Clive Long,UK wrote:
Roger,

I am coming to your way of thinking that is it the pump. When I
listen carefully to the pump it make a faint grinding noise - when the
CH timer is "ON". When the timer is "OFF" - no grinding noise from the
pump. When I say "grinding" the noise is very faint, not even as loud
as the familar "whoosh" and "whir" of an operational pump. This pump
is only 2 years old !!!

Now, I have been told you can take the pump bit off and leave the
plumbing bit in - by undoing the four Allen bolts attaching the
electric pump housing to the "rest".

How do I know it is the "electrical pump" that is the problem
rather than the "vanes" that are in line in the water flow?

The model is a Potterton Myson Celsia (I didn't note the exact
model)

I have searched and searched on the net for spares for this model
and can't find them anywhere.

If I buy the new pump , will it come with the "vanes" that sit in
the water flow. It is possible on this installation to isolate the
whole pump and replace it as the installer put an isolation valve both
above and below the pump.
However, I want to avoid removing the whole lot if at all possible


Thanks,

Clive

"Roger Mills" wrote in message
...

Sounds like a duff pump to me. If the pump is consuming electricity
but not
revolving it will get hot - from electrical energy dissipated in it.

If the pump is not pumping, little or no water will circulate. The
pipes may
get slightly warm due to conduction and natural convection.

If the water heated by the boiler cannot go anywhere, the boiler
will either
stop firing when its stat opens (if you're lucky) or will more likely
overheat so that its safety cutout trips. Does the boiler still fire?

If I am right, replacing the pump and, if necessary, re-setting the
overheat
trip on the boiler should fix your problem.

Roger

Its very common at this time of year for pumps to be found locked by crud
due to not being used over the summer.
Have you tried freeing the pump by turning the shaft with a screwdriver?
There is usualy a cover in the middle of the round end that you take off
with a coin to get to the screwdriver slot.

If the pump is u/s its standard practice to change the whole pump. That why
the isolating valves are there.
The shed all have pumps, get one with the same or higher head rating.
Virtually all replacement pumps should fit but trying to get bits of a new
pump to fit into old pump body would be fun to watch :-)