P
panroller
I was asked at the weekend to have a look at a problem where an RCD keeps tripping.The installation is in a commercial lab where there are two split load boards (one RCD each), one supplying the offices and the other supplying the labs. The problem is on the board supplying the labs.
Having disconnected all the appliances from the RCD protected side of the board I IR checked all the circuits and found one ring main appeared a bit marginal so disconnected that circuit. This made little difference at first but after much experimentation I found that if the non RCD protected circuits were all turned off then the RCD would hold. When you turn the Non RCD circuits back on the RCD will trip again but there doesn’t seem to be any repeatable pattern as to when it will trip. There also seems to be a situation where, when it has tripped, it won’t reset unless you switch the main breaker off then back on again first.
I’ve checked the RCD (which is new since the problem appeared) and this all seems good. So that the lab can continue to work I have taken the RCD out of circuit. Having done this and re connected all the circuits everything stays on and all the Loop Impedance tests look good.
The owner of the business is back next week and I intend to go back and have another look with him as he was involved in the original build of the premises but I wondered if anyone had seen a problem like this and if you had any pointers as to what might be causing it.
Thanks in advance for your help.
By the way, as a new member I’ve already found some interesting info on the forum and I love the idea of being a ‘Junior Member’ I haven’t been a Junior anything for quite a while now!!
