Pressure problems

[Bucky31ni]

Have 7 yr Vailliant ecotec plus 937, serviced yearly. Boiler after 45 mins reaching 2.7 bar I then turn it off! It then takes 3 hrs to return to 1.2. Any ideas what’s going on?

 

[Deleted member 120897]

Sounds like you’re “service” is a safety check. You likely have an expansion related issue, either the vessel or communication pipe.

 

[Bucky31ni]

Vessel replaced March, pipe checked nothing untoward. They suggesting an external vessel be added!

 

[Deleted member 120897]

Vessel replaced March, pipe checked nothing untoward. They suggesting an external vessel be added!

How big’s the system?! Haven’t had it myself, but the new vessel could be flat already?

 

[Ric2013]

Vessels are weird things. The one in my father's boiler (then 10 years old) went flat 10 years ago. I re-pressurised it and it's been fine ever since. Quite how it went flat and why it hasn't gone flat again...?

 

[Bucky31ni]

18 Rads, 8 double

 

[Ric2013]

Did you not used to have this problem in the past and have you added radiators or extra pipework since such time?

If it worked in the past and nothing has changed it should still work now without an extra vessel being added.

 

[Bucky31ni]

Did you not used to have this problem in the past and have you added radiators or extra pipework since such time?

If it worked in the past and nothing has changed it should still work now without an extra vessel being added.

Agree, worked great for 6 yrs nothing added since

 

[Ric2013]

I'd assume insufficient pressure in the expansion vessel and would want to verify. Should be much the same as (some say slightly above) the pressure of your primary water circuit. BUT to check you need the primary water circuit to be void of pressure. I would hope the installer checked, with an accurate tyre pressure gauge or similar device, that the vessel was pre-charged to 1.2 bar (if that's your primary water pressure when dead cold) when he installed it. Did he, or did he just assume the pre-charge was correct?

 

[John.g]

18 Rads, 8 double

You probably have a 10 litre EV.
If prefilled to 0.75bar and filled to 1.2bar then it would require a system contents of 170 litres to rise the pressure to 2.7bar with average of flow/return temps of 65C, unlikely that your system is this big, if say 140 litres max then the final pressure above for the same conditions will be 2.25bar. If pre/filling of 1.0/1.2bar, final pressure, 2.06 bar.

But if the prefill has fallen to 0.4bar then a fill pressure of 1.2bar will result in a final pressure of 2.7bar.