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

Thanks
Adrian

"Adrian Brentnall" wrote in message
...

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?

Some can do.

Am I seeing an MCB failure, rather than a heatpump failure?

Only way to be sure is measure its power use or
swap the MCB and see if that fixes the problem.

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

No way to say for sure without measuring or swapping the MCB

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

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



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

Thanks
Adrian



--
Religion is regarded by the common people as true, by the wise as
foolish, and by the rulers as useful.

(Seneca the Younger, 65 AD)

On Mon, 3 Feb 2020 19:48:05 +1100, Ray, better known as cantankerous
trolling senile geezer Rodent Speed, wrote:

So - do MCBs age over time?

Some can do.

LOL Brilliant, senile idiot!

--
Marland answering senile Rodent's statement, "I don't leak":
"That¢s because so much **** and ****e emanates from your gob that there is
nothing left to exit normally, your arsehole has clammed shut through disuse
and the end of prick is only clear because you are such a ******."
Message-ID:

On 03/02/2020 08:48, Ray wrote:
"Adrian Brentnall" wrote in message
...

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?

Some can do.

Thanks - that's what I was reading on the 'net


Am I seeing an MCB failure, rather than a heatpump failure?

Only way to be sure is measure its power use or
swap the MCB and see if that fixes the problem.

I know that the 'running' current for the heatpump is around the 10 -
13A range, but I remember that a standard 20A MCB would trip out on the
initial switch-on current, when the compressor starts - which is why
they fitted a type 'D' - 'slow-blow' MCB in the first place.


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

No way to say for sure without measuring or swapping the MCB

Yes - I think MCB-swapping is a good place to start.
Now just got to find a supplier that has some in stock.
Thanks
Adrian

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

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



I would expect ageing to occur faster if held close to the maximum
current for long periods or in an overheated CU ie between two heavily
loaded MCBs.

What's the MCB you require? There might be one on the shelf at work and
if there is one you can have it almost free if you want it - P&P costs
must be donated to charity....

--
Adam

On 03/02/2020 18:55, ARW 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 have a call into the local engineers anyway - but just wondering...
I'd rather replace an MCB than a heatpump!



I would expect ageing to occur faster if held close to the maximum
current for long periods or in an overheated CU ie between two heavily
loaded MCBs.

What's the MCB you require? There might be one on the shelf at work and
if there is one you can have it almost free if you want it - P&P costs
must be donated to charity....


That's very kind of you Adam - but the narrative has moved on from this
morning..

Drove to the wholesaler in the next-town-but-one - collected a couple of
D20 single-pole MCB's.
Got back home, all cocky, like - installed a new MCB and the darn thing
wouldn't run for more than a few minutes.
In fairness, wholesaler fellow said it was quite possible that the MCB
could have been the problem - it just wasn't..

Decided to apply a bit of science (perhaps a bit late!) and measured the
current into the heatpump at 35A (!) - which would explain why the MCB
was tripping.. - should have been nearer 13A.

Contacted the heatpump guys, under instruction from them checked the
current to the 'motor run' capacitor - which was 9/10 of sod-all.. and
should have been somewhere in the 6A range.
Other diagnostic was that the compressor sounded to be running a bit
'rough'.

Drove back to the next town and collected a new 50ufd / 400v motor run
capacitor from the heatpump guys. Swapped it in, and the meter showed 6A
through the capacitor and 12 - 13A to the entire unit.

Problem seems to be solved..
Heat-pump supplier pleased that it's fixed, regretful that he can't sell
me a new compressor!

Thanks everybody - and particular thanks to Adam for the generous offer...

Adrian Brentnall wrote:

the meter showed 6A through the capacitor and 12 - 13A to the entire unit.

What size of house are you heating with a 3kW heatpump?

Even with a COP of say 4, then 12kW output sounds low relative to an
"average" 24 to 30kW combi-boiler.

Sounds like a small heat pump what does it actually achieve?
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Adrian Brentnall" wrote in message
...
On 03/02/2020 18:55, ARW 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 have a call into the local engineers anyway - but just wondering...
I'd rather replace an MCB than a heatpump!



I would expect ageing to occur faster if held close to the maximum
current for long periods or in an overheated CU ie between two heavily
loaded MCBs.

What's the MCB you require? There might be one on the shelf at work and
if there is one you can have it almost free if you want it - P&P costs
must be donated to charity....


That's very kind of you Adam - but the narrative has moved on from this
morning..

