borrowed neutral

[spydaweb]

hi just a query
i've heared about somthing called a borrowed neutral
am i right in thinking that this is a neutral taken from another circuit?
if so isn't this a dangerous practice as if im thinking right the ciruit with the borrowed neutral will not isolate when is circuit breaker is opened. also if this practice does go on what are the benifit to the installer?

 

[breezer]

you are right.
There is no benefit to the insatller, its just some people really do do it unintentionaly, others do because they know no better, look in for refence there is a drawing

and yes it is dangerous

 

[t4msy]

I love the way they call it "borrowed" neutral. Shold be stolen neutral since they never had any intention of returning it.

 

[ban-all-sheds]

and yes it is dangerous

Only if you don't know about it. If properly documented you can remove the danger by isolating both circuits.

 

[plugwash]

there are two situations in which borrowed neutrals are usually seen

one is wall lights. People add a gang to a lightswitch and link the live accross but need a neutral from somewhere they get this in one of several ways (none of theese methods would be considered acceptable by reputable electrictions)
1:borrow it from a socket
2:use the earth as a neutral
3:misuse the earth core in the cable used as the switch drop so they have enough cores for a live switched live and neutral.

the other is a method of two way switching that was common before 3+E cable became common



this *should* only be done when the lights are on the same cuircuit but is often seen done accross cuircuits