RCD keeps tripping once radiators cut in Wilo pump

[shelley]

Soon as I light the multifuel stove Arada 10.8kw,that runs 6 radiators and hot water.
We had it installed about 10 years ago, by a registered Hetas builder. Had no problems since then until now.
We are getting hot water, that runs on that backboiler,but when the control switch is on, it trips. So we switch the switch off,and use the hot water up.
Hubby who is a engineer, we have changed the thermostat, the pump Wilo Yonus Pica , but onto the same wilo connector ,so haven't changed that connector. It's getting frustrating now, house is getting real cold.Any advice would be welcome.We have managed to get another brand new pump now, and the black connector switch thats supplied ,as the one we got from Ebay reconditioned, can't garentee that's not a bump steer as no black switch. 

 

 

 

Edited November 21, 2023 by shelley
Photos

[GarethM]

Use the new connector on a short flex before deep diving elsewhere.

 

If the pump runs and doesn't trip the ring main you need to check the original connection and controls etc.

[Steven P]

If it cuts out straight away then that suggests an earth fault - a faulty connection somewhere, a short circuit or something - which might be something to do with age. If it takes a while to trip that could be overcurrent - the motor for example taking too much current and eventually it trips.

 

So earth fault. If you disconnect parts in sequence you should get to the part where it trips straight away. Disconnect the motor wiring, turn the power back on, if it trips then it probably isn't the motor. Go up a level, disconnect the thermostat and motor - a trip then it points towards the connector. If you disconnect the whole lot and it trips then that suggests the house wiring somewhere. A little time working out the fault will get you there and the part you might want to replace.

 

Obviously you will both know that mains electricity can have a nasty kick to it.... turn it off, prove it is off, before you reach for a screw driver.