In the last year or so I’ve had some tricky RCD nuisance tripping faults to diagnose and resolve. Normally with these kind of faults, there is an obvious fault on one of the circuits when tested, particularly an insulation resistance fault which causes sufficient current leakage to earth which is potentially dangerous as it can lead to electric shocks when metal appliances, sockets, switches etc are touched. RCDs are specifically designed to guard against this type of fault, better than regular fuses can.
In 3-4 cases recently however, customers have reported intermittent nuisance tripping of consumer unit RCDs, which then generally can be reset after tripping. Yet I can see no obvious fault when I call round to test the affected circuits. I have noticed that the circuit insulation resistance readings are usually not perfect, but still in the acceptable range (older wiring and connected appliances often show a deterioration in insulation resistance, very few properties ever give an ideal result). The RCDs themselves always test OK for tripping current and speed, so it’s a bit of a mystery in these cases.
In some cases, after a few visits without any luck finding the problem using normal tried and tested diagnostic methods, I have replaced the RCD unit itself as a last measure, despite no obvious problem with it. Rather unexpectedly, this appears to have resolved the nuisance tripping problem in all these cases!
So I think what is happening in these cases is that the RCD function is being compromised by some earth leakage in the electrical installation (normally not enough to trip a healthy RCD) and that in some instances, they are deciding to trip when they shouldn’t.
It may well be that with increasing use of LED lighting, electronic devices & appliances, wireless routers, smart TVs, etc in the home, the combined capacitive effect of all these is raising the background earth leakage on the system, this constant low level may be causing some RCDs to malfunction over time. Interestingly, there is some evidence on the internet now that this may be a growing issue in homes.
So, if you have a stubborn & intermittent RCD fault in your home, give us a call, replacing the RCD may be the answer if all else fails.