RCD tripping only when high draw device and lighting ring is on.

[Gooberstank]

Hi.

Wondering if anyone had any idea what might be happening. Last night I damaged a pendant light fitting by accident, not enough to stop it working.
However later in the evening when my car charger started at 11:30PM the whole house RCD tripped.
I only thought back to the light accident as the one thing that had changed and sure enough when I turn the breaker off which controls the light ring the pendant was on the car charger works.
After fault finding the oven has the same issue, it seems when a high draw device like an oven or car charger turns on the whole house trips, but only if the lighting breaker is on. Turn it off and everything works without tripping.
The main breaker is on the right side of the board and the car charger & oven ones are to the left of the lighting ring in case that has any bearing.
I’m totally stumped why that light circuit being on makes the house trip only when I use the oven or car charger.

Worth mentioning I removed the pendant light and rewired it in and like before the accident it works fine but the tripping is still happening.

Any ideas what might be going on?
Thanks.

 

[Avo Mk8]

RCD's tripping with a combination of loads is typically because those loads, plus probably other devices on the circuit, all have a small leakage current to earth, and the currents added together becomes enough to trip the RCD.
It's common for oven elements to have a bit of leakage, especially if they haven't run for a while and/or the element has absorbed a bit of moisture.
It sounds as if your light fitting may have an unusually high leakage current, ie a low insulation resistance between L and E.
You might try taking the bulb(s) out of the light fitting, and if the tripping stops, you definitely have an issue with the bulb or fitting. If that doesn't stop it, the problem is probably with that lighting circuit wiring,
An electrician would have an earth leakage/ insulation resistance tester and should be able to locate a fault of this sort.

You might also have other devices plugged in that contribute to this leakage. Electrical and electronic devices often have interference suppressors in them, typically generating up to 1mA of leakage per device, so the odd phone charger, laptop or tablet charger, radio, TV, washing machine, etc kept plugged in, even if the device is not on/running, all contribute to the total leakage that can become enough to trip an RCD.
An all RCBO consumer unit would generally avoid this issue.

But it sounds like your light fitting, bulb or the wiring still has a problem, even after your repair.

 

[James]

My guess is an earth to N fault in the damaged light fitting.
This will become a problem when other devices draw large currents.