Background: Central Heating uses Potterton Suprima 80 ( 2 yr old) ;
Honeywell timer ( Stc6400)NEW:
All rads with stats + hot water tank separate thermo;
Wired to Y plan.
The fault:
Heating started to come on 2 or 3 hrs after timer programm, then failed
to ignite boiler.
Hot water will operate fine with or without the Heating switched on.

Heating now will operate only when Hot Water timer is also on,
otherwise boiler fails to light .

Advice sought is this aboiler or Electrical fault?

Any 1st steps to check?
Your help sought
Mike

In an earlier contribution to this discussion,
Mike wrote:

Background: Central Heating uses Potterton Suprima 80 ( 2 yr old) ;
Honeywell timer ( Stc6400)NEW:
All rads with stats + hot water tank separate thermo;
Wired to Y plan.
The fault:
Heating started to come on 2 or 3 hrs after timer programm, then
failed to ignite boiler.
Hot water will operate fine with or without the Heating switched on.

Heating now will operate only when Hot Water timer is also on,
otherwise boiler fails to light .

Advice sought is this aboiler or Electrical fault?

Any 1st steps to check?
Your help sought
Mike

I'd put my money on it being an almost failed motor in the actuator part of
the 3-port valve. If the motor *almost* works, it can take it a *very* long
time to move the valve from the HW to the CH position - and it has to be
most of the way there before it switches the boiler and pump on, unless
there is also a HW demand - in which case the boiler is switched directly,
and not via the actuator. Have a look at the Y-Plan wiring diagram in
http://content.honeywell.com/uk/homes/systems.htm and you'll hopefully see
what I mean.

It's *just* possible that the wet part of the valve has partially seized -
which could cause the same symptoms - but far more likely that it's the
actuator. With most makes of valve you can replace the actuator without
having to disturb the wet part. You can even replace just the motor if
you're happy with soldering.
--
Cheers,
Set Square
______
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Set Square wrote:

In an earlier contribution to this discussion,
Mike wrote:


Heating now will operate only when Hot Water timer is also on,
otherwise boiler fails to light .

Advice sought is this aboiler or Electrical fault?

Any 1st steps to check?
Your help sought
Mike

I'd put my money on it being an almost failed motor in the actuator part of
the 3-port valve. If the motor *almost* works, it can take it a *very* long
time to move the valve from the HW to the CH position - and it has to be
most of the way there before it switches the boiler and pump on, unless
there is also a HW demand - in which case the boiler is switched directly,
and not via the actuator. Have a look at the Y-Plan wiring diagram in
http://content.honeywell.com/uk/homes/systems.htm and you'll hopefully see
what I mean.

It's *just* possible that the wet part of the valve has partially seized -
which could cause the same symptoms - but far more likely that it's the
actuator. With most makes of valve you can replace the actuator without
having to disturb the wet part. You can even replace just the motor if
you're happy with soldering.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.
Please forgive my next Question: Where would the 3 way value be
located? close to the pump my guess ans yes happy to solder items. Many
thnaks for your advice Mike

In an earlier contribution to this discussion,
Mike wrote:

Please forgive my next Question: Where would the 3 way value be
located? close to the pump my guess ans yes happy to solder items.
Many thnaks for your advice Mike

Trace the flow pipe from the boiler to the hot water cylinder in the airing
cupboard. At some point there will be a pump. Somewhere *after* the pump the
HW and CH circuits separate. This is where the valve will be. It may well be
in the airing cupboard - but it might not be. It will look something like
http://tinyurl.com/chyuh - but it may not be blue.
--
Cheers,
Set Square
______
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Set Square wrote:


Trace the flow pipe from the boiler to the hot water cylinder in the airing
cupboard. At some point there will be a pump. Somewhere *after* the pump the
HW and CH circuits separate. This is where the valve will be. It may well be
in the airing cupboard - but it might not be. It will look something like
http://tinyurl.com/chyuh - but it may not be blue.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

Yes the wiring and 3 way valve are below a panel under the H water
tank, a replacement part sourced and fitted 25 mins later Bliss Heating
back on

Thanks again for all your help
Best Wishes to all on DIY
Mike