Air source heat pump keeps tripping rcd

[anonfool72]

Hi all,

Sorry if this is the wrong sub forum to ask.

Our heating system started tripping the rcd. Do we need to call an electrician or a heating engineer to have a look? The sequence of events is: turn on the rcd, control units light up, after a second trips the rcd. Its a air source heat pump system (overly complicated & near impossible to understand).

thanks

 

[SUNRAY]

Hi all,

Sorry if this is the wrong sub forum to ask.

Our heating system started tripping the rcd. Do we need to call an electrician or a heating engineer to have a look? The sequence of events is: turn on the rcd, control units light up, after a second trips the rcd. Its a air source heat pump system (overly complicated & near impossible to understand).

thanks

You require someone who understands the heating system, a lot of electricians don't.

 

[oldbutnotdead]

Is the RCD protecting other circuits as well as the ASHP? If yes then first job is to disconnect all loads from the other circuits (switching off MCB or pulling fuse is not enough, you need to disconnect neutrals as well as phase cables) then check for function.

 

[anonfool72]

So I narrowed down the problem. It's due to an underfloor heating actuator -or- an underfloor heating pump. Here's what Ive done:

- There are 3 control boxes that power the ufh actuators & pumps, 2 downstairs and 1 upstairs.
- I disconnected power from them one by one and the 2nd box is where the problem is (attached pic)
- Since RCD trips on current leakage to ground I'm guessing a faulty actuator or pump makes sense, i.e. exposed coil makes contact with the water & leaks current?

If I feel adventurous I'll disconnect the power to the actuators one by one till I find the faulty one (somehow I'm convinced it's an actuator and not a pump) but at least I can turn the heating on now for the rest of the house and more importantly have some hot water!

 

[Adam_151]

If I feel adventurous I'll disconnect the power to the actuators one by one till I find the faulty one (somehow I'm convinced it's an actuator and not a pump) but at least I can turn the heating on now for the rest of the house and more importantly have some hot water!

My money is on the pump!

 

[Johnmdc]

It's more likely to be the pump because the actuators only have live and neutral to them, they don't have an earth, so are unlikely to trip the RCD.

 

[anonfool72]

Makes sense -- It's easier to start with the pump so I'll try that first tomorrow.

 

[anonfool72]

I have an update, as expected I was completely wrong.

My perception was that only the heating system was affected by the RCD tripping (everything else in the house was just fine) which lead me to believe it was the cause of the problem. It's not.

The RCD also protects the external lights (patio & driveway) and one of them was filled with rainwater. I should have turned off the heating system via the main isolation switch and tested the RCD before jumping to conclusions.
The fact that I disconnected a ufh control box and it all worked was purely coincidental (basically it stopped raining).

 

[oldbutnotdead]

Is the RCD protecting other circuits as well as the ASHP? If yes then first job is to disconnect all loads from the other circuits (switching off MCB or pulling fuse is not enough, you need to disconnect neutrals as well as phase cables) then check for function.

Mmmmm

 

[anonfool72]

This is a follow-up..

I identified the light that caused the issue & isolated the circuit (there is no switch for the light, just an MCB and a PIR).

I know it sounds simple to replace a light, but this proved to be a pain, see photo attached.

It is a ground spotlight embedded in resin (!) and seems impossible to remove. I tried my best and was careful to remove all the stones/ resin round the edge (some of it was over the light cover).
I removed the screws but the cover itself seems stuck. I tried pulling, hammering and using a screwdriver as lever (and breaking it..) nothing worked.

Anyone has any ideas how to remove the cover or the whole light? By the way, it seems one of the cover bolts spins freely so the whole enclosure will probably need replacing. I suspect that was the cause of the leak.

Thank you!