neutral earth fault

[dave1064]

During my zs tests on the ring circuit the rcbo trips. The breaker also trips when I take a Zs on the cooker. I have carried an insulation resistance test on the cables and have found a dead short (0.00) Mohm reading on the neutral and earth on the ring circuit. 137 between line and earth and 87 between neutral and line both these readings not great but acceptable.

Why is the rcbo not tripping straight away when energised?

I have changed the rcbo too.

 

[AndyL]

During my zs tests on the ring circuit the rcbo trips. The breaker also trips when I take a Zs on the cooker. I have carried an insulation resistance test on the cables and have found a dead short (0.00) Mohm reading on the neutral and earth on the ring circuit. 137 between line and earth and 87 between neutral and line both these readings not great but acceptable.

Why is the rcbo not tripping straight away when energised?

I have changed the rcbo too.

These readings do not make sense, if you have short circuit N-E you would be getting the same reading between L and E as you get between L and N

 

[Fox]

It sounds like you may still have equipment left connected to the circuits under test.

What tester are you using? Some testers will trip an MCB/RCBO under test, and if this is the case you might have to calculate your Zs manually if you have a measured R1+R2 value

 

[MDJ]

During my zs tests on the ring circuit the rcbo trips. The breaker also trips when I take a Zs on the cooker. I have carried an insulation resistance test on the cables and have found a dead short (0.00) Mohm reading on the neutral and earth on the ring circuit. 137 between line and earth and 87 between neutral and line both these readings not great but acceptable.

Why is the rcbo not tripping straight away when energised?

I have changed the rcbo too.

There's a fault I suspect, however before getting into that did you do the ZS test with the non trip function lol

 

[snowhead]

Neutral disconnected at C.U during tests?

 

[trev]

These readings do not make sense, if you have short circuit N-E you would be getting the same reading between L and E as you get between L and N

Not necessarily. Can you explain your logic mate.

 

[guest119]

The rcbos will trip because you are sending current to earth, the very thing they are there to stop.
Dead short n-e, yes of course, they are the same thing.
Rcbo does not trip when energised because it is seeing no fault (or you have killed it with your megger).
Maybe time to say who you are so we can understand why you are having problems with such basic stuff.IE are you a young tradesman, apprentice, Electrical Trainee, mate?

Boydy

 

[trev]

Rcbo does not trip when energised because it is seeing no fault

Because until there is something flowing in the N the fault isn't picked up

 

[snowhead]

Maybe time to say who you are so we can understand why you are having problems with such basic stuff.IE are you a young tradesman, apprentice, Electrical Trainee, mate?

Boydy

from an earlier thread;

Im a 4th year apprentice due to sit my trade test in 2 weeks. So been studying etc. And the question was asked why it is 0.8. Just wondered how they came up with 0.8 ohms

 

[guest119]

4th year apprentice, a rare breed these days, respect.
Can you please answer the question in post 5, it is very relevant.

Boydy

 

[Octopus]

During my zs tests on the ring circuit the rcbo trips. The breaker also trips when I take a Zs on the cooker. I have carried an insulation resistance test on the cables and have found a dead short (0.00) Mohm reading on the neutral and earth on the ring circuit. 137 between line and earth and 87 between neutral and line both these readings not great but acceptable.

Why is the rcbo not tripping straight away when energised?


I have changed the rcbo too.

Nothing wrong with these figures.

Is there a neon somewhere?

 

[Knobhead]

Could I ask the earthing arrangement?

There’s a basic thing you could all be missing.

 

[dave1064]

Sorry been busy. Yeah 4th year apprentice trade test next week. I realise its a stupid question I had a bit of a brainfart. Too much going on at this job. Its a tncs system.

I suppose we all have these daft moments

 

[DJ Ovengloves]

Ah ha! I think Tony's point has been made