Vaillant TurboMAX 837 losing pressure then Red Light

[bluebossa]

Hi there, Well winters here and the Central Boiler is not firing reliably.

I just drove home through the Snow from a family Christmas in Ormskirk and the house was freezing and the red light on the Boiler was on.

A quick press and it's up again - pressure is at Zero.
Quick tweak underneath and put a bit of water in - 1bar and it's off and the house is coming back to temperature.

Seems to be losing pressure every other day now - so action / repair needed.

Well, like most at this time of year, I'm broke and wondered if I can diagnose and fix so I've read a few posts on this forum - which seem to point to the PRV Pressure Relief Valve blowing off and or the Expansion tank not being pressurized.

The Boiler is circa 8 years old and has been working fine though this isn't a new this year problem.

None of the Radiators exhibit a leak - so where do I start and can I diagnose and fix it myself or is it a Valliant Engineer job?

Thanks in advance..

 

[ALCPlumbing]

Obviously as you said you need to check the pressure relief pipe to see if it's dripping. If it is expansion vessel issues which is most likely you will see the pressure rise significantly when the central heating gets up to temperature.
You may find it's dripping all the time from the PRV as sometimes they don't seal again properly so the pressure rise when hot is the best indication.
If you're lucky it will only need recharging. If you're unlucky it may have split and therefore need replacing which can often mean either taking the boiler off the wall (my preferred way) or replacing the flue due to the location of the vessel.
First diagnose it is the vessel and if so you should find all you need to know in the FAQs.

 

[bluebossa]

Obviously as you said you need to check the pressure relief pipe to see if it's dripping. If it is expansion vessel issues which is most likely you will see the pressure rise significantly when the central heating gets up to temperature.
You may find it's dripping all the time from the PRV as sometimes they don't seal again properly so the pressure rise when hot is the best indication.
If you're lucky it will only need recharging. If you're unlucky it may have split and therefore need replacing which can often mean either taking the boiler off the wall (my preferred way) or replacing the flue due to the location of the vessel.
First diagnose it is the vessel and if so you should find all you need to know in the FAQs.

Thanks for the quick reply, could you tell me where the Expansion tank is located and can it be pumped up as several articles say without major surgery, the model is the 837. Thanks.

 

[ALCPlumbing]

It's on the back of the boiler. There is a schrader valve on it (a normal tyre inflating valve) which to attach a pump to. If you pressurise the boiler then take the cap off the schrader valve and depress the pin, if water comes out then it needs replacing. If not then you need to close the isolating valves on the flow and return connections to the boiler and drain it down using the drain points on the flow and return connections under the boiler. Once it's drained, leaving the drain-offs open, attach your pump (you need one with a pressure gauge), pump to 0.8 bar. The. Close the drain-offs and open the isolating valves. Repressurise boiler and you should be ok.

 

[twgas]

A small amount of water (condensation) coming out the schraeder valve is normal

 

[bluebossa]

So checked it out on the back of the Boiler like you said.

When I pressed the valve some Water did indeed come out.

What I'm confused about though is why the Expansion would fail if it isn't leaking or split - i.e. can it still be re-pressurised

I couldn't get my Bike pump to fit, not enough room around the valve, but wondering if I should still get a new pump and give it a go?

It's been behaving itself for a few days again now, put a little bit of water in.

 

[bluebossa]

So checked it out on the back of the Boiler like you said.

When I pressed the valve some Water did indeed come out.

What I'm confused about though is why the Expansion would fail if it isn't leaking or split - i.e. can it still be re-pressurised

I couldn't get my Bike pump to fit, not enough room around the valve, but wondering if I should still get a new pump and give it a go?

It's been behaving itself for a few days again now, put a little bit of water in.

Spoke to soon, been working for a few days but woke up on 1st January to a Red Light again. Pressed the button and off it went, pressure on the zero again.

Time to ring for a mighty Vallaint Engineer I think as I know I am not up to taking it off and replacing the Expansion Tank.
If anyone knows if its still worth trying to re-pressurize it, even though I don't at the moment have a pump that fits - let me know.

Also anyone know the estimated Damage / Price of a repair like this?
thanks

 

[Bunnyman]

Best is vaillant fixed price repair £260 covers everything it will need

 

[garethdavies]

I have an older vaillant 282 boiler

Last year I had the same problem as you and my engineer fitted a new external expansion vessel that solved the problem

 

[bluebossa]

Called Vaillant and as mentioned paid £260 for a fixed price repair.

This did not cover an Expansion tank which was another £150 if found to be faulty.

Anyhow, to conclude the Engineer said he drained the Expansion Tank then re-pressurized and that all was well.

He also mentioned something else about ignition working but not de-energizing or something similar so two faults diagnosed and no parts consumed.

Boiler firing up happily again now. Many thanks - just in time for more snow!