fused spur cable length???

[scott.rick]

i recently had to add a spur from a ring to supply a item of fixed equipment. I took the supply from a socket into to a switched fused spur and placed the necessary fuse for the equipment directly after the socket then a 10 meter cable run to a flex outlet connection unit then a 0.5m flex cord on the item of equipment.

My QS now tells me that the run is only allowed to be a maximum of 2 meters or else the spur must be changed to a ring and the socket i took the feed from must be re-configured to allow this. He claims this is stated in the regs but i have never heard of this?? i have always thought that provided the voltage drop is not too much and the resistance is within the max zs for the protective device etc then this is acceptable.

has anyone else come across this or if its in the regs can you tell me where it is please??

 

[JulianC]

I've never come across it in the regs. either. As you say, as long as volt drop and Zs are within limits, I don't see what the problem is.

 

[davelerave]

i'd say the 13a spur should preferably connect directly to the appliance 'power cord'

maybe he's referring to 2m distance for isolation of the appliance?

 

[simonspark]

I think your QS should go back to JI

 

[ezzzekiel]

something to do with half length of ring cant remember but its there somewhere

 

[simonspark]

OOps. Unless the item is a requires alocal means of isolation. But even so, you do not have to reconfigure to keep it on the ring

 

[pennywise]

Maybe it's to do with spuring off a spur. If the guy wants the means of isolation within 2m, the current spur would count as the single spur off the ring the new position would be the second, probably wrong. Think the QS just wants the means of isolation closer.

Having looked again think he does want you to make the first fused spur you put in part of the ring and the second closer flex outlet the spur from the ring and replace the plate with a switched fuse spur.

 

[simonspark]

If you look at the back of the 17th, they have all kinds of nice little drawings regarding radials, ringgs and spurs. Spider sysstems are now officially ok and you can wire sockets in 1.5 twin and earth. Nothing about max length of run for a spur in relayion to the lenghth of a ring final circuit though

 

[scott.rick]

he cant mean he wants a means of isolation closer to the fixed equipment as the switch is only 0.5m from it?

does this mean that nobody has ever heard of a min / max cable length for a spur i spoke to a few people who are currently teaching the regs and they have not come across it.

also its not a 13amp spur as its supplying an item of equipment requiring only a 2 amp fuse i have come from the socket into the switched fused spur containing a 2amp fuse then out of that in 1.5mm t&e cable.

 

[davelerave]

i don't think long runs of cable from spurs is a great idea myself

i think the spur should be close to the appliance


if long runs were allowed you could have wiring all over the place going back to spurs

 

[Sintra]

Lengths of unfused spurs off a ring final circuit should not generally exceed 1/8 the cable length from the spur to the furthest part of the ring. OSG p54

This is what i can find on the subject but this is for an unfused spur.

 

[Sintra]

he cant mean he wants a means of isolation closer to the fixed equipment as the switch is only 0.5m from it?

does this mean that nobody has ever heard of a min / max cable length for a spur i spoke to a few people who are currently teaching the regs and they have not come across it.

also its not a 13amp spur as its supplying an item of equipment requiring only a 2 amp fuse i have come from the socket into the switched fused spur containing a 2amp fuse then out of that in 1.5mm t&e cable.

It is a flex connection unit that is 0.5M away not a switch.

 

[scott.rick]

its not an unfused spur tho its a switched fused spur off a ring and that is different plus the regs only say max number of outlets spured off a ring unfused, isnt it that if its fused you cant put as many as you like as long as it doesnt exceed total fo that cable and protection???

 

[scott.rick]

It is a flex connection unit that is 0.5M away not a switch.

its a switched connection unit!!

 

[Sintra]

Then i see no problems.

 

[scott.rick]

whe i get the chance to quiz him about it and if he gives me the place he got this idea from i will let everyone know!!!

 

[scott.rick]

this is where he got the conclusion

BS7671 page 74

433.2.2 The device protecting a conductor against overload may be installed along the run of that conductor in the part of the run between the point where a change occurs ( in cross-sectional area, method of installation, type of cable or conductor, or in environmental conditions ) and the position of the protective device has neither branch circuits nor outlets for connection of current-using equipment and fulfills at least one of the following conditions:

(i) It is protected against fault current in accordance with the requirements stated in Section 434
(ii) It's length does not exceed 3 m, it is installed in such a manner as to reduce the risk of fault to a minimum, and it is installed in such a manner as to reduce to a minimum the risk of fire or danger to persons ( see also Regulation 434.2.1 )

im still unsure if my installation is wrong and i have to rewire it or not????

 

[JamesBrownLive]

this is where he got the conclusion

BS7671 page 74

433.2.2 The device protecting a conductor against overload may be installed along the run of that conductor in the part of the run between the point where a change occurs ( in cross-sectional area, method of installation, type of cable or conductor, or in environmental conditions ) and the position of the protective device has neither branch circuits nor outlets for connection of current-using equipment and fulfills at least one of the following conditions:

(i) It is protected against fault current in accordance with the requirements stated in Section 434
(ii) It's length does not exceed 3 m, it is installed in such a manner as to reduce the risk of fault to a minimum, and it is installed in such a manner as to reduce to a minimum the risk of fire or danger to persons ( see also Regulation 434.2.1 )

im still unsure if my installation is wrong and i have to rewire it or not????

Ok, I'm going out on a limb here but.....

The above quoted part of the regs seems to pertain to installing a protective device after a point where a change ( in cross-sectional area, method of installation, type of cable or conductor, or in environmental conditions ) has been made, as opposed to the standard requirement of 433.2.1 that states the protective device must be installed at the point of the change.

With that in mind, if no changes ( in cross-sectional area, method of installation, type of cable or conductor, or in environmental conditions ) have been made before the spur cable reaches the existing FCU, is this particular reg even applicable?

If you replaced the switched flex unit with a combined SFU/FCU as long as the cable connecting that back to the ring, was not subject to any of the changes already mentioned, then surely this would resolve the issue?

I'm probably wrong though and no doubt someone will tell me why.

 

[martysparky]

Maybe it's to do with spuring off a spur. If the guy wants the means of isolation within 2m, the current spur would count as the single spur off the ring the new position would be the second, probably wrong. Think the QS just wants the means of isolation closer.

Having looked again think he does want you to make the first fused spur you put in part of the ring and the second closer flex outlet the spur from the ring and replace the plate with a switched fuse spur.

please can you post any regs regarding spur from spur. would be much appreciated.

Can you spur off the ring for sockets on radial via a FCU then supply some down lights off the same radial if the total does not exceed 13A.

 

[pennywise]

please can you post any regs regarding spur from spur. would be much appreciated.

Can you spur off the ring for sockets on radial via a FCU then supply some down lights off the same radial if the total does not exceed 13A.

Have a look in appendix 15 might be something in there haven't got the BRB to hand, don't take it to bed with me.

You can spur from the ring, then spur from the load side of the 13amp fused spur or one of the additional sockets feed from the first fuse spur, then spur to another switched fuse spur for a lighting circuit fused to 5 amps. christ thats a lot of fused bits getting myself confused