A central heating system inevitably has some air in it which works its way to high points in radiators or pipework and can then be vented using a manual or automatic vent.
But what if that high point is the expansion vessel in a sealed system? How is one meant to vent that. Does it matter? Presumably such air would build up after repeated draining down and refilling.
Andrew
Doesn't that mean, in effect, that you have extra expansion capacity in your system? Some on each side of the diaphragm. If it were mounted with the diaphragm horizontal and the dry side at the bottom, it would be easy enough to tee off to a manual or auto vent.
I have one mounted the other way up though not at the top of the system. But I have an isolation valve and a drain point on the wet side of it so that it is easy to check the pressure and repressurise. I don't recall any evidence of gas buildup the one time I checked it.
To be clear. This is mounted with the dry side uppermost and is at the highest point in the system. The vessel that it replaces was on a tee from a vertical pipe with a vent at the top which was the most common place in the system to get air. There is no vent now - hence my question about the effect of air getting into the pressure vessel.
I don't think it will be a problem - as others have said, it will just be additional expansion capacity.
When you drain it the diaphragm will push the contents out of the bottom so any large volume of air will just go into the pipes. If its set to about 1 bar which most are it won't fill at all until the system is close to full which means you will have vented most of the air.
Have something to add? Share your thoughts — no account required.
Ask the community — no account required