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How to purge air in system without return shut off valve?

fingerlakes
fingerlakes Member Posts: 3
in Radiant Heating

My system has 5 zones and I've been able to purge the air out of the zones with radiators since they have bleeder valves on them. But zone 1 is a closed system with no bleeder valves on the copper pipes. This zone is full of air and I can't bleed it.

I've looked everywhere but my system does not have a return shut off valve into the boiler!

Pics of the system: https://imgur.com/a/radiator-system-AL3wHvF

Everything I've researched says to:

  1. Turn off boiler
  2. Close return water valve into boiler
  3. Open zone valve to purge
  4. Open water fill valve
  5. Open purge valve and let the air circulate out.

I appreciate your insight!

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,596

    You have an air scoop on the supply from the boiler. The expansion tank comes out of the bottom of the air scoop and the air scoop needs a good air vent on top of the air scoop. I can't see if there is a vent there or not.

    Replace the air vent on top of the air scoop if there is no vent or the vent doesn't work. Then fill the system with all zone valves open and bleed all the radiators. That will get most of the air out.

    Then close all the zone valves except 1 and start the boiler and circulator and the air for that zone should come out the air scoop vent. The shut that zone valve and open another zone valve and repeat this with all zones and the air should eventually work its way out

  • DCContrarian
    DCContrarian Member Posts: 728
    edited November 6

    Is the closed zone the indirect water heater loop? I would think that would come out because it's lower than the rest of the system. There's almost no vertical difference between the supply and return height so the smallest amount of pressure should let water flow.

    Have you tried opening all of the zones and letting the circulator run? When the air comes out, it has to go somewhere, it's going to go up into the other zones. That's why you want them open. The you'll have to bleed the air out of them.

    Another thing to try is closing the makeup water supply, closing the zone valve for this zone, opening the boiler drain to let off pressure, and then attaching a water supply to the hose bib on this zone. With the zone valve closed that water has nowhere to go but through the loop and out the boiler drain, taking the air with it. Again, the air is likely to end up in the higher zones.

    The long term solution is to install more valves. But presumably it's worked before so it's possible to get it working as is.

    Also, is that 45 PSI on the gauge? That's awfully high. Is your pressure reducer working? If you have to drain the system to replace it that's a good time to add a few more valves. I'd also add one on the expansion tank so it can be replaced without draining the system.

  • fingerlakes
    fingerlakes Member Posts: 3
    https://forum.heatinghelp.com/discussion/comment/1818431#Comment_1818431

    The zone is question is not the water heater loop.

    When I was venting the radiators, I did have all the zones open with the boiler on. You mention that the air is likely to end up in the higher zones. The zone that I can't purge is the 2nd floor, so I think all the air is stuck there and won't circulate out.

    The 45 PSI gauge is my well water pressure gauge. Sorry for the confusion. 15 PSI on the boiler.

  • fingerlakes
    fingerlakes Member Posts: 3
    https://forum.heatinghelp.com/discussion/comment/1818430#Comment_1818430

    Yes, the air scoop (now I know what that is) has a vent on the top. I will try opening the air scoop and filling the system as you recommend.

    Should I ignore the hose bib valves by each zone valve then? What is their purpose?

  • Grallert
    Grallert Member Posts: 805

    You might be able to purge it backwards using the zone valve as a shut off.

    Miss Hall's School service mechanic, greenhouse manager, teacher, dog walker and designated driver

  • DCContrarian
    DCContrarian Member Posts: 728

    "Should I ignore the hose bib valves by each zone valve then? What is their purpose?"

    They're put in both for draining and purging a zone. But they're kind of in a funny spot. Normally what you do is put them on the return and a shutoff immediately afterwards. If you open the zone, close the shutoff and open the hose bib water will run freely through the zone and out the hose bib, taking air with it. It helps to open up the pressure reducer so there's more flow.

    Where they are now they can kind of be used the same way if you close the zone valve, feed through the hose bib and let water out through the boiler drain. All the flow has to go through the circulator which might limit the flow but you might be able to get enough flow to push out all the air.

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