Very strange fault with video

[RF Lighting]

Just going through my phone and found this video from a few years ago.

This was a brand new TP&N dist board installed at a church by the firm I was working for at the time.

Supply was standard TNS on a 100A incommer.

The two circuits concerned tested out fine for IR L>N L>E E>N and also all combinations of LNE between the two circuits to prove there were no interconnections.

Can anyone work out how this could possibly happen??

 

[SUNRAY]

Well now you mention it...





No, but I'd love to know the answer.
Did it do the same thing on a real RCD trip?

 

[EFLImpudence]

Assuming it is only that one MCB that affects the RCBO, I'm thinking - how did you even find out it did that?

 

[RF Lighting]

From what I remember we were testing the installation for the EIC following the board change which was part of the works of refurbishing and rewiring the meeting and coffee rooms after asbestos removal.

It was when we did an RCD test with a tester at a socket that we couldn’t get the RCBO to reset and we first saw any problem.

I can’t remember exactly how we found out that switching the breaker off allowed the RCBO to reset, but this was the only breaker which affected it.

We spent a good while going through everything and really testing out everything we could think of and never found anything at all which was out of the ordinary.

In the end it was left like this. I wonder if it is still like this today!

 

[SUNRAY]

I had something similar to this in the workshop I spent a year Buiding panels, there was a sequence we needed to follow when swicthing on in the morning otherwise the 'after board' RCD would trip.
It took a bit of head scratching but turned out the 'N' & 'E' busbars were swapped and effectively linked by the containment and sockets.

 

[333rocky333]

Isnt it just the time after the test button is operated, residual current somehow, whilst your going over to the other Mcb, nothing in the video suggests it would not have reset after a few seconds regardless of you doing the other Mcb.
Failing that maybe somehow induced by the type of load on the other Mcb

 

[SUNRAY]

Isnt it just the time after the test button is operated, residual current somehow, whilst your going over to the other Mcb, nothing in the video suggests it would not have reset after a few seconds regardless of you doing the other Mcb.
Failing that maybe somehow induced by the type of load on the other Mcb

I've built a healthy respect for RF work and abilities, only through these hallowed pages, and I'd imagine that he would have found if that was the case during the stated testing.

Is this single in containment? I wonder if a pair of wires [originally intended as a circuit managed to get split across 2 circuits] is able to provide enough leakage. But that still wouldn't explain the symptoms.

 

[securespark]

I have had several cases (albeit on SP supplies) of stuff connected to the circuits (appliances etc) that can prevent RCD's resetting. I even had a couple of RCD incomers fail the auto and ramp tests, but when the RCD was tested in glorious isolation, it was A1.

They involved older MK and Memera boards, the one with the badminton racquet switch.

 

[RF Lighting]

I can’t remember exactly but I think the RCBO circuit was a pyro fed sockets radial and the MCB circuit was one of our new lighting circuits which was LSF singles in steel trunking / tube.

It wasn’t just a time delay thing. The RCBO would not reset at all until the lighting circuit was switched off.

If memory serves me right the lights were PL downlights and some 8W emergency bulkheads. Nothing out of the ordinary at all.