Extra leg on 4mm Radial

[Subneural]

Hi Guys,

I've got an existing 4mm Radial on a 32A RCBO which I've been asked to add another point to about halfway down the run.

As its 4mm I've no chance of getting another 4mm cable in the back of the existing socket but should be able to squeeze a 2.5mm in for a 12 inch length to a FCU.

Would this be ok ?

 

[Badger]

Hi Guys,I've got an existing 4mm Radial on a 32A RCBO which I've been asked to add another point to about halfway down the run.

As its 4mm I've no chance of getting another 4mm cable in the back of the existing socket but should be able to squeeze a 2.5mm in for a 12 inch length to a FCU.

Would this be ok ?

no because 2.5 cant take 32amps, it can onlu take 27amps youd need to lower the breaker to 20amp if your looking at using 2,5 mm t+e

 

[Apache]

Badger - if he's running to a FCU in 2.5mm is it not ok if fused to 13A?

 

[Badger]

Badger - if he's running to a FCU in 2.5mm is it not ok if fused to 13A?

no because its still got to be protected at the correct ampage from the breaker, as if a fault occurs in the 2.5 the cable could possibly melt and cause fire, under load / fault conditions the 2.5 can only take a maximum of 27 amps, where as the breaker is 32 amp BEFORE it will trip...

 

[Marc]

no because its still got to be protected at the correct ampage from the breaker, as if a fault occurs in the 2.5 the cable could possibly melt and cause fire, under load / fault conditions the 2.5 can only take a maximum of 27 amps, where as the breaker is 32 amp BEFORE it will trip...

Nothing against regs though, Appendix 15 433.1 p363 BRB...

 

[Andy™]

no because 2.5 cant take 32amps, it can onlu take 27amps youd need to lower the breaker to 20amp if your looking at using 2,5 mm t+e

i fail to see how what he plans is any different from a 2.5 spur from a ring feeding a FCU

the FCU will protect the 2.5 against overload. the 32A MCB will protect againt fault current

 

[Subneural]

Thanks for the responses guys.

My thought train was that 12 inches of 2.5 might be able to take 32A before it links to the FCU. But as I'm on site I can't check myself till tonight

 

[tom1]

i got two 6mm cable into back of socket,

pg 363 brb shows2.5 being taken off the 4mm by junction box, i cant see how taking it from a sockts is any different as long as u dont add another socket after that

 

[Riggy]

Hi Guys,I've got an existing 4mm Radial on a 32A RCBO which I've been asked to add another point to about halfway down the run.

As its 4mm I've no chance of getting another 4mm cable in the back of the existing socket but should be able to squeeze a 2.5mm in for a 12 inch length to a FCU.

Would this be ok ?

Absolutely fine, go for it.

 

[paul b b]

Its ok to spur off with 2.5 it makes no odds at all if you have a 32A mcb, you will have a 13a fuse in the FCU so it will protect the cable.

i can see no difference in spuring off a 32A radial to 32A ring

 

[batty]

My thoughts are a 12'' piece of 2.5 will be short enough to have enough fault current should there be a short circuit on it and as the max it will take is 13 amps although possibly a bit more it is never going to be overloaded so I would do the job.

Batty

 

[NozSpark]

I don't think you would even need a FCU (unless you were adding a chain of 2.5mm fed sockets).. the fuse in the plugtop will protect the cable.

 

[Andy™]

I don't think you would even need a FCU (unless you were adding a chain of 2.5mm fed sockets).. the fuse in the plugtop will protect the cable.

you dont need a FCU.... as Tom1 says above, page 363 of BRB shows a 2.5mm branch from 4mm

 

[NozSpark]

Ooooppppss,

must have speed read straight past that one!!