Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Air separators

JimGPE_3 Member Posts: 240
I'm designing a large (200,000 SqFt) commercial building with hot water heat, with 3" hot water mains in the penthouse boiler room. I have called for manual air vents at all local high points in the piping.

I really cannot see the point of using a 3" rol-air-trol type air separator to initially get the air out of the system, then pay for the pump horsepower to run water through the air separator for the balance of the life of the system.

I have been known to put a smaller air separator in a "sidecar" line, running only some of the water through it when necessary, but I don't see the point in buying and installing a full-time, permanent air separator.

What do y'all do?


  • Eric
    Eric Member Posts: 95

    If sized properly pressure drop pretty low and provides a place for a system strainer leave it in main piping.

    caution with airtrol for 90+% removal typically have to size for 60% of rated flow, see chart for sizing. Also Check out spirotherm one of the best new heating products for air removal.
  • Jerry Boulanger_2
    Jerry Boulanger_2 Member Posts: 111
    I consider a dedicated

    air removal device to be a mandatory element of any closed hydronic system. There are inline air purgers (scoops) available that have negligible pressure drop and do an acceptable job of removing air if they're installed at the high temp/low pressure point - easy to do if the boiler room is on the roof. They also have the necessary tappings for connnection of the expansion tank and the auto air vent, so it saves some fitting.

    'Sidestream' air purgers can take a long time to get even a small amount of air out, especially if the piping isn't tapped into the top of the mains (where the air is). Standard design water velocities do a good job of carrying free air along with the water, so it won't necessarily go where you want it to.
  • Air separators

    Air is the number one enemy in a hydronic system. And try as you might there will always be air entering the system (especially with non-barrier tube). I, like you, have tried to reduce first cost by side streaming a smaller separator (always a Spirotherm)but the velocities are too high to expect the small trapped air to make a right turn into your air separator. Bite the bullet and put in a full sized unit(I recommend a "micro-bubble" over the centrifugal type). The owner will thank you (well probably not, but at least he won't be calling on New Years Day with an air locked system).
  • Josh M.
    Josh M. Member Posts: 360

    I just used a Taco AC-4 for a 100,000 sq. ft. radiant job. I must say I am very impressed! It has an enlarged chamber for slowing the velocity a strainer and a built in baffle. And the pressure drop across it is minimal.
This discussion has been closed.