Solved - help needed, Saunier duval f24e therma classic - central heating not working - it was not the boiler

[Allanp34]

proud owner of a saunier duval f24e therma classic . That does not want to work with the central heating but the hot water is fine after it was refilled. [heating system was drained for decorating]

(advice for these boilers is to replace - and I could not agree more - but we have already moved and are selling the apartment on - the new owners can get grants here to upgrade to a more "modern" heating system )

The central heating flow pipe only gets warm a few cm's below the boiler. Never too hot to hold.

Could it have been messed up during the refilling - if the radiator return or flow valves were closed when the boiler was switched on?

The diverter valve replaced about 5yrs ago when the valve body split. Genuine parts - used.
Parts diag - https://www.sparesbase.co.uk/saunier-themaclassic-f24e-10000877-3549855/explodedviews

This is whats been done so far :
Diverter solenoid - certainly looks ok, changing positions when going from hotwater to central heating.
I think it defaults to hotwater, and extends the actuator when on central heating. But would need to check.

Diverter valve - can actuate this manually (bit tricky to do so for any length of time!!!)
And still no joy, the heating flow pipe remains cold (just the usual first few cm only get quite warm )

Changed the diverter valve cartridge - thankfully came with a diagram. So I did not have to worry about the extra part not being used - looks like a blanking cap? However this did not fix things.

When the system is pressurised and the solenoid removed, the brass pin of the diverter valve will gently extend outwards about a cm or more. Is that normal? It was like that with the old and the new cartridge. Easy to press back in, until the force of the spring is felt, then it is quite hard to press with fingers bent inside the boiler.

Checked the heating circuit filter - looked in good condition. Washed and re-installed.

Removed the bypass valve cleaned and re-installed - all looks ok.

At a bit of a loss what to do next.

Thanks - Allan.

 

[kidgreen61]

Sounds like pump seized/full of air

 

[Allanp34]

thanks for replying. Had the the front cap off the pump and the thing is spinning for sure with plenty of force.

How would I check for either of those things? And then what to do about them?

The pump air bleed valve does sound like it releases air when the system is refilled. But is it working well enough?

Any point of refilling the system but this time with the diverter valve on for central heating?

There is a lot more gurgling and surging of water than have know from the boiler before so there is definitely something different.

Cheers - A

 

[CountryFan]

Are all the valves open? Did you close any off under the boiler?

 

[Allanp34]

Will check and make sure I am not doing something stupid there. But pretty sure they are open as the cold water feed is the same valve on it and that works ok for filling the boiler and the hot water then flows. Even tried the heating valve at a 50 / 50 setting just in case - a tip from a friend.
Going to try a back feed this evening with the diverter valve depressed inwards which I think is the heating circuit engaged. Normally iy defaults ot hot water so it would have been filled when the hot water circuit was active. Hope is this would purge any air in there.

Cheers - A

 

[Allanp34]

Are all the valves open? Did you close any off under the boiler?

turns out you were correct - sort of. It made me check a few things and turns out all of the return valves on each radiator was closed. The rads had been removed for decorating 6 months or more back and this detail was forgotten.

With no other bypass valve out there, no return path for any of the hot water - bypass valve within the boiler was working overtime.

Thanks everyone for helping the process along. Embarrassed and very relieved.
Wasted enough on the diverter valve cartridge - but could have been a lot worse.

Much appreciate everyones input.