On Sun, 23 Nov 2008 12:34:33 +0000, newshound wrote:

When you run the DHW with the CH off, does the boiler seem to get noisier
before it cuts out? This is the symptom with mine (no pilot light, and it
cuts out sooner than 5 minutes), but it is cutting out on primary water
over-temperature (hence sounds of incipient boiling) because not enough heat
is getting transferred to the DHW through the partially blocked heat
exchanger. Are you in a hard water area? In my experience, 12 years is a
pretty good life for a modern combi.

Good point. When you have to relight the boiler is there a reset button
somewhere you have to press back in before it will relight? Does the
thermocouple have either a couple of tags partway along its length, or
where it's connected to the gas valve are there a couple of wires going
off to an overheat trip switch?

If you can feel the flow pipe from the heat exchanger (inside the boiler,
not the one coming out of the boiler to the CH - and take care you don't
touch anything electrical while doing this) does it get much hotter on DHW
than on CH? (An infra-red thermometer or some sort of thermometer you can
get onto this pipe would tell you more accurately).

--
John Stumbles -- http://yaph.co.uk

Seagull Management
Management technique characterised by flying in, making a lot of noise,
crapping on everything, and then leaving.