Borrowed Neturals!!

[ajelec10]

Just another pain in the back side, us sparks need to consider when undertaking new Cu changes.
Did a little domestic the other day changed the board using rcbos, turned on dowstairs lights fine turned on upstairs and bang both rcbos trip. Ovi a borrowed nutural! ********, after a little digging i found a t+e from the landing light switch with the netural and cpc cut out going to the downstairs hall light at the hall light another t+e with the line cut out going to a dowstairs JB to pick up a netural!!

Works fine on the old board. just waiting to cause you problems!!

AJ

 

[patricklondon]

this keeps cropping up, usual solution as a minimum if not rewire is to put them both on the same circuit

 

[rob1967]

this keeps cropping up, usual solution as a minimum if not rewire is to put them both on the same circuit

How would you go about this? would you put both tail ends into the same rcbo?

 

[d1scv]

No- I think he assumed a split load board, and putting both circuits behind the same RCD.
With RCBOs you hve a problem.
I've learnt to run the tests for this before pricing after catching a couple of bad colds.

 

[rob1967]

is Putting two circuits into the same breaker against regs? cant find anthing in the regs so far...........

 

[m4tty]

aint lighting circuits supposed to go on seperate rcd to minimise danger in event of fault. A fault will knock the whole house lighting out ??

 

[rob1967]

Not to minimise danger but inconvenience, Ideally it would be good to split them.......

 

[Yooj]

aint lighting circuits supposed to go on seperate rcd to minimise danger in event of fault. A fault will knock the whole house lighting out ??

See Section 314 in the regs, specifically 314.4

Yooj

 

[patricklondon]

seperate circuits should be on seperate breakers yes. but if there are two breakers say for upstairs and downstairs lighting circuits when the user or electrician thinks they have isolated the circuit the neutral that has been 'borrowed' can still become energised with great risk of injury or death particularly when you think it is safe to handle exposed conductors. ideal solution is to rewire where neccessary. where this is not possible or costs will not permit then joining both live feeds together into one (possibly different rating) breaker is acceptable as asafer alternative.