Spur of Ring

[m4tty]

Hi,

Scenerio.

Spur off ring mains by cutting in to leg, put in Junction box (accessible), then cable run to switched FCU for bathroom extractor switch (all outside bathroom).

Does the cable need to be 2.5mm to the FCU from JB or is 1/1.5mm ok as extractor not going to draw hardly anything.

Thanks for any replies if you can understand my bad explanation.

 

[Brian 157]

If the cable is fused down (protected by the fuse in the spur unit) it should be ok to use 1.5/1.0mm on the outgoing side, you could argue "back protection" for the cable feeding the spur but it would be better to use 2.5mm.

 

[Andy™]

shouldnt really be a problem using 1.5 unless its a long run. the 32A will give fault protection. 1mm would probably be enough, but id stick to 1.5 as a minimum

 

[sellers]

Personally, I would use 2.5 to feed the spur, what happens if at a later date the spur is changed to a single socket or even a double. For the sake of a little bit of cable I'd stick with 2.5mm.

 

[Andy™]

even if its changed, 1.5 should be fine since the max load is still 13A, same as your spur. personally, id use 2.5, or maybe 1.5 for something like a fan or light

 

[sellers]

With it being an unfused spur you would be relying on the 32A mcb to trip before the 1.5mm melts (which it wouldn't). If at a later date the spur was changed to a double socket, then you could get 26Amps flowing down the 1.5. MCB doesnt trip, cable gets very hot.

I didn't think you could spur off a 2.5 ring in anything less than 2.5 unless fused?

 

[ian932]

Personally, I would use 2.5 to feed the spur, what happens if at a later date the spur is changed to a single socket or even a double. For the sake of a little bit of cable I'd stick with 2.5mm.

I agree if someone changes this to double gang skt down the line its not up to the job, stick 2.5mm in and you sleep well.

 

[Andy™]

all accessories (fused spurs, single sockets and double sockets etc) are all 13A max. this is all thats required to comply with BS1363.

 

[ian932]

Andy you and I know that but the general public don't and will not think twice about putting 2x13A bits of kit or multi adapters in a double. I'd rather the skt melt than cable running through combustible materials.

 

[Andy™]

Andy you and I know that but the general public don't and will not think twice about putting 2x13A bits of kit or multi adapters in a double. I'd rather the skt melt than cable running through combustible materials.

general public are thick! try and warn them, but they always know better! except when they have to get burnt out sockets replaced because they dont know what they are doing

 

[ian932]

Looking at the OP he is saying its connected to the ring via a JB so it has to be 2.5mm, the only way he can do it with 1.5mm is if he connects the FCU into the ring, BRB page 362

 

[tom1]

do thay do 27 amp sockets

 

[Andy™]

do thay do 27 amp sockets

no. closest you will get to that is a 32A BS4343 (cant remember EN number) socket

 

[sellers]

Double sockets are only rated at 13A for both outlets? So if your mrs is drying her hair while your putting the kettle on, in the same socket, it exceeds its rating? Talk about design flaw.

 

[Andy™]

Double sockets are only rated at 13A for both outlets? So if your mrs is drying her hair while your putting the kettle on, in the same socket, it exceeds its rating? Talk about design flaw.

BS1363 only requires 13A between both outlets. always has. check just about any socket and it will says '13A'. cheap sockets probably overload at that, but more decent ones last longer (iirc, MK did a thing a while back where they pulled 13A from each side. lasted a day or 2 before any damage, and ran for much longer at 10A per side)

 

[spinlondon]

I thought that the testing requirements for double sockets to BS1363 were that the sockets are tested with 14A on one socket, and 6A on the other, a total of 20A to match 2.5mm

 

[Andy™]

any links?

 

[spinlondon]

Sorry, no BSI don't seem to publish their stuff on the net.

Here's a copy of what I've got:

"BS1363-2:1995 requires for double socket outlets that both socket outlets have loads applied via test plugs, 1 test plug having a load of 14 amps whilst the other has a load of 6 amps, making a total load of 20 amps on the cable supplying the double socket outlet. The double socket outlet is then subjected to this loading for a minimum continuous period of 4 hours or longer until stability is reached with a maximum duration of 8 hours (stability being taken as less than 1 degC rise within 1 h). The test is passed if neither the terminals / terminations, nor the accessible external surface, increase in temperature by more than 52 degC."

 

[Mark2spark]

I didn't think you could spur off a 2.5 ring in anything less than 2.5 unless fused?

That's also how I was taught.

I understand the 'downstream' demand tho', although I think uniform 2.5's until the actual fuse is better practice and unlikely to raise eyebrows should inspections arise for some reason or another.