RCBO Blew Up

[LewisM]

Hello I you are all well

This is hard to explain but basically doing a three phase install and there is no power yet so I wanted to test two lighting circuits before the lifter went, I used an extension lead and connected live to phase L2 (that's what the lights were on) Neutral to the neutral bar and Earth to the earth bar (see attached picture) however the extension lead I was given had been wired with reverse polarity L-N switched so when powering on with all circuit breakers OFF one of the RCBOs blew up as it had a backfed neutral, power was quickly removed however has the integrity of all the RCBOs been compromised?

Thanks Lewis

 

[Lucien Nunes]

This would not have happened if the full sequence of initial inspection and testing had been followed

But at this point the question is what caused the RCBO failure, as even though there was a procedural deviation leading to a reverse polarity connection, I agree that this alone shouldn't make it go bang. It might have been defective and gone bang anyway with a normal supply, or there might be a subtle shortcoming in the design that is not generally known.

Can you break open the RCBO so we can study the failure mode?

 

[suffolkspark]

Would also be interested if you can drill it open and get some pics

 

[LewisM]

Will do on Monday

 

[LewisM]

Got nice and hot then

 

[Lucien Nunes]

Hmm. Are you sure that was running from a 13A extension lead?
The initial failure led to a more extensive power arc that will have covered much of the evidence in soot. For forensic purposes I am sure it would yield information given enough time and care to extract.

It would be interesting to know what Hager technical say. If it were mine I would contact them, state that an RCBO failed on a reverse-polarity supply and see if they can can add anything. They might even be interested to have the failed device back for inspection.

 

[AJshep]

Seems very odd. Out of interest where was the extension lead plugged in... was it plugged into a single phase circuit on a 3 phase system?
Did you verify the voltage of the extension lead between all conductors?

Poor neutral connections can present themselves as reverse polarity and cause higher then normal voltage to run through the coils. Maybe the problem is with the existing circuits.

 

[LewisM]

Yeah was a 13A plug that was wired to a Dura plug, the Dura plug live had been wired incorrectly as I tested it after and there was reverse polarity, I took it apart after and the lead was wired wrong

 

[LewisM]

Yeah was a 13A extension lead that had been wired to a Dura plug, the Dura plug live had been wired incorrectly as I tested it after and took it apart

The Dura plug lead was plugged in to a an extension lead had been used to charge batteries etc for two weeks

 

[pc1966]

Did the fuse in the extension lead blow?

I'm struggling to see how it was a high-current fault and beginning to think it is the FE that can't stand long-term reverse power. Which is odd as the last measurement I did (by accident) suggested no real issue in terms of dissipation on a open neutral sort of fault.

 

[LewisM]

Did the fuse in the extension lead blow?

I'm struggling to see how it was a high-current fault and beginning to think it is the FE that can't stand long-term reverse power. Which is odd as the last measurement I did (by accident) suggested no real issue in terms of dissipation on a open neutral sort of fault.

No fuse didn't blow, breaker replaced and all working and tested fine now