Single or DP RCBO (Debate continued, split from "old fuseboard" thread)

[mainline]

at least with an RCBO board, and fault will only take out the affected circuit and not half the circuits

That would only be true when using DP Rcbos

I have split these posts (From "Need help, old fuseboard changed...........") so the debate can continue. They will only serve to confuse the OP

 

[Murdoch]

That would only be true when using DP Rcbos

Not sure I agree with that

 

[mainline]

Not sure I agree with that

An Sp rcbo will not clear an N to E fault.

 

[Murdoch]

An Sp rcbo will not clear an N to E fault.

But only the affected one will trip.

 

[mainline]

But only the affected one will trip.

A N to E fault can trip random rcbos.

 

[UNG]

A N to E fault can trip random rcbos.

I have had that problem before looking for a fault on the wrong circuit

 

[Murdoch]

A N to E fault can trip random rcbos.

Can but more often than not the tripped RCBO is the circuit with the fault

 

[Tim Howard]

It's quite easy to talk at cross purposes here. The point about RCBO boards is the N's are joined upstream of the RCBO test coils that look for the imbalance.
Whether SP or SP with switched N this doesn't change.

That said, SPSN (DP) RCBOs are much more convenient for testing and fault finding and all new boards I fit use them.

 

[mainline]

It's quite easy to talk at cross purposes here. The point about RCBO boards is the N's are joined upstream of the RCBO test coils that look for the imbalance.
Whether SP or SP with switched N this doesn't change.

That’s true but a DP rcbo will isolate the circuit that causing the trip where as an SP one won’t.

 

[Tim Howard]

That’s true but a DP rcbo will isolate the circuit that causing the trip where as an SP one won’t.

That's what I thought you might have meant, hence my comment about cross purposes!

 

[Tim Howard]

I used to think that DP RCBOs were more essential than they in fact are.
Detection is the same.
A L-E fault is isolated.
An N-E fault that isn't isolate by a SP RCBO will on many installations just be duplicating a TN link in the head. (There are exceptions of course!)
I'm more recently thinking that the main people who like them and benefit from them are us electricians!

 

[mainline]

DP rcbo is most beneficial in a TT earthing system where an upstream rcd is being used.