Complex motor start cuasing RCBO to trip problem

[snowhead]

Anyone like my inductance idea?

No, Cumulative earth leakage is the answer.

 

[monkeyelectric]

Cumulative earth leakage looks the favourite for me too, have u a leakage meter?

 

[pmgd]

Snowhead: I agree that would seem logical. And I thought that for a while as well, however I cant square it with my observations. The total leakage of all annex connected equipment (excluding pump) is about 7mA. The leakage of the pump is zero (unless it is more at startup). The leakage of appliances on my ring main (where it works fine) I assume to be rather more than 7mA. *However - I will do this check to confirm*.

 

[pmgd]

monkeyelectric: I have an AC ammeter which I can insert into the earth lead of an individual applicance. I also have a device which does a similar job to a ramp tester. (It is a decade resitance box. Just keep adding in 1mA until it trips).

 

[lewlec]

Hi
Have you done any insulation resistance tests on the annex? Possibly N-E fault on a circuit, had this happen before and I know the these vsd's and rcds can be trouble some. If using a vsd with an rcd it should be of a b type really. Hope this is of use.
Regards
Gary

 

[monkeyelectric]

Looking at what you have done its either cumulative leakage or the startup current of the pump is overloading the rcbo when everything else in the annex is on aswell, you need a clamp meter really such as this TM-EL9809 High Resolution AC Earth Leakage Clamp Meter to test for both

 

[pmgd]

Thanks everybody for their help. I will go and do some more tests and repost the results in a few days. Hopefully they will show a smoking gun ... though I suspect not......

 

[Knobhead]

Given some of you’re test methods I think you would be better off getting an electrician in.

 

[pmgd]

Tony: You may be right - but I've done that twice .. and paid for 2 x 1 days rate with no appreciable advantage. If possible I want to be able to present any electrician with the 'smoking gun' so that he can take remedial action.

 

[monkeyelectric]

Tony: You may be right - but I've done that twice .. and paid for 2 x 1 days rate with no appreciable advantage. If possible I want to be able to present any electrician with the 'smoking gun' so that he can take remedial action.

To be honest if they were decent electricians it should be them finding the problem not you! What exactly did they do to try and resolve your problem in that day they spent looking?