On 03/02/2020 08:57, The Natural Philosopher wrote:
On 03/02/2020 08:24, Adrian Brentnall wrote:
HI Folks

Our domestic central heating is run by a ground-source water heatpump
- most of the time this is very successful, it was installed about 12
years ago.

In the last 24 hours, the MCB that feeds the heatpump circuit has been
tripping out. When it's manually reset, the heatpump fires up again
and runs.. until it trips out again.

Wiring is as follows
Main CU has a D40 MCB that feeds a smaller CU in the workshop, where
the heatpump is housed. A D20 MCB in this smaller CU feeds the
heatpump - which is nominally 3kw, but takes a big switch-on current.

As I say, this has all worked well for the past 12 years - until last
night.

So - do MCBs age over time? Am I seeing an MCB failure, rather than a
heatpump failure?

I'ts a lot cheaper to replace to see...

That's what I was thinking. Need to find a local supplier with some in
stock... thanks

Can we confirm this is not in fact an RCBO and earth leakage is not
involved?

Yes - it's an MCB


MCBS can age. But 12 years is not long...

The heatpump itself is rated 3kw, but takes a fair 'over-current' when
the compressor kicks in. Initially the installer had a standard 20A
breaker on there, but that kept tripping, which is why the Type D MCB
was installed.

Thanks
Adrain



I have a call into the local engineers anyway - but just wondering...
I'd rather replace an MCB than a heatpump!

Thanks
Adrian