High pressure problem fixed or not?

[ParaJack]

Hi all, sorry in advance for the long post, but I'm trying to get all the info in:

I have recently been having a problem where when the heating is turned off the pressure gauge sits and stays at 1 bar, the hot water comes through taps/shower etc. as normal. But as soon as the heating is turned on the pressure rises to 3 bar and opens the PRV pumping water outside, then obviously once everything is turned off and cools down the pressure falls to below 1 bar.

What I have done:

I tried pressing the valve on the expansion vessel and air did come out, but no water, which I took as a good sign?!?! I then tested the pressure of the EV and it was around .5 bar.

To get the expansion vessel back up to 1 bar I did the following:

1) Opened a bleed valve on a rad and let water come out until the pressure in the boiler was showing 0.
2) I then tested the EV again to see what the pressure was, it was on 0!!!
3) I pumped the EV up to 1 bar, the pressure on the boiler rose to about .5 bar.
4) I then topped the boiler up to 1 bar with water.

I turned the heating on for about 1 hour and kept a close eye on the pressure, it went up to just under 2.5 bar (but keeping in the green section) and stayed there, I looked outside and there was no water dripping from the PRV pipe outside
I turned everything off and let it cool down, the pressure has dropped back to 1 bar and is staying there. I have tried the heating on/off twice now in the last 12 hours for an hour each time and had the same results.

So my questions are:

1) Have I fixed it or is the pressure still running too high by going from 1 bar cool to just under 2.5 bar when hot?

2) Should I have waited a bit longer until no water came out of the bleed valve when I was lowering the boiler pressure, before I pumped up the EV?

From memory I always thought the pressure didn't go above 2 bar when the heating was on...but I can't be 100% sure on that! I just don't want to keep running it at almost 2.5 bar if it is going to do any damage.

Thanks in advance for any advice.

 

[steadyon]

At your first point 3 you note that the boiler pressure rose as you pressurised the EV. This suggests the system was not "open" at the time you pressurised the vessel, but it should be, otherwise you don't get a true reading of the air pressure in the vessel.

Look at your boiler's installation manual and see what the air pressure in the EV should be. If you can't find it, assume its about 1 bar. Then open the radiator bleed screw and leave it open, then pressurise the EV.

 

[ParaJack]

At your first point 3 you note that the boiler pressure rose as you pressurised the EV. This suggests the system was not "open" at the time you pressurised the vessel, but it should be, otherwise you don't get a true reading of the air pressure in the vessel.

Look at your boiler's installation manual and see what the air pressure in the EV should be. If you can't find it, assume its about 1 bar. Then open the radiator bleed screw and leave it open, then pressurise the EV.

Thanks for the reply, so are you saying I should do this now:

1) Open the bleed screw and wait for the water to fully stop coming out and then leave it open.
2) Pump the EV again until it reads 1 bar
3) Then close the bleed screw
4) Fill the boiler back up to 1 bar with water

Thanks

EDIT*** Forgot to say that all rads were hot from top to bottom when I tested the above.
I'm just worried if I mess with it again it may start going to 3 bar and blowing water out again.

 

[steadyon]

Yes, but don't forget that as you pressurise the EV, the air will displace water in it and you'll get more water coming out of the open radiator bleed screw.

 

[ParaJack]

Yes, but don't forget that as you pressurise the EV, the air will displace water in it and you'll get more water coming out of the open radiator bleed screw.

OK thanks for the help.

 

[Harvest Fields]

What boiler is it?

 

[ParaJack]

What boiler is it?

A Greenstar 30si mate, had the heating on again and pressure when on is now just over 2 bar, when off and cold 1 bar.

 

[dancinplumba]

Don't worry about it

 

[Chuck]

1) Opened a bleed valve on a rad and let water come out until the pressure in the boiler was showing 0.
2) I then tested the EV again to see what the pressure was, it was on 0!!!
3) I pumped the EV up to 1 bar, the pressure on the boiler rose to about .5 bar.
4) I then topped the boiler up to 1 bar with water.

I may have misread / misunderstood your description, but it seems to me that when the EV pressure increased by 1 bar at step 3 then then the boiler pressure should have risen by 1 bar at the same time.

If the gauges are okay, this suggests a blockage between the EV and the rest of the system.