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Proper air elimination

HVACLIFE Member Posts: 2
Hi yall. I am still somewhat new to the boiler world, but i absolutely love it. I have found my calling....and its hydronics. I was just at a commercial building that had a no heat call. The system is using 4 compression tanks piped in off a common header. The tanks are piped in before the suction of the pump. Boiler, tanks and piping is on the roof. When i first went to the site 2 out ofnthe 4 comp tanks were waterlogged, the other 2 had basically no water in them. Pump discharge was over 70 psi, pump suction was 40 psi, boilers were around 25 psi....all these stuck out as way too much pressure in the system and im not getting rid of the air thats entrained ( recent work was done and i feel that they let in tons of air without purging) the system feeds to AHU'S on the different floors, that feed coils for different zones. There are coin vents on the supply and return headers at the individual coils. Actuators are on each coil return piping. Unfortunately they way it was piped, there are no iso valves for the comp tanks, nor the system pipe that ties into the comp tanks. I am curious if yall could help me understand a little more and provide solutions to present to the customer to get this system piped in properly with components to ensure reliable operation. I will obviously answer any response and or further questions. Thank you all. I value input from huys who know hydronics and want to help someone learn a thing or 2. I love hydronics, love to learn and strive to be a better, more understanding tech.

There is a drain line that comes off the header for the compression tanks, but no real isolation from the system itself 


  • hot_rod
    hot_rod Member Posts: 22,327
    How tall is the building. The static pressure you read at the bottom relates to how high you need lift the water from the bottom of the piping to the highest point. You have 25 psi at the top?

    The other pressure is dynamic pressure, the pressure the pump adds to overcome the piping resistance around the piping circuits.

    Any air that is purged out should be piped into the compression tanks to maintain the air space for expansion.

    Download the Amtrol Engineering Handbook for good explanations on tanks in general.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream