vaillant ecotec 831 pressure loss

[Gordon-R]

Inastalled 2015 no pressure loss issues till Jan 2023 lost pressure overnight F22 low pressure
Recharge back to 1.8 bar
Lost again overnight end Feb2023
No system leaks
Re[placed Heat exchanger internal leak and recharged expansion vessel under warranty
Ok till Nov 2023 losss again overnight
Loss again Jan 2024
Drop test for 3 hrs only 0.1 bar loss
Vaillant say system leak but each time no damp or water seen antwher inc under carpets etc
Could it be pressure relief valve but no water at discharge point
Can anyone help?

 

[terryplumb]

Are any central heating pipes buried in concrete,or below ground floor in a void ?

 

[Wayners]

I should leave this thread to plumbers but I know you can pressurise boiler and turn off isolation valves at the bottom. Also switch boiler off. If no internal leak boiler pressure won't drop.

You will know it's house pipes

 

[Johntheo5]

Inastalled 2015 no pressure loss issues till Jan 2023 lost pressure overnight F22 low pressure
Recharge back to 1.8 bar
Lost again overnight end Feb2023
No system leaks
Re[placed Heat exchanger internal leak and recharged expansion vessel under warranty
Ok till Nov 2023 losss again overnight
Loss again Jan 2024
Drop test for 3 hrs only 0.1 bar loss
Vaillant say system leak but each time no damp or water seen antwher inc under carpets etc
Could it be pressure relief valve but no water at discharge point
Can anyone help?

With is the cold pressure now and what is the highest you see or saw it with all systems hot?.

 

[Gordon-R]

Hi all thanks for responses
No pipes buried in floor. no damp platches on ceilings. Solid ground floor no signs of damp under carpets wher pipes come down hidden
Normal pressure is at 68deg flow temp is 1.8bar.When drop test done it was set to 3bar. Only lost 0.1bar after 3 hrs. But temp drop could cause that i think.
When pressure lost 0.4bar from overnight cooling down to 1.2bar approx this is about 1 - 1.5 litres of water. but ive never seen a leak
Hope this helps me get help

 

[Johntheo5]

You realise that its quite normal for the pressure to drop when cooling down, for example if a 100L system at a average temperature say 60C cools down to 15C then the expanded vol will be 1.62L so assuming precharge/filling pressures of 1.0/1.5bar will result in a hot pressure of 2.13bar & cold of 1.5bar, if the precharge/filling pressures are the same at say 1.2bar, the hot pressure will be 1.63bar & cold 1.2bar
Assuming a 10L EV.

 

[Gordon-R]

Thank you yes appreciate pressure drop overnight with temp cool down drop.
When my boiler loses pressure from 8.30 pm switch off at say 1.8bar at 6.30am failiure to start as pressure is 0.4bar no signs of water loss on sysyem or PVR drain very strange. As you say 1.6L of water is a lot not to find a leak.

 

[Gordon-R]

Not as if pressure /water loss happens daily or weekly last ime 9th Feb till 21st Mar

 

[terryplumb]

Thank you yes appreciate pressure drop overnight with temp cool down drop.
When my boiler loses pressure from 8.30 pm switch off at say 1.8bar at 6.30am failiure to start as pressure is 0.4bar no signs of water loss on sysyem or PVR drain very strange. As you say 1.6L of water is a lot not to find a leak.

You don't need to loose anywhere near 1.6 litres of water for system pressure to drop to 0.4 bar.
Do you experience regularly a build up of air in radiators ?

 

[Gordon-R]

No we dont have any air in radiators never have since this boiler installed. Used to get it all the time with old boiler with open vent and header tank.

Also went from may 2015 when boiler installed to Jan 2023 with no pressure loss ever.
Since then lost pressuse 24 feb 23, after which heat exchanger replaced due to internal leak
Then pressure ok until 24 nov 23, again 30 dec 23, 9 feb 24, and last time 21 mar24.

 

[Johntheo5]

Could it be pressure relief valve but no water at discharge point

Can you tape a plastic bag around the end of the discharge pipe.

 

[Gordon-R]

Yes already done but when previous pressure drop outlet is adj garage door easy to see if wet on concrete

 

[CBW]

Have you seen inside the boiler or just Vaillant engineers? Has it been isolated as per @Wayners above?

 

[Gordon-R]

No i havnt yet only valliant eng. he did drop test isolation and although he drained off to cool down before test he only drained from 1st floor as all ground floor feed from above due to solid floor. Therfore when he tested after 3hrs it had only lost 0.1bar. This in my opinion could be due to temp drop from undrained section of system.
As Gordon-R 24th march im thinking of writing th valliant suggesting they may have a falty batch of heat exchangers with internal leaks. dont expect ill get far.
I intend to look myself into boiler as soon as cold weather over. "My wife always freezing"
Any more ideas will be most welcome

 

[jurassic sparkk]

Was inhibitor put in?

Even a small weep can drop pressure....