RCBO trip when cabinet lights switch on

[Timotei]

Call out for tripped 20A RCBO on TT system, 3 Halolite T4 fluorescent cabinet lights (class 2) on 3A FCU from radial socket circuit, trips occasionally when lights are switched on.

Circuit tested including IR, all results good, RCBO tested including ramp test, all good.

Connections checked, all good.

No unexpected earth leakage shown with clamp meter on tails.

Can recreate the trip when all 3 lights are on, but turning any one off at its own switch so that only 2 are switched on / off via lightswitch the fault cannot be recreated.

Thoughts please.

 

[suffolkspark]

if there's no loose connections change the FCU

 

[littlespark]

cumulative fault over the 3?
It only happens with the lights?
If it does, then change the lights.

 

[EbolaSideRoom]

Yes to the above; also check the links between the lights - are they under one cabinet or is there a link between cabinets?

 

[littlespark]

Is one of them located above the spout of a boiling kettle by any chance?

 

[Timotei]

Thanks for your thoughts so far....

lights are actually being used to illuminate understairs cupboard, so all cables / links visible and appear undamaged, no steam or moisture present.

Littlespark, I also assume / consider likely a cumulative effect of the 3 lights, but as should be able to link up to 6 on a smaller RCBO / MCB by manufacturers instructions I also assume that at least 1 may be faulty.

I am going to disconnect lights from the circuit and PAT test when go back and see if anything shows up, didn't have time for this yesterday.

Suffolkspark, will try FCU change as a cost effective "worth a go" before changing lights if nothing else "comes to light" - sorry about the pun!

Timotei

 

[Wilko]

Hi - sounds like faulty light. Happy hunting !

 

[DPG]

Let us know!

 

[Timotei]

Just been back...

With benefit of more light (and glasses!) what I thought were ECP's on the lights were in fact plastic, so didn't pursue further testing there.

Lightswitch and FCU both good.

Gut feeling the lights are sound, and don't want to go replacing them only to have the same issue......so temporarily connected the circuit into another RCBO....unable to reproduce the fault.

So now thinking dodgy RCBO, depsite testing correctly on 0.5 / 1 and 5 x, plus ramp test 25mA.

It's a BG compact RCBO and I have read somewhere else on the forum that there have been issues with some of these, although I can't now find the relevant thread or remember specifically what the issue was.

Are there any further tests to try on the RCBO before trying a replacement?

Anyone able to tell me anymore about the BG compact RCBO "issues"?

Timotei

 

[Pete999]

What are the results of the tests? all good is an over compassing reply

 

[Timotei]

IR > 999
Ra 146Ω
PFC 1.3kA
Zs 16.5
RCBO x0.5 no trip x1 23ms x5 19ms ramp 24ms
Earth leakage max on circuit measured at L/N tails 0.2mA

 

[DPG]

Zs 16.5?

 

[Timotei]

Zs 16.5?

Zs 16.5Ω TT system, max Zs on 30mA = 1667Ω (4.11.5.3)

had a couple of vinos now, so I may be reading the chinese takeaway menu rather than the regs!

 

[suffolkspark]

Well at least swapping out the rcbo sorted it, good ol BG