The Boiler is some 10 years old, and has developed a intermittent fault
...

Functions normally most of the time, then started to fail to supply
hot water for heating system.....This seems to happen if its been on
for a long period of time .. ie over night with the house stat turned
down (normal would be shut down 1200 till 0730)

When heating has failed -over night- Symptom's are :-

House thermostat demanding heat ,
(Radiators fully cold)
circulation pump running,
Boiler 'gas' fan running
No flame
No green light
No orange light.

This situation will remain so indefinitely

Found to cure problem.

Turning on house hot water tap

Fan remains running
Can here light 'click' from control box (relay operating)
Can hear (primary water circuit) diverter valve operate
Ignition system fires
Gas valve activates
Boiler lights
Green lamp lights
Orange lights

Hot water will run until tap closed .. normal operation .

Close hot tap
Diverter valve operates (can hear)
Boiler remains lit / re-lights
flame height rises to full then backs off - normal-
Heating functions normally

Till at some point the house thermostat shuts boiler down, then
randomly the heating fails.to re-start when demanded by thermostat.

I have changed the micro-switch on the hot water demand 'detector'
this at first seemed to of cleared the problem .. however this morning
... heating had failed .. open hot tap and close .. heating operated as
normal and has remained on all day ..

I don't have a circuit for the flame control module, I only have the
user documentation that came with the appliance..The schematic, only
shows the inter connections. I can only assume its the part that the
water demand sensor feeds that's developed the fault .. may be a
'dry joint' on the board as its seems only to happen after long
periods of use ?.... as the hot water function is 100 p/c reliable all
of the main parts of the boiler are functioning normally .. its got be
a electronic fail ..has anyone got the circuit ?

Sorry for the long post .. but that about describes the problem
Any one seen this problem ?

Tnx - Graham.

In message .com,
Graham writes
The Boiler is some 10 years old, and has developed a intermittent fault
..

Functions normally most of the time, then started to fail to supply
hot water for heating system.....This seems to happen if its been on
for a long period of time .. ie over night with the house stat turned
down (normal would be shut down 1200 till 0730)

When heating has failed -over night- Symptom's are :-

House thermostat demanding heat ,
(Radiators fully cold)
circulation pump running,
Boiler 'gas' fan running
No flame
No green light
No orange light.

This situation will remain so indefinitely

Found to cure problem.

Turning on house hot water tap

Fan remains running
Can here light 'click' from control box (relay operating)
Can hear (primary water circuit) diverter valve operate
Ignition system fires
Gas valve activates
Boiler lights
Green lamp lights
Orange lights

Hot water will run until tap closed .. normal operation .

Close hot tap
Diverter valve operates (can hear)

But is it actually moving far enough to operate the microswitches

Boiler remains lit / re-lights
flame height rises to full then backs off - normal-
Heating functions normally

Till at some point the house thermostat shuts boiler down, then
randomly the heating fails.to re-start when demanded by thermostat.

I have changed the micro-switch on the hot water demand 'detector'
this at first seemed to of cleared the problem .. however this morning
.. heating had failed .. open hot tap and close .. heating operated as
normal and has remained on all day ..

I don't have a circuit for the flame control module,

Why should it be the flame sup cct ? - I thought it worked in CH mode

It could be the thermostatic ctrl board

I only have the
user documentation that came with the appliance..The schematic, only
shows the inter connections. I can only assume its the part that the
water demand sensor feeds that's developed the fault .. may be a
'dry joint' on the board as its seems only to happen after long
periods of use ?.... as the hot water function is 100 p/c reliable all
of the main parts of the boiler are functioning normally .. its got be
a electronic fail ..has anyone got the circuit ?

Sorry for the long post .. but that about describes the problem
Any one seen this problem ?

Tnx - Graham.


--
geoff

Ok well i checked the micro switch opreation .. and it functions fine
with low/medium hot water flow ..hot water supply is fine - 100 p/c ...

flame control module, well i mean the cct for the whole control box -
there are a few boards in there ..

it must be something that the direct hot water over-rides as once you
have run the hot water .. dam thing works fine again ..

also a slight tap on the box has the same affect .heating come back on
.. hence i think its a joint on one of the boards ... but which one ..

when it clears .. you can here the relay 'click' in the control box
prior to the gas opeing .. so what drives the relay ?

Tnx - G .

In message .com,
Graham writes
Ok well i checked the micro switch opreation .. and it functions fine
with low/medium hot water flow ..hot water supply is fine - 100 p/c ...

flame control module, well i mean the cct for the whole control box -
there are a few boards in there ..

it must be something that the direct hot water over-rides as once you
have run the hot water .. dam thing works fine again ..

also a slight tap on the box has the same affect .heating come back on
. hence i think its a joint on one of the boards ... but which one ..

when it clears .. you can here the relay 'click' in the control box
prior to the gas opeing .. so what drives the relay ?

