Pump tripped RCD - capacitor fell out when inspecting

Hi,

Not quite a central heating system but the same kind of pump used I believe.

It is used to increase the pressure of the water system when the tap is turned on.

Today it started tripping the RCD.

It is located on the roof below the exterior water tank.

I removed the plastic cover that covers the circuitry to look for damage. There was some evidence of moisture but as I inspected it the capacitor came lose and fell out.

Now I am unsure of the correct connections here. All I see is the ground, neutral and live coming into this box. Difficult to view as it located on the side next to the wall. There is an external switch (0,1,2) and also a flow valve below the pump.

How is the capacitor wired to the 3 connections in the box?

The body of the pump was quite hot, so not sure it has failed or it was just in the sun at that time of the day.

I think it is quite old, we moved in 3 years ago and the house is about 13 years old so could be original.

Any assistance would be appreciated.

I'm inclined to just buy a new one and fit it myself but if someone could point me in the direction of the capacitor wiring first or/and some simple diagnostic tests.

Thanks

The disconnected capacitor could conceivably blow a fuse or trip a MCB, but it wouldn't affect a RCD. For a RCD to trip, some of the current in the motor's winding is leaking to the frame, almost certainly because it has overheated and the insulation of the windings failed.
Chances are that the capacitor wires are a push fit into a couple of the holes on the left hand side of the third pic., but that's a guess, and I wouldn't recommend trying it.
The pump is similar to a central heating circulator, but these are usually made of cast iron, and rely on the water that they circulate being oxygen free, otherwise they would rust.
The version used for boosting water supplies, where the water contains dissolved oxygen, traditionally use bronze for the 'wet' parts, although plastics are used in cheaper pumps.

brianmoooore said:

The disconnected capacitor could conceivably blow a fuse or trip a MCB, but it wouldn't affect a RCD. For a RCD to trip, some of the current in the motor's winding is leaking to the frame, almost certainly because it has overheated and the insulation of the windings failed.
Chances are that the capacitor wires are a push fit into a couple of the holes on the left hand side of the third pic., but that's a guess, and I wouldn't recommend trying it.
The pump is similar to a central heating circulator, but these are usually made of cast iron, and rely on the water that they circulate being oxygen free, otherwise they would rust.
The version used for boosting water supplies, where the water contains dissolved oxygen, traditionally use bronze for the 'wet' parts, although plastics are used in cheaper pumps.

Click to expand...

Thanks. Yes I was guessing the cap wires were push fit in those holes. Impossible to get back in even if I knew where they went.
The capacitor came out when I was wiping some moisture from the area.

Any water causing a short would have certainly tripped the fuse and not just the rcd so makes sense what you said.


I assume the best and quickest fix would be just to replace the pump.

Many thanks

can you read the valueof the capacitor?

telectrix said:

can you read the valueof the capacitor?

Click to expand...

Yes sure
450Vac
8uF
50/60Hz

Yonny24 said:

Yes sure
450Vac
8uF
50/60Hz

Click to expand...

Just ordered a new one to arrive tomorrow

The rcd had been tripping occasionally the last year or two and never found the cause.
Could well have been this pump slowly on its way out.
It's used a lot and think it could be quite old now.

Bought the same model and brand so hoping it should be a simple swap. The new model is a little different in design.
Sprayed wd40 on the fittings so hopefully they should unscrew without issues. Fingers crossed

Had to shower in cold water today as this pump feeds a solar panel tank on the roof to assist in heating the water.

Thanks