My GSHP trips 32A MCB

[nowty]

How come you have a 32A MCB and even a 63A MCB tripping, caused by condensation you think, but not the RCD??
That doesn't sound right to me?

Desp

I must admit that is something I don’t understand, the pipes, the water pumps, the compressor and the heat pump housing are all earthed and even a bit of water is unlikely to trip a 64A mcb. Either something else is wrong which will become evident within a few days or the failed water pump was occasionally internally short circuiting.

[spread-tee]

Hmmm, I take it you have tested the RCD? they are pretty reliable but you never know. We've had some bother with the Hagar ones recently-ish, the little flying earth lead was an issue once IIRC.

Desp

[AE-NMidlands]

I must admit that is something I don’t understand, the pipes, the water pumps, the compressor and the heat pump housing are all earthed and even a bit of water is unlikely to trip a 64A mcb. Either something else is wrong which will become evident within a few days or the failed water pump was occasionally internally short circuiting.

Are they just earthed, or cross-bonded too?
A

[Stinsy]

I don’t think it is the condensation shorting live to earth. That would trip the RCD as small current leaks to Earth but I wouldn’t expect that to pull enough current to trip an MCB (particularly 32A/64A). Seeing as you have redundant pumps could you deactivate them, one at a time, to test if one is causing the nuisance trip?

[nowty]

The earth from the consumer unit is terminated in the heat pump, then various earths go to the water pumps, compressor casing and metal housing.

I have tested the RCD in terms of pressing the test button but today I am going to give it the nuclear test by shorting a live cable with a 1A fuse and a 100 ohm resistor in series to various parts of the heat pump installation.

I am just waiting on the heat pump finishing its current heating cycle before I conduct the tests.

[Joeboy]

The earth from the consumer unit is terminated in the heat pump, then various earths go to the water pumps, compressor casing and metal housing.

I have tested the RCD in terms of pressing the test button but today I am going to give it the nuclear test by shorting a live cable with a 1A fuse and a 100 ohm resistor in series to various parts of the heat pump installation.

I am just waiting on the heat pump finishing its current heating cycle before I conduct the tests.

Once you've got it sorted, have a crack at the 111 grease bag. No moisture will get in.

[nowty]

The earth from the consumer unit is terminated in the heat pump, then various earths go to the water pumps, compressor casing and metal housing.

I have tested the RCD in terms of pressing the test button but today I am going to give it the nuclear test by shorting a live cable with a 1A fuse and a 100 ohm resistor in series to various parts of the heat pump installation.

I am just waiting on the heat pump finishing its current heating cycle before I conduct the tests.

Once you've got it sorted, have a crack at the 111 grease bag. No moisture will get in.

I cannot do the grease bag thing as the electronics are open to atmosphere via a grill surrounding the body of the pump. I would prefer to mount the pump upside down so any condensation does not drip down the housing through the air grill, but the instructions forbid mounting it that way.



Anyway conducted my improvised RCD test using a live wire to touch just about every point on the heat pump installation and the RCD trips every time so the RCD is functional. Its been 36 hrs now since I changed the failed water pump and no MCB trips so far. Probability is growing that I've fixed it.

[Fintray]

I cannot do the grease bag thing as the electronics are open to atmosphere via a grill surrounding the body of the pump. I would prefer to mount the pump upside down so any condensation does not drip down the housing through the air grill, but the instructions forbid mounting it that way.


Anyway conducted my improvised RCD test using a live wire to touch just about every point on the heat pump installation and the RCD trips every time so the RCD is functional. Its been 36 hrs now since I changed the failed water pump and no MCB trips so far. Probability is growing that I've fixed it.

Would it be possible to remove the electronic control section of the pump from the body and just run some cabling to a suitably dry position?

[Stinsy]

BTW I'd recommend a 10kΩ resister rather than a 100Ω. It is a better test of the RCD pulling 230mA rather than 2.3A!

[nowty]

BTW I'd recommend a 10kΩ resister rather than a 100Ω. It is a better test of the RCD pulling 230mA rather than 2.3A!

I think you mean a 1kΩ resister, but anyway the 100Ω resister was the only one I could find but I did have a 1A fuse in the plug it was running from, just in case.

I did say it was a nuclear test of it !