vaillant thermocompact

[lor]

the manual says no bypass required (inbuilt) .someone has fitted it to an s plan ( 3 x 2 port vlvs )with no bypass and boiler overheating so no the hex o ring seal leaks.
whats your experience of this model ?

 

[chrishutt]

so no the hex o ring seal leaks

What's this supposed to mean?

Also is the boiler internal by-pass working when required?

How do you know the boiler is overheating?

 

[lor]

so now the heat exchanger o ring seals have started to leak.
i can feel the autobypass pipe is hot
boiler is hissing (ive fitted a new pump)
thanks alot chris

 

[chrishutt]

Have you checked that the burner shuts off (but the pump continues) when the motorised valves shut?

Doesn't the overheat stat operate and require manual resetting?

Which model of thermocompact is it - the VC series?

Is the new pump speed adjustable? Is it on highest setting?

 

[lor]

pump grundfos speed 3

blr approx 4-5 years old

no programmmer so when zone valves shut boiler is still firing,can the auto bypass cope ?

no it is not locking out ,or giving a warning message

data badges call it 624e

 

[chrishutt]

no programmmer so when zone valves shut boiler is still firing,

This is clearly the root of the problem. The control wiring is wrong. The boiler should only receive a call for heat when at least one motorised valve is open. You need to get a heating engineer in to inspect and rectify the wiring.

 

[ACOperson]

Shouldn't the boiler seals be able to cope with this higher system pressure? Maybe the answer is just to buy an o-ring pack from your merchant and try replacing the seals.

Is the hissing kettling? If so maybe suspect a scaled heat exhanger which could be retaining too much heat after the burner has gone off.