Neutral lead on RCBO'S

[Kev2632]

What exactly are the neutral leads for? and if a neutral to earth happened on a board with just RCBO'S in it, why doesnt the fault travel along that neutral and affect the other RCBO's?

 

[GLENNSPARK]

because the neutral from the circuit being fed from the RCBO has to go through the RCBO before it gets to the neutral bar vie the RCBOs neutral lead.....so any imballances due to fault between neutral-earth are seperated from the other RCBOs/RCDs within the install....unless in series of course

 

[Kev2632]

because the neutral from the circuit being fed from the RCBO has to go through the RCBO before it gets to the neutral bar vie the RCBOs neutral lead.....so any imballances due to fault between neutral-earth are seperated from the other RCBOs/RCDs within the install....unless in series of course

So the fault is detected within the RCBO before it will travel back along the Neutral lead is at right yea?

 

[Guest55]

Q1 to complete the circuit

Q2 because only one rcbo will detect the imbalance and trip.

 

[Top Cat]

And why do they have curly neutrals so you can't do a neat job!

 

[Kev2632]

Q1 to complete the circuit

Q2 because only one rcbo will detect the imbalance and trip.

So the fault is detected within the RCBO before it will travel back along the Neutral lead is at right yea?​

 

[GLENNSPARK]

And why do they have curly neutrals so you can't do a neat job!

because their pigs TC...

 

[GLENNSPARK]

RCBOs have flying neutrals that terminate into a common neutral bar...yes?....so as the final circuit is connected THROUGH each individual RCBO....both line AND neutral.....so the RCBO will detect imballance without upsetting the ballance of any other RCBOs within that C/U....

 

[Darkwood]

And why do they have curly neutrals so you can't do a neat job!

Whether post in humour or not the reason is its fine wire and to terminate it it has to be crimped, the factory crimp it for you but if it was just one long lead ppl would shorten it more readily and probably ignore the regs and not crimp, this has a risk of poor termination which can cause overheating, nuisance tripping etc etc, the manufacturers would get more returns thinking rcbo faulty because of poor terminated neutrals due to sparkies cutting long leads to length.
I do recall they used to be long leads on some brands once upon a time.

 

[Guest55]

RCBOs have flying neutrals that terminate into a common neutral bar...yes?....so as the final circuit is connected THROUGH each individual RCBO....both line AND neutral.....so the RCBO will detect imballance without upsetting the ballance of any other RCBOs within that C/U....

i said that , but just with less words :-D

 

[Kev2632]

If somebody was to take a neutral from 1 rcbo circuit and it joined up with another rcbo circuit further down the line, and there was a neutral to earth fault on the first rcbo won't the fault travel along that neutral link and cause the other rcbo to trip as well? Or not??

 

[Darkwood]

your looking at this wrong rcbo's will only detect faults on the load side any neutral/earth faults on the supply side of the rcbo wont be seen, it looks at the current going to the load matches the current coming back, if their is a difference then it is leaking elswhere and if large enough will trip the rcbo. This will not effect another rcbo on the same neutral bar as that is monitoring only its own load.

 

[Kev2632]

Yea i understand what you mean, what I'm meaning is if there was a borrowed neutral on the load side of the rcbo " a link between two rcbo e.g on two lighting circuits" and there was a earth to neutral fault on one rcbo why won't that affect the rcbo number two ??

 

[Darkwood]

Yea i understand what you mean, what I'm meaning is if there was a borrowed neutral on the load side of the rcbo " a link between two rcbo e.g on two lighting circuits" and there was a earth to neutral fault on one rcbo why won't that affect the rcbo number two ??

A - if there was a borrowed neutral then this would trip the rcbo anyway as there is an imbalance of load out and return as the current would be higher on the return path when borrowed neutral load was switched on, but hypothetically if you could maintain the circuit and and then touch down neutral to earth it will only trip the rcbo that is leaking the current and has seen an imbalance, this will depend on many things like where the short is, cable resistance , volts drop etc etc all playing a part in where the neutral current will leak to and how much, its possibly alot more complicated than it should seem.

 

[Knobhead]

13 posts to find out it has absolutely nothing to do with the flying leads.

The RDBO’s will act as any two RCD’s would with a shared neutral. They will trip on current imbalance, it doesn’t even need an earth fault to cause the tripping.

 

[Kev2632]

So it is possible for two rcbos to trip if somebody borrowed a neutral from two different circuits and there was neutral to earth fault on one circuit yea?

 

[Darkwood]

A - if there was a borrowed neutral then this would trip the rcbo anyway as there is an imbalance of load out and return as the current would be higher on the return path when borrowed neutral load was switched on, but hypothetically if you could maintain the circuit and and then touch down neutral to earth it will only trip the rcbo that is leaking the current and has seen an imbalance, this will depend on many things like where the short is, cable resistance , volts drop etc etc all playing a part in where the neutral current will leak to and how much, its possibly alot more complicated than it should seem.

Also in answer to your question is that when the rcbo trips it will stop the current flowing in the borrowed neutral so the second rcbo dosen't see it, which rcbo trips will be down to the variables mentioned above.

 

[Knobhead]

I give up!

 

[Darkwood]

So it is possible for two rcbos to trip if somebody borrowed a neutral from two different circuits and there was neutral to earth fault on one circuit yea?

I would say it is possible but more than likely just one may trip, im just theorising here but your best bet is to build a little circuit and do as you said with the neutral then link one to earth, repeat several times and then see what happens, but i only suggest this if you are competent to do this, as you will be experimenting live. Probably the quicker way of finding out as your going around in circles here we've explained the best we can.

 

[Kev2632]

see attached rubbish drawing, but it gives you the idea im trying to explain what would happen if somebody borrowed a neutral one circuit and took into the other circuit which are bother RCBO protected, and there was a neutral to earth fault on the 1 circuit would it affect the other RCBO, and ive been told your not "borrowing the neutral because there is split board its a common neutral but why doesnt the RCBO detect two different neutrals from different circuits if they are joined together at some point ??