Top board - fl sup board
bottom board - fan ctrl board

neither are interested in what mode it's in

it's either the motherboard or the thermostatic board - the middle one
.... if that is indeed the problem

--
geoff

On Sun, 12 Mar 2006 09:02:25 -0800, Graham wrote:

The Boiler is some 10 years old, and has developed a intermittent fault
..

Functions normally most of the time, then started to fail to supply
hot water for heating system.....This seems to happen if its been on
for a long period of time .. ie over night with the house stat turned
down (normal would be shut down 1200 till 0730)

When heating has failed -over night- Symptom's are :-

House thermostat demanding heat ,
(Radiators fully cold)
circulation pump running,
Boiler 'gas' fan running
No flame
No green light
No orange light.

This situation will remain so indefinitely

Found to cure problem.

Turning on house hot water tap

Fan remains running
Can here light 'click' from control box (relay operating)
Can hear (primary water circuit) diverter valve operate
Ignition system fires
Gas valve activates
Boiler lights
Green lamp lights
Orange lights

Hot water will run until tap closed .. normal operation .

Close hot tap
Diverter valve operates (can hear)
Boiler remains lit / re-lights
flame height rises to full then backs off - normal-
Heating functions normally

Till at some point the house thermostat shuts boiler down, then
randomly the heating fails.to re-start when demanded by thermostat.

I have changed the micro-switch on the hot water demand 'detector'
this at first seemed to of cleared the problem .. however this morning
.. heating had failed .. open hot tap and close .. heating operated as
normal and has remained on all day ..

I don't have a circuit for the flame control module, I only have the
user documentation that came with the appliance..The schematic, only
shows the inter connections. I can only assume its the part that the
water demand sensor feeds that's developed the fault .. may be a
'dry joint' on the board as its seems only to happen after long
periods of use ?.... as the hot water function is 100 p/c reliable all
of the main parts of the boiler are functioning normally .. its got be
a electronic fail ..has anyone got the circuit ?

Sorry for the long post .. but that about describes the problem
Any one seen this problem ?

This seems like it's the diverter valve or the servo valve or
diverter valve micro switches. When the CH demand is applied the pump
moves the diverter valve from neutral to the left to going to CH mode.
When the diverter valve arrives at the full left position one or two micro
switches are made to initiate ignition.

IME a good many of the problems with the boiler (which is a generally very
reliable unit) are with the water flow detector and/or servo valve
assembly. This is the gadget at the low front middle on the boiler.

The piston from the water flow diaphragm get sticky at the beginning or
end of its travel. as it works the servo valve and DHW microswitch.
However YMMV.

This problem is marginal/intermittent and exercising the valve gear by
turning on a tap temporarily clears the problem.

--
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

In message .uk, Ed
Sirett writes
On Sun, 12 Mar 2006 09:02:25 -0800, Graham wrote:

I don't have a circuit for the flame control module, I only have the
user documentation that came with the appliance..The schematic, only
shows the inter connections. I can only assume its the part that the
water demand sensor feeds that's developed the fault .. may be a
'dry joint' on the board as its seems only to happen after long
periods of use ?.... as the hot water function is 100 p/c reliable all
of the main parts of the boiler are functioning normally .. its got be
a electronic fail ..has anyone got the circuit ?

Sorry for the long post .. but that about describes the problem
Any one seen this problem ?

This seems like it's the diverter valve or the servo valve or
diverter valve micro switches.

That's what I said in the first place

--
geoff

......, this mean ive changed the wrong micro switch ... ? the one i
suspected was on the back of the hot water flow sensor .. for want of a
better cescription ..ther is only 1 microw switch on this item driven
by a rotating cam, that has a return spring ..


are the other 2 switches on the valve assembly directly over that one
... ? seem to be locked with locking wire ..

Tnx

G.

Just had a look at the boiler .. can the swiches be changed on that
unit .. looks like a sealed assembly .. need to change the whole thing
?

Tnx for your help

Graham .

In message .com,
Graham writes
....., this mean ive changed the wrong micro switch ... ? the one i
suspected was on the back of the hot water flow sensor .. for want of a
better cescription ..ther is only 1 microw switch on this item driven
by a rotating cam, that has a return spring ..


are the other 2 switches on the valve assembly directly over that one
.. ? seem to be locked with locking wire ..

The diverter valve has two microswitches on top - as the shaft moves up,
one changes from NC to NO, the other from NO to NC

You need to make sure that the they're changing over properly

--
geoff

where is this located in the boiler ... i dont think im looking a the
right assembly .. the only thing i can see .. looks sealed to me .. may
be gas valve directly over the hot water sensor ?

G ..