Lighting circuit tripping RCD

[roy007]

Could anyone tell me why turning off the lights in my garage (3 x flurestence tubes) would trip the rcd on my split board. This lighting circuit is not protected by the rcd and it does not happing very often very intermittenly. The switching is two way.

[Hoggy57]

Strange one this! however here's a couple of ideas,
At first I thought that it might be due to the feed and neutral of the lights coming from opposite sides of the split board ie: the feed from the none rcd side say and the neutral from the rcd bus bar, presenting the rcd with an imbalanced load, but I’m sure this would cause a permanent fault.
The only other thing I can think of is the possibility of transients caused by switching the lights on/off. If the fittings are fitted with transient suppression capacitors, they will short the transients to earth. This might be picked up by the rcd if the current exceeded 30mA. Try taking a couple of tubes out to reduce transients and see how they perform. If this solves it you may need a 100mA rcd

[patspark]

do not change the rcd it is there and is 30mA for a reason your safety
take a look at the regs

[Hoggy57]

Agree with patspur regarding changing the rcd to a 100mA. Have now read the 16th edition regs and its a no no. Apologies