higher raiting it means the same job has to be completly redone for what the diffence of a couple of quid now?

Sorry pall if thats your view, your not looking at the full picture.

Hold on a minuite PAL. firstly what do you mean you would not wire a light from a spur because you are an electrician?? think you will find there is nothing wrong with it. a lot of electricians on this forum have done it at some point. my point was that the output cable from the spur does not have to be 2.5mm and i am right. the supply cable would need to be 2.5mm.

 

[NEsparky]

Yea your correct, but we were not disscusing the load side, rather the supply if you read again you will realise this.

Spur to light is cheap easy fix, I would suggest its better to run lights of a lighting circuit?

Well in my world any way!

 

[Welshsparky]

You were not talking about the supply, you were blatenly talking about the load side.

 

[nickblake]

Yes hawks your right ,and i agree , if you have a fused spur obviousley you have to wire the incomming side in 2.5 mm but the out put of the fused spur can be wired in 1.5mm as it will be protected by a 13 amp fuse and doing this you can also wire sockets in 1.5 mm twe as long as its protected by the 13 amp fuse of the fused spur and its in the regs try appendix 15 , page 362

 

[NEsparky]

WELSH SPARKY Yawn!!!!!!! Question and my first post it is plainly descussing the supply side i suggest you read it again.

To be honest mate what did it have to do with you?

The guy that posted the question understood what i ment anyway aslong as he is happy!!!!!!!!!!!!!!

 

[Hawk81]

WELSH SPARKY Yawn!!!!!!! Question and my first post it is plainly descussing the supply side i suggest you read it again.

To be honest mate what did it have to do with you?

The guy that posted the question understood what i ment anyway aslong as he is happy!!!!!!!!!!!!!!

you have some attitude

 

[NEsparky]

Its a skill! Took years to perfect!

If you try hard you will get to like it.

 

[chiplard]

People with attitude in my experience tend not to know what they are talking about and have an attitude to cover this up!!!!

The OP asked a very simple question that was answered correctly by other posters. There was never any need to start preaching about what should and shouldn't be done as a sparky. Everybody has different ways of doing things but as long as they comply with the BRB then there is no issue.

 

[eskimo39]

Yea your correct, but we were not disscusing the load side, rather the supply if you read again you will realise this.

Spur to light is cheap easy fix, I would suggest its better to run lights of a lighting circuit?

Well in my world any way!

Hi mate, not trying to cause an argument here but in many years of work I have occasionally found a customer who wants an outside light but is not prepared to let me chase cables into walls or run conduit outside. Therefore by adding a spur from an upstairs socket I can drill out of the back to the outside and straight into a controlled floodlight etc. This isn't a cheap easy fix as you put it, it is sometimes the only option. In an ideal world I would love to be able to cut chases wherever I like and do every job in the best way, however in a real life situation I often find there are many things that mean I have to find alternative method of installation.

Regards