My GSHP trips 32A MCB

[nowty]

Oh dear, around midday I found my display for my heat pump blank and found the 32A MCB tripped (but not RCD), never done that in the 3 years its been running. I was hoping it was a one off as when I reset it, it started working ok for the rest of the day, water pumps all working fine and all temperatures ok, gas pressures ok. But MCB tripped again this evening so its staying off for now and unfortunately the gas at Nowty Towers is back on, good job I did the service on gas boiler only a few days ago.

I'm hoping its the starting capacitor failing which should be an easy fix, so a fun day will be had tomorrow investigating.

[Stinsy]

That is bad news, particularly as it is due to (finally) get cold next week.

• Do you have a spare MCB? Could you swap the MCB with another with the same rating in the CU? The first thing I’d like to eliminate is faulty MCB.

• The next thing I’d look at is the ground-loop and it’s pump. Is the fluid level correct? Is the pump bled. Can you run the pump independently of the rest of the system?

• Now check the Capacitor. Is it swollen, leaking, or otherwise showing sign of failure? If you remove it from the HP, momentarily short the terminals with a piece of wire, then set your multimeter to measure resistance, you can expect the display to show a reading for a few seconds before returning to “open circuit”. If it only reads “open circuit” or shows a reading indefinitely the cap is dead.

• After that you’ll need an f-gas engineer to replace the compressor…

[Stan]

Might be showing up a faulty rcd Nowty as well as the more obvious problem.

[Joeboy]

Might be showing up a faulty rcd Nowty as well as the more obvious problem.

Hopefully this.

[marshman]

Does the compressor have a "soft start" box of electronic "magic". Mine does but it is a bigger unit than yours. These tend to have a "shortish" life.

[Ken]

Yes soft start is a real pain. I have got through a few chop saws because of it. It is probably only one underated bit but for hapfarth of tar .....

[Stinsy]

Yes soft start is a real pain. I have got through a few chop saws because of it. It is probably only one underated bit but for hapfarth of tar .....

I've always moaned about my 9" angle grinder. I got the Makita one without "soft start" because the one with "soft start" was out of stock. It tries to rip itself out of my hands every time i turn it on. But I've been told the one without "soft start" lasts much longer.

[marshman]

__

[nowty]

Been looking at the heat pump problem this morning.

So my RCD is working correctly and the fact that the RCD did not trip is a good sign as any shorting of the compressor windings to earth would probably be terminal.

I don't think it has a soft start.

I was not convinced about the MCB being faulty, I thought they were pretty bullet proof, however, maybe not.

Took the cover off the heatpump to see the general condition of it and still looks like almost new.

Then looked at the electronics to see the state of the starting capacitor and that looked fine but I took it out for a proper check.




I did not realise my multimeter has a capacitor function and that read almost the 50uF rating. I also checked the resistance and that started at about 25 mega ohms and was slowly rising so the capacitor is fine.



As I said in my first post, when the heat pump was running yesterday even after the first MCB trip, the water pumps were working, the temperatures were fine and the gas pressure gauges were showing normal. It also sounded normal, nothing unusual.

So I'm back to the 32A type B MCB. The heatpump is also protected by a 13A fused spur which did not blow so maybe the MCB was a bit premature on start up. Maybe its aged, or the compressor has aged and has slightly increased its start up current. Maybe I need to use a type C MCB as some websites suggest. Anyway I do have some spare 32A MCBs which are more modern than the existing one, so I replaced it for good measure.

Turned the heatpump back on and its been on twice working fine without tripping the new MCB. So either I have fixed the problem with the replacement MCB or if it happens again I'll try fitting a type C MCB, as the 13A fuse would blow anyway if there was a serious problem.

So gas boiler switched off again but used 38kWh of the dirty fuel since last night.

[Stinsy]

Been looking at the heat pump problem this morning.

So my RCD is working correctly and the fact that the RCD did not trip is a good sign as any shorting of the compressor windings to earth would probably be terminal.

I don't think it has a soft start.

I was not convinced about the MCB being faulty, I thought they were pretty bullet proof, however, maybe not.

Took the cover off the heatpump to see the general condition of it and still looks like almost new.

Then looked at the electronics to see the state of the starting capacitor and that looked fine but I took it out for a proper check.




I did not realise my multimeter has a capacitor function and that read almost the 50uF rating. I also checked the resistance and that started at about 25 mega ohms and was slowly rising so the capacitor is fine.



As I said in my first post, when the heat pump was running yesterday even after the first MCB trip, the water pumps were working, the temperatures were fine and the gas pressure gauges were showing normal. It also sounded normal, nothing unusual.

So I'm back to the 32A type B MCB. The heatpump is also protected by a 13A fused spur which did not blow so maybe the MCB was a bit premature on start up. Maybe its aged, or the compressor has aged and has slightly increased its start up current. Maybe I need to use a type C MCB as some websites suggest. Anyway I do have some spare 32A MCBs which are more modern than the existing one, so I replaced it for good measure.

Turned the heatpump back on and its been on twice working fine without tripping the new MCB. So either I have fixed the problem with the replacement MCB or if it happens again I'll try fitting a type C MCB, as the 13A fuse would blow anyway if there was a serious problem.

So gas boiler switched off again but used 38kWh of the dirty fuel since last night.

Failed MCB is the best possible outcome, easy fix plus only costs about £4. That's why I suggested it as the first thing to check!

I notice you have a clamp meter does it have "max current" setting? If it does you can clamp it somewhere convenient, leave it for a few days, and it'll tell you the highest current level measured over that period.