Drove to the wholesaler in the next-town-but-one - collected a couple of
D20 single-pole MCB's.
Got back home, all cocky, like - installed a new MCB and the darn thing
wouldn't run for more than a few minutes.
In fairness, wholesaler fellow said it was quite possible that the MCB
could have been the problem - it just wasn't..

Decided to apply a bit of science (perhaps a bit late!) and measured the
current into the heatpump at 35A (!) - which would explain why the MCB was
tripping.. - should have been nearer 13A.

Contacted the heatpump guys, under instruction from them checked the
current to the 'motor run' capacitor - which was 9/10 of sod-all.. and
should have been somewhere in the 6A range.
Other diagnostic was that the compressor sounded to be running a bit
'rough'.

Drove back to the next town and collected a new 50ufd / 400v motor run
capacitor from the heatpump guys. Swapped it in, and the meter showed 6A
through the capacitor and 12 - 13A to the entire unit.

Problem seems to be solved..
Heat-pump supplier pleased that it's fixed, regretful that he can't sell
me a new compressor!

Thanks everybody - and particular thanks to Adam for the generous offer...

On 03/02/2020 21:20, Brian Gaff (Sofa 2) wrote:
Sounds like a small heat pump what does it actually achieve?
Brian

It heats our (fairly) small house quite nicely!

Very happy with it - when it's working well - which, over the last 15
years has been most of the time.

Sucks heat out of the ground via 3 x 100m coils of plastic pipe buried
under our polytunnel and produces circulating central heating water to
feed our radiators.

The manufacturer reckons that the system produces 3 - 4kw of heat for
every kw of electricity consumed.

On Monday, 3 February 2020 22:13:23 UTC, Adrian Brentnall wrote:
On 03/02/2020 21:20, Brian Gaff (Sofa 2) wrote:
Sounds like a small heat pump what does it actually achieve?
Brian

It heats our (fairly) small house quite nicely!

Very happy with it - when it's working well - which, over the last 15
years has been most of the time.

Sucks heat out of the ground via 3 x 100m coils of plastic pipe buried
under our polytunnel and produces circulating central heating water to
feed our radiators.

The manufacturer reckons that the system produces 3 - 4kw of heat for
every kw of electricity consumed.

You have to include the electricity used in the various pumps/fans round the system.
Looks a lot less good then.

You can get to the point where off-peak storage heaters are more economical.

Storage heaters need virtually no maintenance and are much much cheaper to install. And more reliable (no moving parts except possibly a fan.

There were lots of cowboy installers around in the early days of heat pumps too.

On 03/02/2020 20:08, Andy Burns wrote:
Adrian Brentnall wrote:

the meter showed 6A through the capacitor and 12 - 13A to the entire
unit.

What size of house are you heating with a 3kW heatpump?

Even with a COP of say 4, then 12kW output sounds low relative to an
"average" 24 to 30kW combi-boiler.


I had my house which is pretty big assessed and they reckined that 10Kw
would run it and its been on a 12Kw boiler since built.

Its insulated to 2000 specs...

--
Of what good are dead warriors? €¦ Warriors are those who desire battle
more than peace. Those who seek battle despite peace. Those who thump
their spears on the ground and talk of honor. Those who leap high the
battle dance and dream of glory €¦ The good of dead warriors, Mother, is
that they are dead.
Sheri S Tepper: The Awakeners.

In article ,
harry scribeth thus
On Monday, 3 February 2020 22:13:23 UTC, Adrian Brentnall wrote:
On 03/02/2020 21:20, Brian Gaff (Sofa 2) wrote:
Sounds like a small heat pump what does it actually achieve?
Brian

It heats our (fairly) small house quite nicely!

Very happy with it - when it's working well - which, over the last 15
years has been most of the time.

Sucks heat out of the ground via 3 x 100m coils of plastic pipe buried
under our polytunnel and produces circulating central heating water to
feed our radiators.

The manufacturer reckons that the system produces 3 - 4kw of heat for
every kw of electricity consumed.

You have to include the electricity used in the various pumps/fans round the
system.
Looks a lot less good then.

You can get to the point where off-peak storage heaters are more economical.

Storage heaters need virtually no maintenance and are much much cheaper to
install. And more reliable (no moving parts except possibly a fan.


Those things are a Pile of poo removed more of them that i care to
remember!...


There were lots of cowboy installers around in the early days of heat pumps too.

--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.