Hombrey, (As an aside) You're not completely barking up the wrong tree regarding SP/DP switching on an RCD circuit, as even a clapped-out, tardy DP device can cause problems in certain cases - but it's not that common and there are so many similar installations that remain trouble free - so you should perhaps look elsewhere. If the IR test for the pump was OK, check for other likely faults on other equipment including loose connections to the fixed wiring, because the act of switching off at that point could be triggering something else. The point raised about DP isolation isn't an issue here, as you're using a plug-in timer, and for all we know the socket outlet might have a DP switch as well. Marj.
I who know nothing would first change the switch to DP one. And it would not surprise me if it sorted the problem. Surely it's the only logical first step to try ? Mr. HandyAndy - really
did you read bojs post andy, its on a plug mate, plug is a dp isolator, its the pump, its the pump, its the pump, im off to play squash. xxxxxxxxxxxxxxxxxxx
plug does satisfy double pole isolation, but my query regarded single/double pole switching of a motor and its possibility of tripping RCD
did you read bojs post andy, its on a plug mate, plug is a dp isolator, its the pump, its the pump, its the pump, im off to play squash. xxxxxxxxxxxxxxxxxxx How would a motor that has now been isolated by a switch or timer, trip a RCD ? Mr. HandyAndy - really
The motor does not get isolated, the phase is switched off. My query was if the fact that the neutral is still connected as the motor comes to a stop that it somehow imbalances the RCD. Not had this before just checking to see if any of you guys had experienced this, before i tell her that her pump is shagged, change the pump, then still have same problem. Thanks for all responses so far
Hombrey, Before handypandy starts yet another one of his pathetic rants about why he is right and everyone else in the world is wrong, completely loosing the plot of the original post please read this. I had exactly the same fault a few years ago. The pump turned out to be Italian, but imported by and fitted into a well known British made garden feature. I tried everything you have, and did change the pump. That made no difference. The tripping of the Rcd appeared random, about 75 % of the time. I never solved the problem. Luckily the 30ma Rcd only fed the pump and some lights around it, and was next to the 2 switches ( i even tried double pole). A 'expert' explained (and heres my simple version), that the pump was a magnetic drive type (no mechanical link between the rotors and the windings) and spun very freely. When powered down, coupled with the suppression capacitors the motor turned into a generator and that caused the rcd to trip. Obviously the double pole switch was closing one contact milliseconds before the other. I have also had similar faults with fluorescent lighting, Another last week. All i did was remove the capacitor and it solved the problem. explain how a capacitor (faulty or not) connected only between phase and neutral can trip a rcd ?
plug does satisfy double pole isolation, but my query regarded single/double pole switching of a motor and its possibility of tripping RCD Hombrey: I'm sure you're OK with the isolation issue, I put that in for JP's benefit as he wants to study the business. Regarding your SP switching theory, it's unlikely - otherwise every such installation in the land would suffer. So I refer you to the other points in my post. Marj.
plug does satisfy double pole isolation, but my query regarded single/double pole switching of a motor and its possibility of tripping RCD Hombrey: I'm sure you're OK with the isolation issue, I put that in for JP's benefit as he wants to study the business. Regarding your SP switching theory, it's unlikely - otherwise every such installation in the land would suffer. So I refer you to the other points in my post. Marj. But isn't a motor likely to have a residual current(which in this case would be on the neutral, as the live is disconnected) AFTER it is switched off, if only for a brief moment(enough to trip RCD) ? Mr. HandyAndy - really
Regarding your SP switching theory, it's unlikely otherwise every such installation in the land would suffer. But isn't a motor likely to have a residual current(which in this case would be on the neutral, as the live is disconnected) AFTER it is switched off, if only for a brief moment(enough to trip RCD) ? Not tonight Andy. I have a headache. Marj x
just keeping this topic in the last ten for a few more opinions, not that im disregarding any previous opinions, just would like all your inputs on this
Hombrey: I'm sure you're OK with the isolation issue, I put that in for JP's benefit as he wants to study the business. Marj got a problem with this pump affair..ok lets say the switched socket (disregard the timer) is infact SP (not DP) please read the following.. 1....A motor requires effective isolation of live and neutral via a DP switch and in the case of a bathroom fan motor sometimes TP to satisfy the regs. 2....Surely effective DP Isolation with ref to Hombreys pond pump motor (to satisfy the regs) cannot be gained with a plug plugged into the SP switched socket..the reason being that most of the time the pump would be switched off at socket for maintenance etc (people might not bother to pull the plug out) which in the case of the SP switched socket would not be effective isolation despite the fact that pulling the plug out would be effective isolation..so surely this is not allowable..Would not allow it myself and would insist on fitting a switched FCU..or as a last resort a DP switched socket. Anyway cheers Marj.
A modern 13 amp socket would be double pole switched and would be able to prove the theory of whether switching both Live and neutral would overcome the problem. The timer is likely single pole switched (to save pennies) So I would initially have the pump fed directly from the socket (after confirming it is double pole switched). If that stops the tripping you have proved the point otherwise it is a pump change. A pond pump will be a double insulated brushless induction type motor which will have capacitance to create stator/rotor magnetic fie;d phase difference. On switching off the motor can become a momentary generator however the winding would need a circuit to generate any current and that current should be balanced on the live and neutral and therefore wouldn't cause an imbalance to trip the RCD. As a cost free test try to feed from a double pole outlet and if that fails then the pump needs changing. The more I think about it the more convinced I am that the pump is leaking current to earth (terra firma) so that the neutral return current is less than the live supply current. I(live) = I(neutral) + I (leak)
If the fact the socket outlet is sp is upsetting you change for dp, its not a bank breaker is it. Jp the socket provides the required dp isolation, if someone cant be sacked to unplug then they deserve a crack, not that they will get one as long as it is in the phase, not bothering to pull the plug is a weak argument for non compliance. To repeat myself my cash is on the pump but i will mention this though, i was at theis scenario the other week with a freezer that was gonna be changed, just mucing around i noticed the rocker switch on the socket outlet was a bit rough, upon removal it was breaking down at it was indeed the culprit, this is pretty easy to diagnose to be honest, you should not struggle to isolate whats causing it.
Forums
Facebook
Twitter
You Tube
Instagram
Shop