On 15/12/2012 14:59, Caecilius wrote:
I've been experiencing occasional nuisance RCD tripping for a few
years now. It's very occasional - sometimes going for up to six
months without tripping. On average I'm getting a trip around once
every two months.

I've done some equipment testing with a megger and basic RCD
sensitivity testing with some home-made leakage plugs (plugs with
resistors between live and earth to give a known leakage current).
Based on this, I think my RCD is over sensitive.

My plan is to replace the RCD, which is fairly cheap and simple. But
I'd like to test the old one and the new one with something better
than leakage plugs to see if there's any change in sensitivity.

Does anyone know if it's possible to hire RCD testers for short
periods at a reasonable rate? When I've looked, most hire shops
direct me to a PAT tester which isn't what I'm looking for. I don't
want to buy one for a single project.


You can buy affordable clamp meters where if you can pass just the live
and neutral through the clamp together you can measure residual current
directly. Depending on supplementary bonding you can also get an
indication by measuring the current flowing in the protective conductor.
You might then be able to find the offending circuit.

As others have suggested, each appliance does have an allowable leakage
and combined it may be close to the RCD limit.

Moving some circuits on the non-RCD portion whilst using RCBOs on the
most likely offending circuits like the kitchen circuit may solve the
problem.