MCB Tripping on Lighting Circuit

[karlpestell]

Morning All

Im not an electrician but had one look into this issue last night and coming back tomorrow but was after a little advice/suggestions.

One of the MCB for the lighting circuit in the kitchen is tripping. The power feed comes direct from the MCB into a junction box where 3 sets of lighting are fed from. The electrician tested this connection and removed each of the 3 wires one by one and found that when the kitchen/outside light feed was removed from the junction box, the MCB was fine and didnt trip. Other lights are set 1 (single light in garage) and set 2 (3 x 240v downlighters in utility room)

Kitchen lighting is 10 x 240v downlighters (GU10 type). On the same feed are three outside lights (1 lantern style, 1 floodlight and 1 fluorescent round light).

The MCB seems to be tripping even if the lighting on this circuit is turn off and not used. Electrician seems to think it could be:

1 - Something has eaten through a wire (lots of evidence of rat droppings in loft space!) although couldnt see anything visible when looking last night.
2 - Something has got wet and causing an earthing issue (assume more the outside lights)
3 - Problem with one of the bulbs although not sure how if not turned on.

Any suggestions/help appreciated before I go mad!!

Also, the loft space above the garage is accessible but above the kitchen is a bedroom and bathroom so not sure how I can see broken without starting to pull up floorboards!!!

Thanks, Karl

 

[Jackrae]

What were the results of the insulation tests he did (you did say he was an electrician so he obviously would have done these to determine possible faults)

 

[JohnD]

have you looked at the outside light fitting yet for rainwater?

 

[karlpestell]

What were the results of the insulation tests he did (you did say he was an electrician so he obviously would have done these to determine possible faults)

Sorry, not something that he told me when discussing with him and I didnt ask for results (I've not had a lot of electrical knowledge so not the sort of question I would have thought of).

 

[karlpestell]

have you looked at the outside light fitting yet for rainwater?

Looked at the lantern and was fine but he is going to look at the floodlight next but at 10pm last night he didnt want to get the ladders off the van and annoy the neighbors.

 

[securespark]

It would be a delicious irony if the floodlight was flooded...

 

[JohnW2]

Are you sure that it's an MCB and not an RCD (or RCBO) (both identifiable by having a test button - a MCB does not have a test button) which is tripping? How frequently does this tripping occur?

Kind Regards, John

 

[PrenticeBoyofDerry]

If the outside lights prove to be fine. Then next place to look, would be heat damage to cables from downlights.
But I assume this issue has now been resolved!