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Boiler not developing much pressure and how to bleed??

Had to replace a baseboard tube/fin section. I drained boiler and zone needing repair. Installed new section- done
My problem is now that I opened fill valve to fill but I don't know when it is filled enough. So I filled it for about 45 seconds. Now when I run the boiler and call for heat from the non repaired zone, I only get 5 psi and a lot of water running noise, air noise going into exp. tank, but I do get heat. With the boiler off should I open the fill valve until I get 15 or so psi? I get 0 pressure when I was filling. It only rises to 5 when it is running.
Next- how do I bleed air from zones without air vents in baseboards??
Here's how the system is setup
Buderus boiler, 3 zones. From supply side of boiler to air separator which is piped to exp. tank. other side of air sep goes to a manifold with 3 different zones each with isolation valves. Through baseboard heaters and back to manifold for 3 zones with Honeywell control valves for each zone of course. There is a faucet drain under this manifold - I assume for bleeding. This then goes to B/G pump then to return side of boiler.
How do I get the air out?
Thanks all


  • Timco
    Timco Member Posts: 3,040

    Where to begin...First, start with a cold boiler. Then, find your boiler gauge. Fill the boiler to 25#. Attach a hose to the drain on the manifold you described, an open the drain valve. Woosh!!!Do this while the boiler is filling...just open at 25#. After the big purge, leave the boiler filling until no air comes out the hose. After all this, fill the boiler to 12# cold, and fire her up. Expansion tank should be filled to the system pressure prior to filling the system. If it will not hold a 'charge', then you need a new one. Open only one zone at a time to purge it, then close it and do the next...


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