Rcbo

[electrotron]

Hello,

I'm currently training and have been for 3 years.

Today we are 2nd fixing a house.

There are 2 lighting circuits, both connected to the RCBO.

When the earth is connected it trips. Now i know there may be a fault between n and e. When tured on with the e out the RCBO sets. If tested between earth of the circuit and the met and it showed 50v. But no matter what earth of the lighting circuits connects to the cu it trips one?

Could the circuits be mixed up eg. One L from a circuit is in with the N of the the other?

 

[Andy™]

erm... in your 3 years of training, has no-one covered how to I&T wiring? you definately have a fault, and it should have been picked up before the power was switched on...

 

[electrotron]

Yes. Not carried out a test yet. As we tried to get the lights on for the last hour. We will test I will carry out some testing in the morning but was hoping you lot could help shed some light on it.

I will split the circuit in half and work from there.

I think it's strange how both earth's trip the same RCBO?

 

[Andy™]

so you just skipped all I&T and gone with the breaker test.

until you actually bother to do what your suposed to do, no-one can tell you what the fault is. once you actually do the testing you will soon know what the fault is, then you can start finding it.

really, im surprised you didnt just remove the RCBO and stick the cable into the main switch

 

[ProDave]

That's a very strange fault finding technique, to remove the earths until you clear the fault.  

you shouldn't be voltage testing to your earths, but insulation testing with the circuits DEAD.

Almost certainly a N-E short somewhere.

As already stated you shouldn't just power up without testing properly first. You mentor is setting a bad example.

 

[electrotron]

I knew it was a n and e fault straight away. That's I tested to the earth to see how much voltage come through. Didn't have a tester on site but will test it tomorrow

I understand about testing before powering up but in the case we only wanted it on for a hour so we could pack up.

 

[ProDave]

That's what plug in work lights are for.

 

[electrotron]

Anyway so know will try to help just say should of tested before witch I already know. But why does it trip when both earth are connected ?

 

[Andy™]

its tripping because of a fault. unless you actually do some testing, you wont know what the fault is... were not magicians here.

 

[Murdoch]

Just take out the RCBO and fit a MCB and forget any testing - then collect your horse from the stable block

 

[electrotron]

Really helpful you lot

 

[Murdoch]

Really helpful you lot

Matey - how can you expect us to help you unless you can tell us your test results - without them we would be speculating.

What we can say with some certainty - is that you have a fault to find!

 

[Blue Duck]

Board change? Should test first so you can rectify any faults! saves hassle in the long run and also saves getting abuse on here for not doing ìt.

 

[Andy™]

2nd fixing a house kinda implies a re-wire?

 

[electrotron]

Yes I know. I'm taking it, there is a short between n and e.

The bit I am struggling with is to why if I connect both cpc in the earth bar then why does one RCBO rip? And not the other.

We didn't do the consumer unit install.

Could it be possible the N are connected to the wrong RCBO ..?

It's been rewired

 

[Murdoch]

Yes I know. I'm taking it, there is a short between n and e.

The bit I am struggling with is to why if I connect both cpc in the earth bar then why does one RCBO rip? And not the other.

We didn't do the consumer unit install.

Could it be possible the N are connected to the wrong RCBO ..?

It's been rewired

Why would both RCBO's trip?

 

[electrotron]

No... only one rcbo trips if both earth are connected

 

[Murdoch]

No... only one rcbo trips if both earth are connected

Interesting - are you saying that if either are connected its OK??

Still think you need to step back and do some proper testing

 

[Blue Duck]

2nd fixing a house kinda implies a re-wire?

Oops my bad!

 

[electrotron]

No. The earth has 50v through it.

When all connected one rcbo will not set. Witch is a n to e fault. Correct?

When disconnecting the earth it sets but the earth has a voltage of 50v.

When the other cpc is connected the same RCBO trips even though it's not the same circuit.

As I said could the l and n be swapped in the wrong rcbos?