UK RCBO intermittent tripping advise??

[ipf]

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He affords them by not paying out for unnecessary work to be done on his house.
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Nooo, but it helps a bit to pay the fuel bill.....

 

[leebut]

He affords them by not paying out for unnecessary work to be done on his house.
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Nooo, but it helps a bit to pay the fuel bill.....
[/QUOTE]
He's an accountant so probably doesn't pay the taxman very much money each year

 

[Markyd]

So the house had a few probs before you changed the board.....Alarm bells should have rung then.EICR was prob ok but you should have put in writing that any remedial work that needed to be done after board change would be down to them to cover cost of investigation and remedial work

 

[Wilko]

Hi - if I’ve understood correctly it’s just this one circuit with the one transformer that sometimes trips? - other than changing the RCBO as already suggested you could perhaps also :

- confirm from the board the circuit has “excellent“ continuity (with the transformer primary bypassed) and insulation resistance.

- see if the fault moves with the transformer.

-replace the switch, as it’s not impossible that contact bounce is annoying the RCBO somehow ...

 

[radiohead]

There's your answer then, a D type is most unusual and probably non compliant in a lot of domestic situations, I expect the new RCBO serving the kitchen lights will have a 'B' tripping curve, if the customer doesn't agree to new LED lights a C type 10a RCBO might do the trick.
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The D type MCBs were originally fitted to counteract the high inrush current and nuisance tripping with the old toroidal transformers I expect.

Why would a type D 'probably be non compliant in a lot of domestic situations'?
If the measured Zs is satisfactory.....and anyway the OP stated there was originally an RCD main switch which largely negates any OCPD Zs issues.

 

[Dave OCD]

Why would a type D 'probably be non compliant in a lot of domestic situations'?
If the measured Zs is satisfactory.....and anyway the OP stated there was originally an RCD main switch which largely negates any OCPD Zs issues.

I knew there would be at least one picking up on that, I was referring to existing installations where there may not be RCD protection on the lighting,and the measured Zs could be unsatisfactory.How often have you seen type D MCBs in domestic installations ?

 

[HappyHippyDad]

I think it’s fine to offer the option of replacing the ELV lights but I’d be making it clear that it is just a good idea and not a necessity. I would be changing the B type RCBO for a C type free of charge if they chose not to change to GU10’s.

 

[radiohead]

How often have you seen type D MCBs in domestic installations ?

Hardly ever, doesn't mean they are likely to be non compliant though.

 

[Vortigern]

Bit of a stab in the dark here. I have encountered tripping on RCD where there is two way switching due to the way the 3 core was connected. By changing the cores around at the switches the RCD tripping stopped due to the "centre" (for want of a better description) cable being adjacent to the cpc no longer. You did seem to mention testing the switches both ways. Sorry if I have misunderstood, but I took that as there is two way switching in the kitchen?

 

[HappyHippyDad]

Hardly ever, doesn't mean they are likely to be non compliant though.

I would say a 6A D type MCB or RCBO would have a 50% (approx) chance of being non compliant in a domestic situation as the Zs would have to be max 1.46Ω (TT).
I would say a 32A D type MCB or RCBO would have a 98% (approx) chance of being non compliant in a domestic situation as max Zs is 0.28Ω (TT).

My aspergery brain starts overheating when the word 'likely' is used as it is so subjective! It doesn't mean anything in this scenario. Even my approximations above are ridiculous as they are only ever so slightly less subjective.
It's a bit like that old 80's film 'war games' when the computer tries to find a winner in nuclear war and breaks down due to infinite 'no win' outcomes.

I will now stop drinking coffee.