Vaillant TurboMAX Boiler - Pressure Issue - Looking for Advice

[Bubble Moose]

Hi everyone,

I’m having some trouble with my Vaillant TurboMAX boiler and could really use some advice. Here are the symptoms:

The boiler pressure sits at 1.5 bar when idle.

As soon as the boiler fires up, the pressure rapidly increases to 3 bar, triggering the safety system and shutting the boiler down.

Once the boiler shuts off, the pressure slowly drops back to 1.5 bar.

Over time (even when the boiler isn’t running), the system pressure seems to creep up by itself.


I’ve also noticed that when the boiler was working, the pressure used to increase over time, which seems unusual.

From what I’ve read, this could point to an issue with the expansion vessel, pressure relief valve, or potentially a faulty heat exchanger. I’m leaning toward the heat exchanger because of the gradual pressure increase over time, but I’d love to hear your thoughts before I go any further.

Has anyone dealt with similar symptoms, and if so, what was the fix? Any advice would be greatly appreciated!

Video below.

Thanks in advance!

 

[cross thread]

Have the expa vessel recharged first,the filling loop maybe passing so have that checked as well

 

[Stuckinarut]

As above, expansion issue. How come you ran it in P.1? Temp was 128 there!

 

[Bubble Moose]

Ran at p1 to get it to fire for the video.

I have now replaced..
The expansion vessel.
Heat exchabge.
PCB.

Issue still is persisting.

This is a weird one