I have a Potterton Profile 50e boiler, and lately the (thermal?)
cut-out has started tripping. This results in the pump going
continuously, but no hot water.
It happily resets manually, and starts up again.
It seems to trip 4/5 times a week, at different times/conditions - no
obvious pattern.

Any ideas?

Obviously I am not going to take the boiler apart (unqualified), but
if the cause is elsewhere in the system, I beleive I could fix it.

Neal

In an earlier contribution to this discussion,
Neal Harwood wrote:

I have a Potterton Profile 50e boiler, and lately the (thermal?)
cut-out has started tripping. This results in the pump going
continuously, but no hot water.
It happily resets manually, and starts up again.
It seems to trip 4/5 times a week, at different times/conditions - no
obvious pattern.

Any ideas?

Obviously I am not going to take the boiler apart (unqualified), but
if the cause is elsewhere in the system, I beleive I could fix it.

Neal

This normally happens when the boiler and pump are turned off by a room
stat - and the residual heat in the boiler's heat exchanger continues to
heat the water to the point where the overheat stat trips.

Boilers which are susceptible to this usually control the pump directly -
and have an over-run stat which continues to run the pump for a while after
the boiler stops firing - in order to dissipate the residual heat.

Clearly, the water must have an available circulation path during this
over-run period - often requiring a by-pass loop, depending on the exact
setup.

The first thing to check is whether your boiler has a pump over-run stat
and, if so, to make sure that it is wired up correctly.

If you still have problems, come back with further details of your system
setup. Does it look like one of the "plans" described in
http://content.honeywell.com/uk/homes/systems.htm ?

--
Cheers,
Set Square
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In message , Neal
Harwood writes
I have a Potterton Profile 50e boiler, and lately the (thermal?)
cut-out has started tripping. This results in the pump going
continuously, but no hot water.
It happily resets manually, and starts up again.
It seems to trip 4/5 times a week, at different times/conditions - no
obvious pattern.

Any ideas?

The impeller of the pump hasn't broken off the shaft has it ?

--
geoff

In article ,
raden writes:
In message , Neal
Harwood writes
I have a Potterton Profile 50e boiler, and lately the (thermal?)
cut-out has started tripping. This results in the pump going
continuously, but no hot water.
It happily resets manually, and starts up again.
It seems to trip 4/5 times a week, at different times/conditions - no
obvious pattern.

Any ideas?

The impeller of the pump hasn't broken off the shaft has it ?

or as happened to a friend of mine, the blades had all fallen
off the impeller (and were nowhere to be found).

--
Andrew Gabriel

In an earlier contribution to this discussion,
raden wrote:

In message , Neal
Harwood writes
I have a Potterton Profile 50e boiler, and lately the (thermal?)
cut-out has started tripping. This results in the pump going
continuously, but no hot water.
It happily resets manually, and starts up again.
It seems to trip 4/5 times a week, at different times/conditions - no
obvious pattern.

Any ideas?

The impeller of the pump hasn't broken off the shaft has it ?

I don't think the system would run for between 1/5 and 1/4 of a week if it
had!

I think it's something to do with sets of circumstances which occur now and
again where the pump can't effectively overrun. Maybe it's not wired to do
so, or maybe there isn't a by-pass and it gets caught out when all the TRVs
are shut.
--
Cheers,
Set Square
______
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In message , Set Square
writes
In an earlier contribution to this discussion,
raden wrote:

In message , Neal
Harwood writes
I have a Potterton Profile 50e boiler, and lately the (thermal?)
cut-out has started tripping. This results in the pump going
continuously, but no hot water.
It happily resets manually, and starts up again.
It seems to trip 4/5 times a week, at different times/conditions - no
obvious pattern.

Any ideas?

The impeller of the pump hasn't broken off the shaft has it ?

I don't think the system would run for between 1/5 and 1/4 of a week if it
had!

You have a point there - I'll try to read threads better in future
--
geoff

raden wrote in message ...
In message , Set Square
writes
In an earlier contribution to this discussion,
raden wrote:

In message , Neal
Harwood writes
I have a Potterton Profile 50e boiler, and lately the (thermal?)
cut-out has started tripping. This results in the pump going
continuously, but no hot water.
It happily resets manually, and starts up again.
It seems to trip 4/5 times a week, at different times/conditions - no
obvious pattern.

Any ideas?

The impeller of the pump hasn't broken off the shaft has it ?

I don't think the system would run for between 1/5 and 1/4 of a week if it
had!

You have a point there - I'll try to read threads better in future



Thanks for the replies so far
I believe the pump is fine, because it DOES work most of the time,
just cuts out occasionally.
It has also only started doing this recently. It used to happen VERY
occasionally (2 times per year), but recently it is much more
frequent.

This 'cut-out due to residual heat' sounds very feasible
I will try and work out the circuit type (thanks for the link) and get
back to you

Neal

"Set Square" wrote in message ...
In an earlier contribution to this discussion,
Neal Harwood wrote:

I have a Potterton Profile 50e boiler, and lately the (thermal?)
cut-out has started tripping. This results in the pump going
continuously, but no hot water.
It happily resets manually, and starts up again.
It seems to trip 4/5 times a week, at different times/conditions - no
obvious pattern.

Any ideas?

Obviously I am not going to take the boiler apart (unqualified), but
if the cause is elsewhere in the system, I beleive I could fix it.

Neal

This normally happens when the boiler and pump are turned off by a room
stat - and the residual heat in the boiler's heat exchanger continues to
heat the water to the point where the overheat stat trips.

Boilers which are susceptible to this usually control the pump directly -
and have an over-run stat which continues to run the pump for a while after
the boiler stops firing - in order to dissipate the residual heat.

Clearly, the water must have an available circulation path during this
over-run period - often requiring a by-pass loop, depending on the exact
setup.

The first thing to check is whether your boiler has a pump over-run stat
and, if so, to make sure that it is wired up correctly.

If you still have problems, come back with further details of your system
setup. Does it look like one of the "plans" described in
http://content.honeywell.com/uk/homes/systems.htm ?

Having just read some old (c1998) posts (I Love GOOGLE Groups),
someone else suggested problems with an airlock in the CH system
We HAVE had to drain the system a couple of times over the last year
(to move some pipes and rads in the basement).
Is it possible I have an airlock of some sort? Where would it be?
Would it cause my symptoms? And of course, HOW do I get rid of it?

In an earlier contribution to this discussion,
Neal Harwood wrote:


Having just read some old (c1998) posts (I Love GOOGLE Groups),
someone else suggested problems with an airlock in the CH system
We HAVE had to drain the system a couple of times over the last year
(to move some pipes and rads in the basement).
Is it possible I have an airlock of some sort? Where would it be?
Would it cause my symptoms? And of course, HOW do I get rid of it?

I doubt if it's that. An air lock after re-filling can prevent any primary
circlation (I've had one!) but once you've got circulation going, any
residual air will usually park itself somewhere where it doesn't do any
major harm - probably in one of the radiators. I don't think an air lock is
likely to cause an intermittent circulation failure.

Of course, I could be wrong . . .
--
Cheers,
Set Square
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