Another RCD nusiance tripping question

[Norv]

Changed my CU about 2 months ago & did a complete test. (This is one of my assessment jobs). Unfortunately the whole house ring circuit is on 1 cb on the RCD side.

Over the last week the RCD has been tripping now & again. It does it mainly when the tv & cable box are switched on (washing machine & dishwasher are off). I unplugged the cable box this morning & left it off all day. The tv has been used during the day & the RCD hasnt tripped but I got home from work & put the kettle on & it tripped. I dont think its the kettle as its tripping when the kettle is off. I'm now thinking it might be the tv so I'll leave that unplugged tonight & keep the cable box switched on.

Anyone got any other ideas how I could find out whats causing the tripping.

Cheers

 

[RF Lighting]

Have you carried out an insulation resistance test on the circuit? If so what were the readings?

What other circuits are supplied by this RCD??

 

[Norv]

I carried out an IR test with my Megger. Unplugged everything in the house & the tests were >299M ohm

 

[JohnD]

Another possibility is aggregation of small leakages. Can you borrow a PATester? And try a clamp meter on the cores at the CU (incl the earth).

On PATesting, I've found it's the watery appliances that usually have earth leakages. Your mileage may vary.

PCs always have a bit of leakage, apparently because of the way their PSU works. I don't know if the cable box is the same.

 

[plugwash]

My guess would be that there are multiple loads that are leaking to earth and only when they are combined together and some bad luck (such as a surge) is added in to the equation.

The next step in troubleshooting this problem would be to use a PAT tester to get earth leakage measurements on all appliances.

 

[Norv]

I'll see if I can borrow a PAT tester from somewhere.

The RCD protects 2 cb's. The house ring circuit & the garage but there is nothing plugged in or switched on in the garage.

Fell asleep watching tv the other night & woke up about 2am & all the power had gone off. The only thing that was on when I fell asleep was the tv/cable box, bedside alarm clocks, combi boiler, fr/freezer & that was about it.

 

[JohnD]

boiler, you say?

water...bondd pipes...electric controls...pump...leaks...control board...drips

look there first. if it's on an RCD protected circuit, 5p says it's the culprit. sometimes the fault emerges when they cood down (whe hot, the drips evaporate)

edited: hee hee, beat you, Captain Plugwash!

 

[Norv]

Just to update you. The tv & cable box were plugged into a double adaptor. I've removed the adaptor & tripping has stopped. Needless to say I have binned it.