Ideal Classic FF

[tripletop]

After removing and re-fitting two downstairs radiators the boiler will light up and run for about 5 minutes, then the gas light goes out but the fan continues to run for a long time (over 15 minutes). The boiler can be switched off using the programer or room stat but will not re-light until some time has elapsed (temperature drops?) The resetable themo-cutout does not activate and the pump and three way valve seem to be working. There is water supply to the header tank.
Before calling a suitably qualified engineer can anyone suggest a probable cause?
Thanks,

 

[gaspro1981]

sounds like a circulation issue try venting all the rads and the cylinder primaries with the pump turned off

 

[kevplumb]

try venting the pump

 

[gaspro1981]

kev good shout

 

[kevplumb]

not when youve been caught out a few times

 

[tripletop]

What a fast response!
All rads have been bled and show water, including the refitted rads.
Is there a special method to bleed the pump? The pump spindle turns freely and the pipes either side are hot.
I see that another post had a similar problem traced to a siezed ball valve in the HE tank (?) could this be a possible cause?

 

[kevplumb]

not if its got water in

View media item 667

 

[tripletop]

Ah, I see what you mean.
Had this access screw off to turn the pump spindle and plenty of water came out - would this have been sufficient to bleed the pump?

 

[kevplumb]

yeah

thats that idea shot

are the zone valves opening

is there a vent point on the cylinder View media item 457

 

[tripletop]

Hi Kev,
If you mean the three way valve, then that seems to work. All the stopcock valves are open.
The boiler will fire up and run for a few minute, sufficient to warm the rads, the cold boiler return just starts to get lukewarm before the boiler then goes out but the fan continues to run. (interesting neon orange glow from behind the contrrol facia!) It will stop if the room thermostat setting is reduced below ambient, starting again if the stat is turned up again.
The cylinder does not appear to have a separate vent.
Thanks for your help so far![/img]

 

[gaspro1981]

the orange neon will only illuminate when there is a demand from either hotwater or htg
this still sounds like a circulation problem to me how does the system sound can you hear any air rushing around the radiators or the vicinity of the airing cupboard

 

[tripletop]

No, just the pump and slight water circulating noise.

 

[mickyg]

try draining some water from the system and checking that the header tank level drops and refills. Its possible you may have a blockage

 

[kevplumb]

when the boiler goes out is the pump still running

 

[tripletop]

The pump continues to run when the boiler goes out, the boiler fan also runs (sorry to keep harping on about that). They both continue to run indefinately or until the room stat is manually tripped or the programmer is swithched off. The pump body is warm/ hot and the pipes are cold. There seems to be plenty of water in the system.