I have a Worcester 350 combi-boiler with a repeatable problem that the
service guy can't seem to fix! After about 2-3hrs of being on, the central
heating cycle of the boiler stops and the pipes go cool. The pump still
pumps the water round, but it's not firing up to heat it. Have replaced the
temperature sensor and a variety of other things.

I found I could temporarily resolve it: power the boiler off and on, or
press the reset-buttons (day and min) on the front panel to reset the clock
to 12:00am (if it got scrambled this is what it says to do). This pretty
much always works. For another 2 hours.

What do I need to replace to fix this?

Mike

On Sat, 02 Apr 2005 16:00:18 +0000, Mike Doyle wrote:

I have a Worcester 350 combi-boiler with a repeatable problem that the
service guy can't seem to fix! After about 2-3hrs of being on, the central
heating cycle of the boiler stops and the pipes go cool. The pump still
pumps the water round, but it's not firing up to heat it. Have replaced the
temperature sensor and a variety of other things.

I found I could temporarily resolve it: power the boiler off and on, or
press the reset-buttons (day and min) on the front panel to reset the clock
to 12:00am (if it got scrambled this is what it says to do). This pretty
much always works. For another 2 hours.

What do I need to replace to fix this?

In the face of things it sounds as if the clock/programmer unit is
giving trouble. Given that the only thing you do is to reset the clock and
the HW works fine (implied in your post) then replacing the clock should
work.

It might also be possible to by pass the clock and use some sort of
external programmable thermostat.








--
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

In message .uk, Ed
Sirett writes
On Sat, 02 Apr 2005 16:00:18 +0000, Mike Doyle wrote:

I have a Worcester 350 combi-boiler with a repeatable problem that the
service guy can't seem to fix! After about 2-3hrs of being on, the central
heating cycle of the boiler stops and the pipes go cool. The pump still
pumps the water round, but it's not firing up to heat it. Have replaced the
temperature sensor and a variety of other things.

I found I could temporarily resolve it: power the boiler off and on, or
press the reset-buttons (day and min) on the front panel to reset the clock
to 12:00am (if it got scrambled this is what it says to do). This pretty
much always works. For another 2 hours.

What do I need to replace to fix this?

In the face of things it sounds as if the clock/programmer unit is
giving trouble. Given that the only thing you do is to reset the clock and
the HW works fine (implied in your post) then replacing the clock should
work.

It might also be possible to by pass the clock and use some sort of
external programmable thermostat.

The OP isn't, by any chance, pressing the"Extra (2(?)) hour" button or
"Advance" button by mistake is he ?

--
geoff

"raden" wrote in message
...
In message .uk, Ed
Sirett writes
On Sat, 02 Apr 2005 16:00:18 +0000, Mike Doyle wrote:

I have a Worcester 350 combi-boiler with a repeatable problem that the
service guy can't seem to fix! After about 2-3hrs of being on, the
central
heating cycle of the boiler stops and the pipes go cool. The pump still
pumps the water round, but it's not firing up to heat it. Have replaced
the
temperature sensor and a variety of other things.

I found I could temporarily resolve it: power the boiler off and on, or
press the reset-buttons (day and min) on the front panel to reset the
clock
to 12:00am (if it got scrambled this is what it says to do). This
pretty
much always works. For another 2 hours.

What do I need to replace to fix this?

In the face of things it sounds as if the clock/programmer unit is
giving trouble. Given that the only thing you do is to reset the clock and
the HW works fine (implied in your post) then replacing the clock should
work.

Not sure I understand. The clock is working OK (it starts/stops CH
correctly), I just use the "reset" operation to fix the CH problem. Turning
complete power off and on to whole unit also causes same effect. The
problem is, after a while (2-3h) the pump continues to circulate the water
but it goes cool. The clock is not turning the unit off prematurely. It
seems the burn/no-burn cycle of the combustion chamber does not kick in. I
though it might be the temp sensor (thinking the water was at the correct
temp and thus stopping the heating until it went X degress lower), but that
has been replaced, and ... anyway... that would not be affected by a power
cycle, would it?

It might also be possible to by pass the clock and use some sort of
external programmable thermostat.

The OP isn't, by any chance, pressing the"Extra (2(?)) hour" button or
"Advance" button by mistake is he ?

No, not in this case. As explained, the pump and unit are operational, just
no heating of water circulating in the pipes any more :-(

Thanks for your quick responses. I had considered replacing one of the
sequencer cards. But I'd like to know why an electrical reset temporarily
fixes it before shelling out about £130 on that!

Mike

In message , Mike Doyle
writes

Thanks for your quick responses. I had considered replacing one of the
sequencer cards. But I'd like to know why an electrical reset temporarily
fixes it before shelling out about £130 on that!

I can't think of what, on either of the boards (yes I know one of them
is two boards piggybacked) would cause the electronics to latch (and if
anybody should, I suppose it's me)

However, I can't think of anything else.

I do have a Zagas 125 in stock, and I can prolly have a Zagas 126 board
ready in a couple of days

--
geoff