RCBO Trips After 10 seconds

[Robert0911]

Hello - I wonder if anyone can give me some advice about the following:

My house has two outside lighting circuits (front lights and back lights). These are controlled via separate switches which are connected to a 6amp RCBO (30mA B curve) in the CU. Each circuit has 20x GU10 LED spots at 5w each. So each circuit is around 100w. (total 40 spots/200w). If I switch both front and back lights on the RCBO trips after 10 seconds - every time. If I just switch on one circuit (either front or back) the RCBO does not trip. This is relatively new behaviour - in the past I have had both front and back lights on with no issues. The only change is that I have replaced some blown spots (different brand to blown ones).
The system was installed by an electrician so I assume it was specced correctly but I am wondering if I need a bigger RCBO or if the RCBO is faulty or if something else is amiss.

Thank you.

 

[Baddegg]

That’s a strange one…..one thing you definitely don’t want to do is put a bigger rcbo in!…can’t imagine the new spots would make a difference….where did you get them? Have you tried removing just the new ones only and reenergising?…

 

[Lister1987]

Only thing can yhink of is high inrush possibly? Switch to a C curve and see if the issue persists, could be a bad driver, bad lamp or a combination

 

[Dartlec]

Hello - I wonder if anyone can give me some advice about the following:

My house has two outside lighting circuits (front lights and back lights). These are controlled via separate switches which are connected to a 6amp RCBO (30mA B curve) in the CU. Each circuit has 20x GU10 LED spots at 5w each. So each circuit is around 100w. (total 40 spots/200w). If I switch both front and back lights on the RCBO trips after 10 seconds - every time. If I just switch on one circuit (either front or back) the RCBO does not trip. This is relatively new behaviour - in the past I have had both front and back lights on with no issues. The only change is that I have replaced some blown spots (different brand to blown ones).
The system was installed by an electrician so I assume it was specced correctly but I am wondering if I need a bigger RCBO or if the RCBO is faulty or if something else is amiss.

Thank you.

Does the same trip occur if you turn on one circuit - wait a few minutes, then turn the other one on, or is it only if both are turned on together that things trip?

Are all the lamps functioning correctly when they are on, or are any seeming dim/flickering?

A larger RCBO won't solve the problem as you should be nowhere near a 6A limit at the moment.

High inrush is one possibility, in which case putting one circuit on, then waiting before putting the other one on, should work.

If it's not that, then the most likely is that either there are some connection or issues with fittings on both circuits, or all the lamps are 'leaking' to earth slightly.

There could be a slightly loose connection somewhere, which only shows up once energised, with the connections moving slightly due to heat. However, that would likely have to be the case on both circuits to cause the symptoms you are describing.

An electrician with the right tester could do some insulation resistance tests and confirm if there is a problem or not. They could also test the RCBO to ensure it's not just being over sensitive (Most RCBOs trip at about 25mA but a sensitive one might trip at 15-20mA)

If each circuit was leaking say 10-15mA due to poorly constructed fittings, then one circuit alone might not reach the limit but both added together might.

If so, and faulty fittings are ruled out, one option might be to add another 6A RCBO and split the circuits - that may or may not be simple depending on your setup.

 

[DPG]

Only thing can yhink of is high inrush possibly? Switch to a C curve and see if the issue persists, could be a bad driver, bad lamp or a combination

Can't be inrush though - it trips after a while, not on first switching on.

 

[Lister1987]

Can't be inrush though - it trips after a while, not on first switching on.

Faulty circuit components? Lagging the circuit? Drivers not kicking in fully?

 

[DPG]

Faulty circuit components? Lagging the circuit? Drivers not kicking in fully?

Surely he would have seen the fact that the lamps didn't go to full brightness until after a few seconds.

 

[Robert0911]

Does the same trip occur if you turn on one circuit - wait a few minutes, then turn the other one on, or is it only if both are turned on together that things trip?

Yes. Trip only occurs when both circuits are on regardless of delay in turning the other on.

Are all the lamps functioning correctly when they are on, or are any seeming dim/flickering?
YES
A larger RCBO won't solve the problem as you should be nowhere near a 6A limit at the moment.

High inrush is one possibility, in which case putting one circuit on, then waiting before putting the other one on, should work. This does not work. Trips with a 5 minute gap between circuit 1 and circuit 2 being turned on

If it's not that, then the most likely is that either there are some connection or issues with fittings on both circuits, or all the lamps are 'leaking' to earth slightly.

There could be a slightly loose connection somewhere, which only shows up once energised, with the connections moving slightly due to heat. However, that would likely have to be the case on both circuits to cause the symptoms you are describing.

An electrician with the right tester could do some insulation resistance tests and confirm if there is a problem or not. They could also test the RCBO to ensure it's not just being over sensitive (Most RCBOs trip at about 25mA but a sensitive one might trip at 15-20mA)

If each circuit was leaking say 10-15mA due to poorly constructed fittings, then one circuit alone might not reach the limit but both added together might.

If so, and faulty fittings are ruled out, one option might be to add another 6A RCBO and split the circuits - that may or may not be simple depending on your setup.

Thank you. Next step is electrician I think!

 

[Robert0911]

Thank you for all the replies! Just tested it again just now.

1. The back lights were on for about 5 mins I then turned on the front lights and the RCBO tripped out immediately. Reset it and turned just the front lights on. They stayed on.
2. Turned the front lights on - left for 5 mins, turned the back lights on, RCBO tripped immediately.
3. So this is a change to the behaviour I described earlier. (tripping after 10 secs). Now tripping instantly.
4. I can confirm that both front and back lights operate fine if one or the other is on.
5. I did disconnect the lamps where the bulbs had been changed but no difference.

So I think that I will need to get an electrician to come round. The CU is full so splitting the circuits will be expensive.

Thanks again.