Household Electrics Tripping

[Paul FA]

I have garden lights in the front and back gardens. They are on a timer.
When the garden lights are on and the indoor house lights are also on, everything is fine.
When the Garden lights are on and I turn on the oven or ( occasionally) other large heating appliance, the entire property electrics trip. When I isolate the the garden lights (ie isolate them on the main switch board) everything works completely normal. The cooker works fine in the daytime and evening providing the Garden lights are not on. Please advise.

 

[SJD]

N to E fault, probably in the lighting circuit, the large load (on another circuit) causes enough current to bypass the RCD via this fault.

 

[Dartlec]

Sounds like you have a single RCD protecting the entire installation? How many circuits are involved?

Picture of the consumer unit may help advise further, but probably needs an electrician with suitable test equipment to test the circuits and track down the guilty party.

What you've managed to do so far will be very helpful in guiding where to test (garden lighting looks like the first place to check).

If you want to do more troubleshooting, If the front/rear garden lighting can be easily split then you could narrow it down to front or back and then carefully check wiring/junction boxes for water ingress or damage.

It does sound like a fault on the garden lighting - it may not be enough by itself to reach the limit and trip the RCD (It may be 15mA and the RCD might trip at 23mA, for example) - The cooker or other load may then add enough in combination with the lighting to trip the RCD.

Having a single up front RCD is not ideal for this very reason, so reconfiguring or upgrading the consumer unit with an RCBO for just your lighting circuit, or some or all of the other circuits, may be a good long term investment - depending on any test results you could seek advice or quotes on that if you want to be sure the problem tripping will not reoccur.

 

[timhoward]

It sounds like several factors all contributing a bit.
Heating elements are common for earth leakage especially if they are getting older.
Anything where water ingress is possible is another prime candidate for this kind of fault.
I was then typing similar stuff to @Dartlec, just read his very good post!
You are going to need someone with accurate test equipment unless there is an obvious cause.