Baseboard heating (air in pipes?)

Brad White

You would hook up a hose to those valves ("C") as the outlet hose and by closing all other zone isolation valves ("A" for the domestic heater and "B" for the other circulators). Your water fill valve would be forced fully open and the out of the active "C" valve until it runs clear of air. Repeat for the other zones, one at a time in order to maintain highest velocity in each zone while purging. Run the hose to a clear outside area to witness the clarity of the water.

A helper should shut the "C" valve and the fill valve at just the right times to avoid setting off the relief valve.

In lieu of this, you can always install needle bleeder valves at the system high points but this carries some risk of leaks.. Personally, I like baseboard tees and/or bona-fide key operated vents at high points...

<b>But, I have to say, you are only treating the symptom, ignoring the cause. </B>

See that large gray hanging tank? That is the expansion tank. It is on the outlet of the boiler and the circulators ("pumps") are forcing water toward that tank.

Where that tank connects is the "point of no pressure change" by definition. Those circulators want to impart a difference in pressure across them. (Ahead of the circulators is a large pipe and large-passage boiler. Not a lot of resistance.) Now, the circulator is not smart, it can just force a difference in pressure. If the outlet pressure cannot change then the suction pressure has to. (With me so far?) This pressure can often be sub-atmospheric. Air can be sucked in via valve stems, automatic vents, any air-penetrable orifice that can still hold water.

The expansion tank should be moved to the suction side of the circulators (not an easy task with all of those circulators!). The ideal is that the circulators would be moved to a location just downstream of the expansion tank.

The installation you have is a common one. While it may look neat and orderly it violates a fundamental principle of successful hydronics. The fact that you have air in a system with no internal source of air means it is coming from somewhere...

Jeffk

air in baseboard heating system?

I have baseboard heating and most of the zones dont seem to be working this year. I suspect air in the pipes - any pointers on bleeding the air out?

There are no bleed valves on the baseboards just this setup in the basement (see attachment)


by the valves labled "C" are where you can connect a hose. Anyone know the right valve sequence to purge all the air out of the 4 zones?

i thought thats what the grey tank with the little valve above it was supposed to do but if so, its not working.

thanks

Jeffk

thanks - moving the exp. tank is way beyond me (obviously).

So the order would be:
close A and all B's except the 1 zone i'm working on, open C on that Zone until clear of air, then repeat for the other zones?

Brad White

Yes

That is about it. You could also close the valves marked "D" (except for the zone you are working on) in order to keep the pumps full of water and not get those air-bound or in need of a purge themselves.

I do not know what valve "E" does.

Your fill valve location is not clear to me but if downstream of "F" (the main isolation valve), I would close that too, IF the boiler is locked out at the service switch. I try to keep as much piping full and under pressure as I can, the better to focus the purge on the zone I am working on.

If you have an isolation and drain valve for each zone on the supply side, I would use that as the inlet flow valve and purge back towards the return or the other way, again, the better to spare uninvolved piping from being disturbed.

Not the only way to purge, but is logical. Others may well have other tips too.