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RCBO tripping mystery

Former Community Member over 4 years ago

Hello,

Can RCBOs trip if their integral neutral lead is too long?

Went to look at a tripping problem for a customer today, he had a lighting circuit and an alarm system connected to RCBOs that have started tripping.

As you will all know, an RCBO has terminals for the circuit live and neutral, as well as its own neutral that goes to the neutral bar. When I arrived, I found the RCBO neutrals for these two circuits disconnected and taped. I did a quick check by disconnecting the circuit neutrals and putting them directly into the neutral bar in the board, both circuits worked fine, as soon as I put the circuit neutrals back into the RCBOs and put the dedicated RCBO neutrals into the bar, which is how they should be configured, the circuits started tripping.

I noticed that the other circuits, sockets, immersion heater, etc. were also on RCBOs, but the dedicated neutrals for them had all been shortened. It was only the two with long neutral leads that were tripping. I asked the customer’s permission to shorten them to the same length as the ones on the other RCBOs, but he refused; I couldn’t argue with him as it was his property.

Thanks for any advice.

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0 Former Community Member over 4 years ago

(@Sparkingchip ? I wish I could say I haven't seen the same -- I did see the result of someone thinking they had to ferrule something but without a crimper had obviously used the "cutting" part of ordinary pliers to crush a single pair of lines into the ferrule! High-resistance joint?)

@Chris Perhaps the instruction is only on "industrial" device instructions, but the guide has a wordless pretty picture showing that the exposed conductor should go into an uninsulated tube and then into a terminal. "A picture speaks a thousand words" and yet sometimes just a few words can make an incomprehensible picture entirely make sense! I suppose it removes the need for language-specific sheets, and yet this guide was otherwise written in English :-/

Most mfr's crimp the ends but what you get from EatonMEM is a "compression" weld (probably the wrong term, I'm no mechanical engineer) to virtually melt the strands together. Exactly the same effect for the same purpose and treated in the same way: use it or crop-it-and-crimp-it according to circumstance.
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0 Former Community Member over 4 years ago

(@Sparkingchip ? I wish I could say I haven't seen the same -- I did see the result of someone thinking they had to ferrule something but without a crimper had obviously used the "cutting" part of ordinary pliers to crush a single pair of lines into the ferrule! High-resistance joint?)

@Chris Perhaps the instruction is only on "industrial" device instructions, but the guide has a wordless pretty picture showing that the exposed conductor should go into an uninsulated tube and then into a terminal. "A picture speaks a thousand words" and yet sometimes just a few words can make an incomprehensible picture entirely make sense! I suppose it removes the need for language-specific sheets, and yet this guide was otherwise written in English :-/

Most mfr's crimp the ends but what you get from EatonMEM is a "compression" weld (probably the wrong term, I'm no mechanical engineer) to virtually melt the strands together. Exactly the same effect for the same purpose and treated in the same way: use it or crop-it-and-crimp-it according to circumstance.
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RCBO tripping mystery

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