Checking pressure reading is correct on gloworm 35ci

[tawelfryn]

Hey all,
I have a gloworm 35 ci.
Now I have changed the prv, and correct me if im wrong these are set at 3 bar. I have checked expansion vessel, 1.6 bar there.
I notice Im losing pressure through prv, when display is showing around 2.4ish bar. consequently, water is lost, and pressure (on the lcd) goes to below 0.5 when cold, boiler shuts off due to thinking it has low pressure. I think it could be around 1-1.1 bar in the system, but the lcd, is reading low, to what is really in there. Does this sound feasible to you guys?
If Im on the right track, whats my next port of call?
change pressure sensor?
Cheers

 

[chrishutt]

Firstly, the expansion vessel air pressure of 1.6 bar sounds rather high. 0.8 bar is more typical of the precharge pressure. Are you sure you're measuring the air pressure with no system pressure applied?

Secondly, I take it you don't have a mechanical pressure gauge on the system to compare with the LCD displayed figure. If you could fit one (temporary connection via filling valve?), you would then know if the LCD display was accurate or not.

 

[tawelfryn]

Hi Chris,
Yes 1.6 bar with no system pressure. Its what the manual says it should be.
Good idea on the mechanical pressure gauge, trouble is the filling valve is incorporated, (blue turn knob) could I take the prv off temporarily, and put a mechanical gauge there?

 

[chrishutt]

Pressure gauge could be anywhere on the system - a radiator air vent tapping might be the easiest location. If it's on the same level as boiler it will give the same reading, providing the pump isn't running.

I'm surprised at the expansion vessel precharge pressure? Is the boiler low down in a system over several floors?

..just checked the manual for your boiler. It says expansion vessel precharge pressure should be 0.5 bar. Where did you get the figure of 1.6 bar from?

 

[tawelfryn]

Ok thanks Chris, I will see if I can attach a mechanical pressure gauge, somewhere, to see what the pressure is at cold. Got me thinking now about the expansion vessels precharge. Almost sure it was 1.6 unpressurised. I WILL check my correspondence again, may have made a mistake
The boiler is on ground floor, supplying ground floor, upstairs, and one rad in attic conversion.
If after checking with mechanical gauge, and the boiler is reading low, is it the pressure sensor needing changing?

 

[tawelfryn]

Sorry, Chris, me and my memory, you are right, I meant 0.6 bar, is what my reading was, Too many bars in my head!