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Air constantly in indirect hot water loop

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RMatty
RMatty Member Posts: 5
Hi guys I’ve been having an ongoing problem with air in my indirect hot water loop. It never has been air bound but every time the boiler satisfies I can hear air crunching through the circulator when it’s quiet. It’s a newer Buderus with a 30 gallon Buderus indirect. Pumping on the supply, with a Spirovent. I’ve purged it and doesn’t help. Any suggestions would be appreciated.

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  • Jamie Hall
    Jamie Hall Member Posts: 23,567
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    Remember that air can enter a system only is there is a location where the pressure is below atmospheric and there is an opening. I presume there is no leak, but I will ask where the expansion tank is located in relation to the indirect and the Spirovent and the circulating pump intake.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 22,396
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    Try boosting the fill pressure to 20- 25 psi, let it run for 20 minutes or so and lower pressure to 12- 15. Keep an eye on the boiler pressure gauge, if it creeps to 28, allow some pressure off. Don't want to pop the relief.

    The extra pressure will often squeeze the bubble size and circulate it back to the purger.

    Pump on the highest speed also for a good "scrubbing" flow.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • RMatty
    RMatty Member Posts: 5
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    Hi thanks for the suggestions… Jamie the x tank is before the spirovent and circulators…essentially pumping away from the x tank. It goes fill valve, expansion tank, spirovent, then circulators all on the supply side of the boiler. I’ve attached some pics of the setup. And no there isn’t any leaks have had the fill valve off for weeks no pressure change.
  • HVACNUT
    HVACNUT Member Posts: 5,876
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    Is thermal purge set up on the Hydrostat?
    Is that a black tee on the domestic hot?
  • pedmec
    pedmec Member Posts: 994
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    Are you sure what your hearing is air? When you purge the loop are you purging into a bucket of water so you can see air bubbles?
  • RMatty
    RMatty Member Posts: 5
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    No thermal relief… It’s air once in awhile I hear the spiro let air out but it seems the majority of the time the air blows right past the Spirovent. Also it sounds like rain in the pipe at certain times but only in the indirect loop the two heating zones are quiet as a mouse. Is it piped correctly?  I’m going to try purging into a bucket this time. Is it best to purge when hot or cold? Knowing to be careful of the hot water when purging.
  • mattmia2
    mattmia2 Member Posts: 9,850
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    Every time you purge you add more air to the system in the form of the air that is dissolved in the fresh water. Maybe manually turn on a heating zone or 2 while the tanlkess is calling so some of the air gets mixed in to that part of the system so it will have more opportunity to get removed. Maybe it rarely sees cold enough water in the indirect loop to absorb much of the air because of the tank temp.
  • RMatty
    RMatty Member Posts: 5
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    I’ve actually wanted to do that but the indirect is on priority so when it calls the heating zones shut off until the dhw is satisfied.
  • bucksnort
    bucksnort Member Posts: 167
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    RMatty said:

    I’ve actually wanted to do that but the indirect is on priority so when it calls the heating zones shut off until the dhw is satisfied.

    Turn off priority
  • RMatty
    RMatty Member Posts: 5
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    Thanks I’ll give it a try…Is that as easy as going into the Taco 3 zone switching relay and switching off the priority switch for Zone 3?