Hi

I've got an intermittent fault with a 5 year old combi boiler. Every
3-4 months or so the heating will pack up for a couple of days and then
sort itself out.

What happens is that combi seems to stop responding to the water system
by not delivering hot water through the central heating. The hot
water taps work fine, the boiler fires up just as normal. But as far
as the central heating goes, the boiler fires up every 10 minutes or so
(perhaps less frequently), gives about 20 seconds of clicking and
whirring (as usual) and then switches off. The obvious effect is that
the radiators therefore don't get hot!!

The problem is that each time this happens, we give it 24 hours or so,
then despair (and freeze), call a plumber and by the time they turn up
(or schedule to turn up) the heating sorts itself out.

Any DIY suggestions for what I could do to investigate? I know the
boiler itself is out of bounds, but do you think draining the system /
cleaning the water in the radiators might help? Perhaps its a blockage
in the system somewhere which means that there aren't enough pressure
changes in the system to prompt the combi into action? I don't know
much about this stuff, so any pointers gratefully received, either to
do myself or to get a plumber in to at least try something
constructive!

Thanks!

Matt

On 14 Dec 2006 13:54:43 -0800 wrote :
I've got an intermittent fault with a 5 year old combi boiler.
Every
3-4 months or so the heating will pack up for a couple of days
and then sort itself out.

You'll increase the chance of a helpful answer if you tell us the
make and model

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk

On Dec 14, 11:06 pm, Tony Bryer wrote:
On 14 Dec 2006 13:54:43 -0800 wrote :

I've got an intermittent fault with a 5 year old combi boiler.
Every
3-4 months or so the heating will pack up for a couple of days
and then sort itself out.You'll increase the chance of a helpful answer if you tell us the
make and model

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk

OK, will do when I get home - but my assumption is that it is something
"fundamental", rather than boiler specific. In fact, it may be
completely unrelated to the boiler itself (as it produces hot water
fine).

My gut feeling is that it is something to do with the circulation
system itself (by which I mean the water flowing around the pipes,
radiators and radiator thermostats) rather than the boiler which is
causing the problem; and therefore any useful suggestions around that
side of things would be useful.

One thing I should note; the top radiator in the house (in the
converted attic) does seem to get a lot of air in it, to the extent
that when I vented it the other day I had to re-prime the system with
more water before it would force all of the air out of the system. But
we don't seem to have any water leaks, so I don't see how air would be
getting into the system.

I'll post the boiler details later on today, but thanks for reading and
responding Tony.

Matt

On Fri, 15 Dec 2006 01:56:07 -0800, matthew.larkin wrote:

On Dec 14, 11:06 pm, Tony Bryer wrote:
On 14 Dec 2006 13:54:43 -0800 wrote :

I've got an intermittent fault with a 5 year old combi boiler.
Every
3-4 months or so the heating will pack up for a couple of days
and then sort itself out.You'll increase the chance of a helpful answer if you tell us the
make and model

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk

OK, will do when I get home - but my assumption is that it is something
"fundamental", rather than boiler specific. In fact, it may be
completely unrelated to the boiler itself (as it produces hot water
fine).

My gut feeling is that it is something to do with the circulation
system itself (by which I mean the water flowing around the pipes,
radiators and radiator thermostats) rather than the boiler which is
causing the problem; and therefore any useful suggestions around that
side of things would be useful.

One thing I should note; the top radiator in the house (in the
converted attic) does seem to get a lot of air in it, to the extent
that when I vented it the other day I had to re-prime the system with
more water before it would force all of the air out of the system. But
we don't seem to have any water leaks, so I don't see how air would be
getting into the system.

I'll post the boiler details later on today, but thanks for reading and
responding Tony.

Matt

It's almost certainly the diverter valve inside the combi.
Make,model and date of installation would be useful.




--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Ed Sirett wrote:
On Fri, 15 Dec 2006 01:56:07 -0800, matthew.larkin wrote:

On Dec 14, 11:06 pm, Tony Bryer wrote:
On 14 Dec 2006 13:54:43 -0800 wrote :
and then sort itself out.You'll increase the chance of a helpful answer if you tell us the
make and model

OK, will do when I get home - but my assumption is that it is something
"fundamental", rather than boiler specific. In fact, it may be
completely unrelated to the boiler itself (as it produces hot water
fine).

[Snipped]

I'll post the boiler details later on today, but thanks for reading and
responding Tony.

Matt

It's almost certainly the diverter valve inside the combi.
Make,model and date of installation would be useful.


Its a Potterton Combi 100 - installed approx 6 years ago I believe.

Cheers!

Matt

On Fri, 15 Dec 2006 12:54:58 -0800, matthew.larkin wrote:

Ed Sirett wrote:
On Fri, 15 Dec 2006 01:56:07 -0800, matthew.larkin wrote:

On Dec 14, 11:06 pm, Tony Bryer wrote:
On 14 Dec 2006 13:54:43 -0800 wrote :
and then sort itself out.You'll increase the chance of a helpful answer if you tell us the
make and model

OK, will do when I get home - but my assumption is that it is something
"fundamental", rather than boiler specific. In fact, it may be
completely unrelated to the boiler itself (as it produces hot water
fine).

[Snipped]

I'll post the boiler details later on today, but thanks for reading and
responding Tony.

Matt

It's almost certainly the diverter valve inside the combi.
Make,model and date of installation would be useful.


Its a Potterton Combi 100 - installed approx 6 years ago I believe.


I think that model has a conventional water flow diaphragm and diverter
valve unit. I'm surprised that it is an intermittent fault though.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Ed Sirett wrote:
It's almost certainly the diverter valve inside the combi.
Make,model and date of installation would be useful.


Its a Potterton Combi 100 - installed approx 6 years ago I believe.


I think that model has a conventional water flow diaphragm and diverter
valve unit. I'm surprised that it is an intermittent fault though.

Its literally 4 times in the last 2 years (since we've been in the
house) for a max of 2 days at a time (3 of those times have been on a
Friday evening, conveniently (not) enough!!).

The water from the rad's is fairly grimy when I've vented them, so its
certainly not the cleanest system in the world. I'm sure some TLC
wouldn't go amiss. The radiators are a mix of old and new too.

Anyway, got a recommended plumber coming round next week. Shame it
will all be working fine by then though!!

Matt

On Sun, 17 Dec 2006 12:57:16 -0800, matthew.larkin wrote:

Ed Sirett wrote:
It's almost certainly the diverter valve inside the combi.
Make,model and date of installation would be useful.


Its a Potterton Combi 100 - installed approx 6 years ago I believe.


I think that model has a conventional water flow diaphragm and diverter
valve unit. I'm surprised that it is an intermittent fault though.

Its literally 4 times in the last 2 years (since we've been in the
house) for a max of 2 days at a time (3 of those times have been on a
Friday evening, conveniently (not) enough!!).

The water from the rad's is fairly grimy when I've vented them, so its
certainly not the cleanest system in the world. I'm sure some TLC
wouldn't go amiss. The radiators are a mix of old and new too.

Anyway, got a recommended plumber coming round next week. Shame it
will all be working fine by then though!!

Matt

Could well be debris in the primary circuit.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards