Tripping RCD

[Rambler1]

Hi All,

I've got a 63A 30ma RCD in my garage / workshop which keeps tripping. The regular load on it is a standard domestic chest freezer with a 45W pond pump on a timer. The timer is set to switchthe pump on and off 6 times per 24hrs, each run period is 1.5hrs and they are equally spaced.

I have noticed that A) it doesn't trip during the frosty weather but now that its warming up it has started tripping again about once a month, later when it gets warmer it can trip as much as every day but not all the time, sometimes it will go for a week and then trip 2 / 3 times in a day. B) When I've been around to actually see/hear it trip I've noticed that it appears to do it on the power off part of the cycle.

If it was a dodgy connection or insulation I would have expected it to trip on the power on part of the cycle. I had a 60W pump on it and I changed for the smaller one but it made no difference. I've also checked all the connections but they seem ok. The cable on the pump is the original as supplied with it. I've isolated the freezer so that only the pump is on the circuit but it still tripped. I also changed the origional electronic/digital timer for an electro- mechanical cam type but its still the same. The pump is protected by a 5 amp line fuse which has never blown.

Any good ideas as to what it might be????

 

[Guest123]

Hi.

Have you tried an insulation resistance test of the fixed wiring in the shed???

Also tested the RCD itself at all - ramp test, trip times etc, could be that the RCD itself is faulty or the fixed wiring perhaps.

Have you tried the pump circuit as normal via the timer but with the actual pump disconnected???

 

[Rambler1]

Hi Lenny,

The pump, the wiring in the workshop and the RCD are all new and nothing else trips the RCD. The feed from the timer goes to a outdoor 4 way switch panel that only feeds the pump.

What puzzels me is the fact that it trips on the off part of the cycle, does this make sense?

 

[Madmole]

What puzzles me as a qualified Koi Healthcare Assistant is why anyone would turn a pond pump on and off like that. The filters will never establish the bacteria colony they require if the water flow keeps stopping. Only if there were no fish, or it was a huge lake would it not need filters

Pond pumps should be on 24/7 and never turned off for more than an hour max, the filter media must be kept wet at all times. It takes months to re-establish the bacteria if they diw off

Bit like the old myth of turning them off over winter and not feeding when its cold

At least its on an RCD, I see tons of ponds that arnt!

 

[blueman]

It seems that you have ruled out the freezer, pump and timer, althougth you could have more then one fault. So that leaves the fixed wiring and RCD itself. You could try replacing the RCD (I have seen them fail from new). Do you have any access to test equipment (IR tester etc)?

 

[Digster]

I agree with Lenny, Get an insulation resistance test done on all that you can in the circuit.
A tiny amount of earth leakage could slowly build up to 30mA it doesn't neccessarily instantly bang out.

 

[volt-dropping]

If the problem truly is seasonal then the bi-mettalics in an oversensitive protective device may be affected by ambient temp not to mention air humidity ingress.

When you mentioned you isolated the equipment did you mean unplugged as switching socket off still leaves rcd subject to certain fault conditions within the equipment.

As above-mentioned at a distance i would be looking at the rcd itself , when they are manufactured they are tested for operational disconnection not longetivity and can arrive on your doorstep ready to fail within a few days .

Only by disconnecting outgoing circuits from your garage consumer unit can you eliminate wiring and apparatus.

Good luck hope your fish aint belly up yet................