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Heat in one zone not working well

phnickphnick Posts: 15Member
Hello, thanks so much in advance...

I have a three zone boiler heating system. All of the sudden one zone does not work well. The heat turns on from the thermo, stays on for 5 minutes and goes off. I have tried a bunch of stuff...

1. I bled the zone, made no difference
2. I just bypassed the thermo by connecting R&W to keep it calling for heat, the baseboards get hot then shut off after a few minutes.
3. I tried forcing open the zone valve to test that, even in manual open mode the baseboards stay warm, not hot

Nothing seems to help, the other two zones work perfectly. This zone just gets warm and stops getting warmer. The zone pipe and return pipe are both hot to the touch, so the water is making the trip around the system.

Any advice on what to try next would be greatly appreciated.

Thanks, Nick


  • SuperTechSuperTech Posts: 938Member
    Sounds like you may have air in the lines for that zone. I would try to purge the zone until you get a continuous steady stream of water through the hose.
  • Intplm.Intplm. Posts: 684Member
    Sounds like you almost have it.Try purging by putting the end of your hose at the bottom of a bucket. Put the bucket outside. PURGE filling the bucket. Watch for air bubbles both large and small rise to the top. Do this till NO bubbles rise from the bottom of the bucket. This should help eliminate all the air.

    Seems that you know ? What you are doing. If the above is confusing. Post some pictures. Then we might be able to help from there.
  • phnickphnick Posts: 15Member
    Thank you so much for your reply.

    So, I did purge it, but probably not enough. I just want to confirm I did it correctly.
    1. I close the returns for the working zones.
    2. close return for the bad zone
    3. Open the spigot on the troubled zone, and crank the heat in that zone.
    4. Drain water in bucket until I see no bubbles
    5. Turn off spigot and reopen all returns

    I ask because I did this and as I was reopening the return there was a loud clanking noise in the tank area.

    Thanks again, Nick
  • Intplm.Intplm. Posts: 684Member
    Ok.....almost! Turn the power off.

    Open the feed water to the boiler through the zone needing the purge.


    Check for bubbles.
    If no more bubbles.....put the boiler back to normal.
    Turn the power back on.
    Set the t-stat to the purged zone all the way up.
    The other t-stats all the way down.
    Grab the purged zone with your hand on that return closest to the boiler. If you can't keep your hand on the pipe, you have purged that zone successfully.
    If you hear noise in the zone or the pipe stays cold you have not purged enough.

    Questions? What caused the need to purge?
    What type of air separator do you have on the system?
    Is this a reoccurring problem?

  • phnickphnick Posts: 15Member
    Thanks for your continued support.

    OK, so when I did the purge I definitely so a bubble or two, but nothing significant. I let a full bucket run, then I turned the system on and cranked the heat in the troubled zone. The return pipe got very hot pretty quickly, then become warm (I was able to grasp it), then after the system ran for about 3 minutes there was a clicking off, the system stopped heating up, and I watched the zone valve close as if it was done. I checked the thermo, it is absolutely still calling for heat.

    This is the first time this happened in the 2 years living here. Nothing changed in the system before the problem occurred but some electrical work on the circuit the system is on. HOWEVER, the other zones stay on and work perfectly fine.
  • Intplm.Intplm. Posts: 684Member
    May not have purged long enough. I have purged some zones 15, 20, and thirty minutes or longer.
    Post some pictures of your system. Maybe we can get a better idea of what's happening.
  • phnickphnick Posts: 15Member
    Thank you. I will try and purge again for longer. I have attached a pic too.

    I just want to make absolute sure I am purging correctly. I turn OFF the two good zones and close their returns. I keep bad zone’s return open. I open spigot for bad zone’s return to begin draining. I turn the heat up high on bad zone to call for heat. I let water run for a while. Then return everything to normal.

    Thanks again, Nick
  • Intplm.Intplm. Posts: 684Member not call for hi heat as you put it. !!!!! Turn the power off. !!!!! Wait about five minutes. Not any less then five minutes. You need to purge with the power switched OFF to the boiler.

    You don't mention that you are opening the zone valve
    manually. You need to open the zone valve manually on the zone you are trying to purge.

    Think of it this want to make a complete circle of water through the zone, pushing the air out along the way.
    It takes more time then you have been describing.

    The other things you are doing seem to be correct as far as I can tell from here.......

    Another thing. You have a air scoop pictured on the system.
    If the air problems persist , you should replace that air scoop with a micro bubble air separator. It is installed wrong and even if it was installed correctly they don't do that great of a job removing air. Micro bubble air separators will remove the air with much less purging and help to eliminate air that might find it's way into the system as has happened here.

  • HVACNUTHVACNUT Posts: 2,041Member
    You might have a bad zone valve. Even manual open, the ball inside could be jammed or the heater is cooked, depending on what model zone valve.
    By the way, what model zone valve?
    What's the pressure on the boiler?
    The air eliminator on top of the green air scoop looks like it needs replacing.
  • Intplm.Intplm. Posts: 684Member
    Agreed with @HVACNUT . But Get the zone purged first. After that we should look to the zone valve and the hi-top above the air scoop. That is probably a reason for the entrance of the air.
  • phnickphnick Posts: 15Member
    Hi guys, appreciate your help so much. The pressure is at 16psi and the valve is a Honeywell f1. Yeah, the air things are old and shot, so I do need to replace those for sure. Someone told me I had to drain entire unit to do that, so I was going to eat and have boiler serviced in the fall and include replacing those.

