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.

Need help on how to purge the air out of one of the zones

johnwall Member Posts: 4

I would like to purge the air out of one of the zones and need some assistance. First, please allow me to explain if my understanding of my boiler heating systems is correct. From the attached pictures, I draw blue lines show how the water flows into to boiler from the street and after the water is inside the boiler, the boiler heats up the water and then supplies(red line) the hot water to the baseboards and then returns back(black lines) to the boiler for reheating via those zone valves. Please let me know if my understanding is correct and If I want to purge the air out of that one of the zones(circles in blue), can you please tell me what steps need to be taken?
Any help will be much appreciated!!


  • Snowmelt
    Snowmelt Member Posts: 1,394
    From the looks of it, make sure that zone is off, then hook up a washing machine hose hook it up to the hose bibs then just drain away. Repeat all zones till you feel all air is out.

    The one reason you have air in the system is because that air scoop isn't really used corectly you need a taco 4900 residential, that would work the best.

    Also move the expansion tank to other side of pump.
  • icesailor
    icesailor Member Posts: 7,265
    In the second photo, there are three zone valves, two to the left, and the one farthest to the right is split with two returns. Is one of the returns that is split on the right, the zone that isn't working? Is one of the two return pipes hot and the other isn't?

    There are two zone valves to the left. Are all zone valves open? You have to check.

    Is the not working zone on the second floor and you turned the heat way down? If you did, it might be frozen up.

    IMO, if the system was working properly 30 days ago, and it isn't working now, the placement of air elimination etc. has no bearing on your problem.
  • hot_rod
    hot_rod Member Posts: 19,927
    Is the system noisy? How do you know you have an air problem?

    I agree with Ice, air problems don't usually start for no reason if the system has been sealed and closed.

    While not ideal that air scoop will remove most air, be sure the brass vent is not stuck or plugged. Press down on the stem inside to assure it vents.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • johnwall
    johnwall Member Posts: 4
    Hello all,
    Thank you for all your responses! I guess the issue that I am having is more complicated than I thought. Let me provide some more information. So there are 3 zone valves, the one on the left is for the basement, the middle one is for the 3rd floor(duplex of the 2nd floor) and the one on the right(has the split returns) is for the second floor. The 2nd floor has the twice the area of the 3rd floor so there are two sets of baseboards (two returns)

    Last week, the zone for the basement stopped working and I noticed the zone valve was very hot when I was touching it, so I replaced the valve motor only and it worked. However, now it stopped working again. When I turned the heat on and off for that valve, I could hear what appears to be that the motor is doing “closing” and “opening”, and plus I just replaced the motor last week, so my guess is that most likely it’s not the issue with motor this time. The other two zones are working fine, although I do hear the “bang” sounds whenever I turn on the heat on the 3rd floor.

    Therefore, the first step I would like to do is to purge the air out of that zone first. Should purging the air from that zone be sufficient or I need to purge the other two also? For purging out the air, should I just turn off main power for the boiler, I assume after the power is off, the valve will be off also? Then drain the water from the spigot?

    Once again, any comments or help will be much appreciated.

    Thank you!
  • Snowmelt
    Snowmelt Member Posts: 1,394
    Here is what I would suggest you. I'm personally not good with all that low voltage wiring. So I would get a switching relay. Most likely at your stage I would get it with outdoor reset. So that would be s.r. 503 o.r. That's three zone switching relay with outdoor reset. That identifies what's calling for and what's working or not working in the system. At the same time it gives you the abilility to hook up out door reset.

    I would do it with the power off. Do all three or four. But I'm telling you I don't like the scoop, I don't think you have 18 inches of straight pipe before the scoop. I like to see an air seperator.
  • Paul48
    Paul48 Member Posts: 4,469
    Snowmelt......Does that work with zone valves?
  • Snowmelt
    Snowmelt Member Posts: 1,394
    My fault you need a zvc 403 expandable with a sr 501 or
  • todd_ecr
    todd_ecr Member Posts: 91
    John, I think you emailed us earlier as I noticed another guy in out Tech dept had those pictures on his computer.

    In addition to leaving the zone valves closed and opening the purge valves, you will need to maintain pressure in the system during the purging process. If the pressure reducing valve can't keep up with maintaining pressure, the purging process will get very frustrating as you will need to constantly stop to wait for the pressure to come back up.

    Those of us that are experienced with purging get around this by opening the fast fill on the pressure reducing valve. This will increase pressure and speed up the process. It also requires frequent monitoring of the gauge. If you don't closely monitor the gauge you could over pressurize the system to the point that the relief valve will pop and discharge water. If this happens you may very well end up needing to replace the relief valve.

    My suggestion is to find a reputable contractor in your area. You could be making things worse for yourself if you attempt something like this. I don't mean to be doom and gloom but a lot of us who have had service calls where you go to do something fairly easy like purging air from a system end up finding other issues(bad or clogged pressure reducing valve, bad air vent, relief valve and expansion tank problems).
  • Snowmelt
    Snowmelt Member Posts: 1,394
    Todd nice feed back.
  • icesailor
    icesailor Member Posts: 7,265
    edited February 2015
    Any zone that is getting hot DOES NOT NEED TO BE PURGED!!!!!!!

    If you had a zone valve that stopped working, and the motor was hot, so you replaced the motor, and now, that same zone has an issue, you need a new zone valve. Those zone valves don't have a lot of resistance for the motor to overcome. If there is high resistance (hard to open manually), it will kill the motor.
  • johnwall
    johnwall Member Posts: 4
    Once again, thank you all very much for the feedback!

    Just for the sake of my own knowledge, I have one final question. I see only one zone (2nd floor) has the water valve on one of the return lines. Should all return lines need to have one so that we can shut off the water valve when purging the air/water out? My understanding is that once the water valve in the return line shuts off, it will ensure all the air/water to be purged out during purging process otherwise, the air/water will still travels through the return line and flows into the boiler?

    Thank you!
  • bmwpowere36m3
    bmwpowere36m3 Member Posts: 512
    All the zone returns have zone valves, basically electrically powered valves (open or closed). When there is no call for heat on a particular zone, that zone valve should be closed. If the zone valves are working properly, you should be able to purge by having the zone valves closed. However having a dedicated valve (i.e. ball-valve) would be a good thing from a reliability/ease of purging standpoint.
  • johnwall
    johnwall Member Posts: 4
    Understood. Thank you "BMW"!