Worcester 28CDI how do I check expansion vessel pressure?

[ABN]

Hi

Switched on the central heating today to make sure it was working for the winter.

Turned the water temperature setting fairly low and swiched it on. The pressure went from 1bar to over 2bar even at the low temperature setting so would like to check the expansion vessel pressure.

I assume its the valve on the left at the top of the boiler. However its oversized to fit a normal tyre pressure guage/pump to. Even it the guage would fit there is no central pressure release pin so wouldn't be able to measure the pressure.

Am I looking at the right thing and if so is there an attachment you need to buy to allow a normal tyre guage/pumps to fit?

 

[gaswizzard]

You sure your not referring to fan pressure test point.

 

[flameport]

I assume its the valve on the left at the top of the boiler

It isn't - that is for flue gas sampling.

The pressure vessel is inside at the lower back of the boiler, behind the pump. It has a standard valve, which a car tyre pump will fit onto directly.
You will need to open the lower panel to get to it (the panel with the control knobs on).

 

[ABN]

Think your possible right. Just managed to download the manual for it and think what I'm looking at is the automatic air vent. Strange that an air vent has a plastic screw on cap.

Nothing in the manual that shows exactly where the valve is but have removed the front cover and there does seem to be a car valve thing on the expansion vessel. The water pump is directly in front of it making access very difficult, infact impossible for the pressure gauge/pump that I have

So is the one on the expansion vessel the one I should be looking at and is there a "trick" for testing/filling it?

 

[ABN]

Sorry flameport slow typer was replying to the other reply while you were posting.

Only had to remove the white front cover to see pump and valve not the grey plastic controls cover.

So the one I'm now looking at isn't the right one either?

 

[ChrisOxford]

The expansion vessel is usally a big red tank and has a normal car valve on it. Do a Google image search for: 28cdi expansion vessel to get an idea of what it looks like.

To check its charge pressure (about 0.5 Bar - see the Manufacturer's Instructions for the actual figure) you need to de-pressurise the boiler.

As you've found out, the other similar valve is on the auto air vent. Don't touch that, and note that the cap should be left on but unscrewed a turn or two.

 

[ABN]

Thanks

The big red thing I'm looking at is the expansion vessel then. Assume therefore that the valve on it is the one I should be checking.

Just need to find a way to get my tyre pump/gauge on it as its directly behind the pump.

Don't like to make things easy for us do they

P.S. have now lossened the cap on the auto air vent re your suggestion