    Ok, so I am going to try and long purge with unit off. Everything will be closed except bad zone valve (on Manual) and I guess I want the bad zone return open as well, I have been closing it.
  • Intplm.Intplm. Posts: 684Member
    Good. From what you have been doing, adding opening the zone valve should work.......provided nothing else is wrong.
    Do post your results. You are on the right tack.
  • phnickphnick Posts: 15Member
    Dang! Purged for 20 minutes at least. Boiler was off. Turned everything on, boiler heated up, but bad zone gets warm, not hot.

    Attached is a pic of the zone valve. This is while heat is on, and you can see it’s mostly closed. I may be nearing the limits of DIY!
  • Intplm.Intplm. Posts: 684Member
    Ok... Well I think you might be right about that. Time to "punt"!
    Try pushing the lever to See if that heats the zone.
    Also check for loose wires.
  • Intplm.Intplm. Posts: 684Member
    @phnick. If the connections are good, then push the lever to open. If you get heat then you can try replacing the head. The valve should still be good if you get heat when using the lever.

    Changing the head might not be that difficult. Depends on your DIY confidence.
    Google up the directions and see how you feel about it.
  • edited March 2
    If it is the head, replacing it is pretty easy unless it's an older one in which case I recommend replacing the whole assembly. It's just 2 screws and making the wiring connections.
    Often wrong, never in doubt.

    Click here to learn more about this contractor.
  • phnickphnick Posts: 15Member
    Thanks so much, leaving the valve open on manual gets it hot, but it never gets hot enough to heat room to temp. It’s odd, it definitely is hot to the touch, but after a long time it hasn’t heated the room much.
  • Intplm.Intplm. Posts: 684Member
    Time o call in a pro. Best of luck. You have done plenty of the trouble shooting to tell the tech when you have them over.
  • HVACNUTHVACNUT Posts: 2,041Member
    edited March 3
    With the zone valve manually open, does the return pipe for that zone get hot?
    Depending on outside and indoor temps ot might take a while to heat.
  • phnickphnick Posts: 15Member
    Thank you very much folks, especially @Intplm. for sticking with me.
  • HVACNUTHVACNUT Posts: 2,041Member
    Dont leave us hanging man!
    Is she working?
  • phnickphnick Posts: 15Member
    No, same result. When I leave the zone valve on manual the pipes get hot, including the return pipe but it never gets hot enough to heat the room, it’s odd, just not getting full force. The pressure is fine and the boiler temp is at 200.
  • Intplm.Intplm. Posts: 684Member
    @phnick. Let us know what's happening.
  • phnickphnick Posts: 15Member
    Interesting development. I tried it again, and notice the lever on the zone valve was loose, no tension from the spring. But then as it called for heat it opened all the way by itself and the notch hit the little white engage button in the valve. See attached pic. After 5 minutes it closed itself again for no reason, wasn’t to temp. But when I tried to pull lever all the way to manual, even the furthest setting wasn’t enough to hit white engage button??
  • HVACNUTHVACNUT Posts: 2,041Member
    That room might need more cycles per hour than the other zones. If the faulty zone valve is not making the end switch then the circ wont run for that zone. The faulty zone will only heat when another zone is running.
    A box store should have a complete 3/4 Honeywell zone valve. Its 2 screws to replace the actuator. Lock it manual open first. If it's the insert then you'll have to drop the pressure on the boiler to replace it and purge the air again. The insert is held in with 4- 5/16" nuts. Use the new O-ring. Keep it and the brass dry to seat properly.
  • Intplm.Intplm. Posts: 684Member
    @HVACNUT gives great advice.
    @phnick You can probably get it done

    @phnick , based on what you have done And know so far you could change the head on that valve.
    Depends on your DIY comfort level.
  • phnickphnick Posts: 15Member
    I don’t think I have the DIY skills to do that! Is it just the motor replacement or do I need an entire assembly. It seems so odd that it hits the end switch when it’s engaged for a few minutes, but not when it’s manually opened.
  • Intplm.Intplm. Posts: 684Member
    Your decision to do it yourself. Look up the installation instructions. Then see if you want to tackle it yourself.
  • phnickphnick Posts: 15Member
    Thank you! I was looking up instructions. It looks like I can fairly easily slip on a new box, what I am unsure about is if I need to replace insert (inside pipe), that I could not do. Is the only way to tell if I replace box and it still doesn’t work?
  • phnickphnick Posts: 15Member
    Hey folks, I bought a new thermostat just to make absolute certain that was not the issue. It wasn’t.

    I didn’t get a new zone valve because they were out of them at my local store. The thing with it is it seems to function fine, so I am not sure that’s the issue. It runs for about 5 minutes, the lever engages the end switch, then there is a clicking noise and the lever swings closed. Again, this is about 5 min in, and the pipes are hot, just not enough circulation to heat room.

    Anything else I can try?
  • phnickphnick Posts: 15Member
    Just an update, all fixed. I bought a new zone valve. I didn't need to replace the plate for the actual valve in the pipe, I just need the new box (motor/gears)... plugged that in and it worked fine.

    Thank you again for your help, Nick

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