Fitting a new expansion vessel

[lukewarmbath]

Hi all - I'm new to this forum having used the screwfix one which is now effectively unusable.

I just replaced an expansion vessel on our heat store. The question arose as to how to bleed the air out of the "water" side as it is vertically mounted with the compressed air side on top and the "water" side underneath. After mounting the "water" side is still full of air so is effectively a "dead leg" in the system - not good.

I thought about mounting it "upside down" (i.e. "water" side at the top) which would hopefullly fill with water when the system was bled normally.

Any thoughts or comments? I have to say that "wetpants" on the screwfix forum was very helpful.

Thanks

lukewarmbath

 

[Googlyhead]

Does it actually matter? The vessel will allow the necessary expansion volume regardless of what is in the non-air side, and the 'dead leg' doesn't lead to a tap or anything. It's been argued that the benefit of mounting in such a way is to isolate (and thus protect) the internal membrane as far as possible from the heated water.
Any air in the system isn't going to spontaneously multiply! There will probably be an auto air vent nearby anyway should any more get in. You could also consider the fact that the air volume in this particular 'dead leg' is going to be greatest at time of install, compressed when the system is put under pressure.
To bleed; I suppose undo the nut at the vessel to release air from pipe until water reaches it. Can't see how to fill the vessel itself.

 

[adlplumbing]

don`t bled the expasion vessel its meant to have air in it
if goes flat the pressure will rise and the prv will let water out of it

 

[lukewarmbath]

Thanks for that googlyhead. Well the expansion vessel is actually in the DHW side of the heat store HEX - its an advance appliances vented heat store - so the "deadleg" is actually in the DHW tap supply. Having seen the inside of deadlegs in the past, they have had unspeakable gunge in them which i wouldn't like to have my tap water passing over - even if they are hot taps! But I take the point - expansion-wise its fine as is.

lukewarmbath

 

[lukewarmbath]

To adlplumbing - please note I am talking about bleeding the WATER side of the membrane in the expansion vessel! Obviously I would not bleed out the compressed air from the air side!

lukewarmbath