fuelsaver 40 50 cutting out

[allanmacuser]

We have a glow-worm 40 50 fuelsaver wall mounted l have bled the system and replaced the thermo coupler. Now the strange thing is when the boiler is running all the radiators its just fine. The problem we have have is that when we turn the valve off for the radiators and just want to heat the water the boiler cut out. There is a slight kettling noise and the pump seams to be working ok.

Any ideas
Regards
Allan stoke on trent

 

[ChrisR]

Short of water in system? Check f/e tank has water and that the feed is not blocked, by draining a bit of water and confirming refill of f/e.

Also check bleed point in pipe from boiler where top one goes into side of hw cylinder. ie next to the cylinder.

 

[allanmacuser]

thank you for your reply i will try that today

once more
thank you