Pump wiring issue

[gazdkw82]

Connected up a showermate pump for a friend this evening. A plumber friend installed the pump a few months ago into the system, I just put a supply to it

Wired a FCU spur from a RFC socket in landing. Tested the circuit. All is good.

Energise the circuit. All good.

Open the tap to enable the point to run, RCD trips.

I knew it had to be something with tbr pump so I did a continuity test on it. There is continuity between neutral and earth. The cable is a pre wired flex.

Am I missing something, it's been a very long day....

 

[SparkyChick]

I guess there could be some kind of filter on the supply which may manifest as continuity (can't remember exactly how filters manifest - could be if you keep the tester connected for a while it will disappear as the caps in the filter charge and the current flow stops - I'm sure someone will correct me if I'm wrong).

But based on what you've said, if there is a connection terminal box or something similar I might be inclined to open it (if it doesn't void the warranty) and see if it's possible to test the windings of the motor separately.

If you've got an el clamp meter, I might see if there is excessive leakage on the RCD that trips, possibly ramp test it, but I think my focus would be on the pump. Possibly do an IR test at 250v... L-N, L-E and N-E, but if there is a filter this would skew the results.

 

[Timbo]

Could be a poorly wired flex in the pump, water in the terminal box or condensation.
Check flex for damage?

 

[SJD]

When you say there is continuity between N and E, exactly how many Ohms (or MOhms) did you measure?

Could well be faulty internal wiring or a short - I once had a new downlight from a well known brand with a N to E fault due to a screw having penetrated the N cable in the internal rubber potting compound.

 

[SparkyChick]

If you've got an el clamp meter, I might see if there is excessive leakage on the RCD that trips, possibly ramp test it

Just to clarify... there is obviously excessive leakage because it trips, but what I mean is to try and establish whether say the RCD trips at 26mA and without the pump it's sitting at say 25mA.

 

[buzzlightyear]

Open the tap to enable the point to run, RCD trips

water going through the pump.

 

[gazdkw82]

I didn't have a low ohms meter, just a meter to bell out.

I think the issue must lay with neutral to earth seems the rcd trips only when the tap is opened (enabling the pump to run). As soon as the pump tries to run (I.e a load) it trips RCD.

It's got neutral to earth written all over it?

 

[Timbo]

Most pumps use reed switches to switch relays to turn the pump on. Might be live to earth after the pcb inside. If N-E it might trip the rcd with a load on the RFC?

 

[marconi]

If there is a permanent N-E conductive path at the pump or in the new wiring you have done, then while the FCU is closed other loads might be expected to cause the RCD to trip when they switch on. Have you tried using a vacuum cleaner on the ring plugged in close to the point you spurred off to see if its starting surge causes the RCD to trip? If it does, open the FCU (FCUs are double pole) and see if the vacuum cleaner now causes the RCD to trip. Try turning on the vacuum cleaner a few times in each case of FCU closed/open. This little trial may gives you some pointers. (I assume the pump is functionally switched in the line only).

As an extra did you bond together the inlet and outlet pipes if they are metal with 4mm2 or thicker? If not there could be some strange earth leakage current flows when the pump is run because the inlet and outlet pipes are different potentials.