Are you able to follow the heat around, when the boiler is running for the 30 seconds - is it definitely going into the heating?
hot water outlet to ch just got warm
What about the return?
return cold not enough time to go round ch system
the return not enough time to go round ch system
If there was a circulation problem, or a problem with the pump it may heat the flow return the same amount
Rather than pumping around the system
i removed pump impeller & pump ok. diverter valve stripped cleaned &re assembled wax capsule placed in hot water&opened ok.d h w valve ok.micro switch ok.all stats & frost protectors ok.gas pressure tested&right press.both solenoids on gas valve tested & ok.[d h w system working ok +reaching right temp.] [when c h switched on boiler fires up for 5 secs. then shuts off. pump stays running] [then switched on c h again & operated micro switch on d h w held on for 2 mins. then boiler kept running on c h mode heated all rads ok turned room stat. up to max & boiler cut out on boiler stat when boiler stat. cooled boiler fired up again ran ok for rest of night. [it will not fire up again from cold start. sorry for the delay but i have been really unwell charlie.
Ok, so you have a problem firing from cold.
When running from cold and the boiler fires do the flow and return get warm - one, both?
one only felt warm at outlet behind diverter valve return pipe cold.
ok, so we are getting circulation while it is actually running
it sounds like the ch thermistor is shutting it down as you are not getting a fault light, but strange that it works normally once you have got it going
Once it has fired but cuts out, is there anything that shuts down before you lose heat? The divertor valve?
yes when i held micro sw on manually for two mins the ch system worked ok even firing up again after thermostat cutout and heated all rads in the normal amount of time [with ch on and running ok switched on hot water tap hot water ok turned off d h w tap for boiler to go back to c h just fired up for 5 secs then shut down
Does the pin not extend and push the microswitch?
i already said d h w valve works ok on demand for hot water [have already stripped d h w valve diapram ok pin to operate micro sw ok] hot water tap on pin pushes out ok & operates micro sw
i fitted a new thermistor i tought i was getting wrong resisance reading on my ohm meter fitted new thermistor fault same
Does your model not have one for the heating that pushes out when the pump runs?
Let me dig out a diagram - do you have the GC no.?
g c no 47 590 10
it only has one sw
Yes, you have the old one - there is a functional flow diagram on page 42 of this book;
and mentions the LED on the modulation pcb being on or off - off for ch demand, can you check this?
Let me know what you find