Can i spur more then once with bigger cable?

[tomodo]

Hi guys working in a factory having to spur off a ring main problem is its already got a fuse spur coming off it for some fans. The ring main is on a 32A breaker and wired in 4mm guessing this might be for volt drop. Question is can i spur off this socket twice using 4mm cable? Then the cabel is protected and safe still. so i can get wires in terminals was thinking to relocate fused spur for fans into new added socket. so it will go RING MAIN spured to new socket then out of there to fused spur. All wired in 4mm. cheers

 

[davesparks]

It is a departure from the standard ring circuit, which doesn't necessarily mean it is wrong but does need a bit more thinking about.

 

[tomodo]

hmmmmm

 

[andyb]

I think HHD is right.
Can you not put the fused spur at beginning of the spur from the ring?

 

[Silly Sausage]

hmmmmm

The FCU is 13A max, so the proposed circuit spur is essentially a triple socket outlet.
I would say it's fine.

(App 15 is 'Informative' only. Other circuit layouts are available!)

 

[shanky887614]

be alot of hassle it goes right up to the ceiling which is about 20 metres high

? cut and joint

 

[Pete999]

The FCU is 13A max, so the proposed circuit spur is essentially a triple socket outlet.
I would say it's fine.

(App 15 is 'Informative' only. Other circuit layouts are available!)

Whereabouts are these other circuit layouts described?

 

[Silly Sausage]

Whereabouts are these other circuit layouts described?

In my brain after applying some thought

 

[Pete999]

In my brain after applying some thought

Yes BS 7671 is an informative document, but if we go on deviating just because we "gave it some thought" and thought we were right and someone got hurt because we thought it was alright, where would we stand in a court of law, "well your honour I thought it would be OK"

 

[Silly Sausage]

'They' are just 'standard' circuits.
Some guys on here have lights on rings or octopus/spider circuits or god help us, Neutrals at the switches!
They are all equally valid. As long they fulfil the Chapter 4 design criteria, all is well in the world!

 

[GEOFF S]

The onsite guide is not for comercial installations.

So im taking a different footing here, the ring circuit design in the onsite guide is for the purpose of a domestic single phase system amongst other prerequisites. So the installed ring is the design of someone? You need to prove it meets the requiremnts of BS7671. Specifically 433.1.103 plus the other general requirements.

Cheers

 

[davesparks]

The onsite guide is not for comercial installations.

So im taking a different footing here, the ring circuit design in the onsite guide is for the purpose of a domestic single phase system amongst other prerequisites. So the installed ring is the design of someone? You need to prove it meets the requiremnts of BS7671. Specifically 433.1.103 plus the other general requirements.

Cheers

I thought we were talking about the ring circuit design in bs7671 not the idiots guide?

 

[GEOFF S]

I thought we were talking about the ring circuit design in bs7671 not the idiots guide?

Where is this ring design?

Cheers

 

[davesparks]

Where is this ring design?

Cheers

Read the whole thread, the answer is in post 2, appendix 15.

 

[GEOFF S]

Read the whole thread, the answer is in post 2, appendix 15.

Dave, thats not a ring circuit design, its sets out the special regulation 433.1.103, that asisde its down to the deisgner to meet all the other general requirements.

Cheers

 

[davesparks]

Dave, thats not a ring circuit design, its sets out the special regulation 433.1.103, that asisde its down to the deisgner to meet all the other general requirements.

Cheers

I've not got the book in front of me but I thought that was where there is a full page illustration of the standard ring final circuit with spurs etc clearly illustrated.

 

[GEOFF S]

I've not got the book in front of me but I thought that was where there is a full page illustration of the standard ring final circuit with spurs etc clearly illustrated.

Yes it shows you a typical arrangement, no design spec. The standard circuits in the onsite guide have prerequsites set out, if these are not met then you need to design the circuit and show compliance.

Cheers

 

[Charlie_]

Also that little diagram is based on the ring being wired in 2.5.
In this case as initially explained the ring is wired in 4mm with a proposed 4mm spur

 

[shanky887614]

i wouldn't just guess its 4mm based on vd.

we were laughing at the way overspeced supplies on some jobs.

they were told your not allowed to use anything smaller than 4mm XD

it was for little smoke damper boxes controlling an individual smoke damper.

another personal favorite was a 70mm supply to a panel that only had 50a isolator

 

[davesparks]

Also that little diagram is based on the ring being wired in 2.5.
In this case as initially explained the ring is wired in 4mm with a proposed 4mm spur

Without further information we have to assume a worst case scenario that 4mm has been used due to de-rating factors making the ccc of 2.5mm too low for a ring. So without further information we cannot assume that the 4mm when de-rated has only got the ccc of the 2.5 in the standard circuit.