elcb and borehole pump

mapj1

Thank you for your response. It is a RCD and whilst I no longer have measuring equipment I am familar with the basics of electrical installations and fault finding on them. I have already tried most of what you suggest.

Mike Lee MIET CEng

Andy

It doesn't have an earth spike. Everything is earthed to the earth provided by the supply company.

Mike

Hello everyone

Thank you very much for your reponses, which have been very helpful, not least in stimulating my own thinking. I'm pretty confident about the integrity of the house wiring and it seems that everything is pointing to the RCD as the problem. Whilst I tried the pump on two separate RCDs they are both of the same type, the same manufacturer and the same age of more than 20 years. I've emailed the manufacturer asking if their more modern versions are likely to cope better with, for example, the soft start electronics mentioned by Nathaniel.

If they don't respond or give a negative answer I will probably resort to hard wiring the pump as suggested by Andy Jewsbury. Fortunately the pump connection is only a couple of metres from the consumer unit and the wiring is in surface mounted plastic trunking.

In response to Andy B's concerns about the wiring to the RCD, it is top fed.

Thanks yet again for all your responses.


Mike Lee

Phone City Electrical Factors as Proteus is their own brand and ask if they are doing 30 mA Type A RCDs, I looked on their website and couldn’t see any, but the website may be out of date.


If you are swapping the RCD it would be advisable to swap from a Type AC to a Type A and would be one step towards updating the installation.


Andy Betteridge

Andy

I use CEF because they have a depot within a couple of miles of us. Their web site is a bit confusing, but I did find a full range of RCDs. Thanks for the tip about type A.


The borehole top-casing is plastic, so nothing to connect an earth to.

You maybe paying the penalty for having a 30mA RCD as a front end device. Others have speculated as to why it might be tripping but I think I would address that even if you do find a reason.

PROBLEM SOLVED?

Hello everyone

I received a very prompt and helpful response from Proteus wfich said "In recent years, additional surge arrestor components have been added to our RCDs to reduce the risk of nuisance tripping from transient events, similar to what you explain here.We found that with the introduction of larger capacitors in white goods appliances, a higher percentage of devices were suffering from this issue. By adding in the additional components, this has reduced this issue considerably, so it may well be that the older RCD is susceptible to nuisance tripping from the transients created by the new pump. So in answer to your question, I do think that you're experiencing nuisance tripping issues because the RCD is susceptible to the transients present in the new pump."

I have replaced the original RCD with an equivalent from their current range and (on the evidence of a few trial starts and a day's normal running) the new RCD doesn't trip on pump startup.

Just to address a couple of points made during the discussion, the new RCD is described as type AC but the spec says it responds also to pulsating DC fault currents which I think is a characteristic of type A. Also the installation instructions specify that it must be top fed.

Thanks yet again for all your help.

Mike Lee

Thanks for the update ... I hope it continues to work.  It's really appreciated that you provided this information, as it can be useful knowledge for future times.  I'd only seen it the problem on very old RCDs.  (And in one case I solved it in the way my EMC friends don't like, but simply removing a washing machine's filter.) 


Addendum:  the "pulsating dc" should indicate it's type A, not AC.  A picture on the front should show both a full-wave and half-wave sine shape for type A, or just the full-wave for type AC.  If the device itself says it's type AC, yet also somehow mentions sensitivity to pulsating dc, then I'm surprised.  But if the supplier writes nonsense on their website, I'm not surprised. There's a lot of confusion, and sometimes a new model becomes A instead of AC but doesn't get updated on the web.  It gets even worse for RCBOs, where there are letters for the MCB tripping characteristics (usually B or C) as well as the RCD type (usually A or AC, but could potentially be B).