Air In Hot Water Baseboard

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    • #274167

      Whats the recommended way of purging air out of hotwater base board heat? I have installed automatic air vents on top floor baseboard units but I still keep blowing the safety off. I already checked feed water reg and thats ok. Expansion tank is set for 12#. Pressure keeps rising in system though. How long does it take for system to stabilize?

    • #289281
      Harold Kestenholz

      Air in the system is not the cause of blowing the safety relief valve. Not enough air in the expansion tank is the cause. Either the tank has lost its original air charge (void of water when disconnected from the sytem) or the tank was not large enough in the first instance to accept all the extra water produced by heating the system volume. You can read an explanation of this design problem in the free lessons section of :

    • #289282

      I took the expansion tank off and drained the water from it. It was about 1/3 full. I recharged it to 12# and reinstalled it. I filled the system up with water and now twice Ive had to release some water, about 3/4 of a gal at a time to bring the pressure back down. I set the aquastat to 160 but it keeps firing till about 180. The differential is set for 15#. What pressure should I be looking at if the water is 160 degrees? Is there an acceptable range?

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