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Nuisance RCD tripping

Postby Lawrence » Wed Nov 09, 2011 12:49 pm

my RCD is tripping intermittently. I have power circuits and a solar PV installation protected by the RCD. RCD tripped today with no change in load on the circuits i.e. fridge, freezer, TV (on standby) were all on and it tripped without any new load

do solar PV installations potentially cause RCD problems?

given it happens intermittently with no additional load, is this most likely to be a faulty RCD?
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Postby sparx » Wed Nov 09, 2011 6:48 pm

No reason why PV should give problem, it does need some extensive/expensive test equipment to test system and RCD so not really DIY.
If common RCD it may be a number of small leakages causing the trips, RCD's are quite reliable normally.
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Postby ericmark » Fri Nov 11, 2011 3:28 pm

I have two RCD's which are quite old so have not got anti-trip used in the expensive modern ones and I tend to get a batch of tripping may be once a week for a month then maybe two years before it trips again. This I consider as normal.

However there are items which it's hard to test and may have a fault causing tripping. Frost free freezers are a real pain as they have a timer which will activate the heaters which once trips auto resets so without dismantling the freezer is near impossible to check. The only way is to plug them into another socket powered from a different RCD and see if the fault swaps to the other circuit.

Even the compressor starting on a fridge or freezer can if it catches the wave form wrong cause the RCD to trip. Waiting until the fridge or freezer has warmed up a bit so it will run one can test with a PAT tester but because there may be a relay to test with an insulation tester may not find the problem. It needs to measure milliamp leakage rather than mohms to earth. Plus with a micro-processor using an insulation tester can blow it up.

As sparx says it can also be a build up of many things. In the past I have run extension leads from up-stairs sockets to see if it's a fridge or freezer. The washing machine is another problem anything with timers or relays is so hard to test without partly dismantling.

Unlikely to be TV as in the main they are class II. In other words they have no earth connection.
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