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Upstairs Baseboard Heating hotter than thermostat is set.

Mike5565 Member Posts: 4
Not sure if in the right category my apologies if I am. So a little back story. Two weeks ago the upstairs zone had a leak in one of the baseboards, one of the pex crimp connectors snapped. I re-crimped the pipe, but had a lot of water leak before I realized we had the leak. Now I am nothing industry wise, but I am a fairly hands-on individual so I just assumed leak gone and system should be back to normal. However the upstairs zone that had the leak now heats the house to 85 degrees when thermostat is set for 70 degrees. I am thinking maybe coincidence and just broken thermostat, but figured maybe it could be something else before I swap it. Thank you for any insight.


  • mattmia2
    mattmia2 Member Posts: 8,874
    Did you manually open any zone valves or flow checks when you bled the air out of it after you fixed the leak? Did you close any valves to purge it?
  • Mike5565
    Mike5565 Member Posts: 4
    Honestly just fixed the leak and that was it? Is there a bleeder screw by the furnace or is it located on the baseboard heaters?
  • Jamie Hall
    Jamie Hall Member Posts: 22,162
    There's a good bit more to restoring a hot water system after fixing a leak. There will be a bleeder screw on the baseboards, but you may also need to bring the system back up to pressure -- and you may need to purge air from the system, rather than just bleeding it.

    However... I'm really puzzled. Normally when a zone needs bleeding, it can't produce the needed heat. In this case, it would appear that the zone which needs bleeding now overheats radically. Can you clarify? The thermostat which is being used contols the zone which was worked on, and it is that zone and only that zone which is now overheating?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Mike5565
    Mike5565 Member Posts: 4
    so only two zones in the house it’s just a town home. So it is the upstairs zone that experienced the leak and is also heating beyond what the thermostat is set at. After I fixed the leak and heat never stopped working I figured I was good. Is bleeding the zone similar to bleeding brakes?
  • Jamie Hall
    Jamie Hall Member Posts: 22,162
    Not realy -- particularly with baseboards. Which is not to say you might not get lucky. You need to have the system pressure correct. Then hustle upstairs and open the bleeder; let it go until only water comes out. Then hustle back downstairs and check the system pressure and, if necessary, bring back up to where it should be cold (if you have an autofeeder, that should have taken care of that).

    The problem is that air bubbles may be trapped elsewhere in the baseboard or the piping leading to it -- unlike bleeding brakes, where the lines are so small that that is unlikely (if you do it right...). If there's enough trapped air, it can impede circulation, and it will be necessary to run water through the system much faster --this is called purging. If the system is heating properly, though, you may not have to do that.


    Overheating is not operating properly. On the other hand, it's very unlikely that excess air will cause overheating, since it reduces flow. So... Is the thermostat turning off but the radiators continue to heat? If the thermostat is off, is the zone valve closed (or zone pump off)? If not, why not?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • bburd
    bburd Member Posts: 784
    edited February 2022
    There could be a short in the thermostat or its wiring, but the thermostat probably has nothing to do with this.

    If the circulator shuts off when the thermostat shuts off but the radiators stay hot, most likely you are getting gravity flow because the flow check or zone valve was opened manually and not returned to its normal automatic position, or is defective and not closing as it should when the zone thermostat is satisfied.

    It’s not a bleeding problem; that would cause a lack of heat, not too much.

  • Mike5565
    Mike5565 Member Posts: 4
    edited February 2022
    So here’s a few pictures not sure if they help any. YouTubed bleeding the baseboards and have to move out 2 dressers trying to find a bleeder screw still, but here’s some pictures of it helps.
    JUGHNE Member Posts: 10,909
    If your pressure gauge is correct, you are close to 30 PSI, when the relief valve should open.
    Scotty to Kirk: "Captain, if we push her any more she will blow"!

    So your relief valve may start to dribble out at 30 PSI.

    I wonder....long shot....if this zone was always running somewhat, but hindered by air in that piping.
    You get a leak, the air leaks out, and then the water leaks and this you notice.

    You fix the leak and refill that zone. Lucky you, there is no air blocking flow upstairs any more and it over heats.

    You have 2 zone valves for heating and I am guessing the 3rd is for the hot water tank.

    Zone valves stop the flow of heated hot water thru them.
    But the return side of the heater circuit can experience phantom/ghost just by gravity up to the 2nd floor.

    There usually are "flow checks'' which close to prevent this and only open with pressure applied from the pump thru the open zone valve.

    Also, if those are Honeywell valves they have a lever on the bottom to manually open that valve. Although they usually revert to normal after power is applied calling for heat.

    You have a tstat for each floor??

    Show the boiler piping from 90 degrees of the picture you have, go to the left side of the boiler so as to view separate pipes without over lay of adjacent pipes.
    EBEBRATT-Ed Member Posts: 14,543
    Looks like 3 zone valves 2 for the house and 1 for an indirect. Maybe the zone valve is stuck open
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 6,753
    Being a hands on homeowner, you may have not used a pro to do needed maintenance on this equipment. There are 2 things that scare me about this.

    1. The pressure gauge (if accurate) is at 30 PSI and there is no water on the floor. This could be a "failed stuck closed" relief valve. if that is the case, you should stop using that boiler immediately!!!
    2. Oil burners need annual maintenance that includes proper burner adjustment with a combustion analyzer.

    Reasons for the problem you know about:
    1. Zone valve stuck open (the silver boxes on the copper pipes) see if the small "Auto/Manual" lever tab near where the red as yellow wires come out of the silver box is in the Manual position.
    2. Wires have loose of missing insulation forming a cross connection (sometimes incorrectly called a short circuit) completing the circuit to the zone valve even when the thermostat is satisfied
    3. Zone valve is defective and not closing completely when the thermostat is satisfied.
    4. there are several other possible causes but those are the most common.

    Problems you don't know you have.
    1. Auto feed valve (pressure reducing valve) connected on the wrong side of the circulator. This will cause the system to over pressure.
    2. Possible expansion tank failure
    3. Possible relief valve failure
    4. I would like to see a fir-o-matic fuel valve with fusible handle to shut off fuel flow in the event of a fire.

    If you get a pro that knows his stuff, you should get a list of issues that may bite you in the A double scribble. down the road. Some are more urgent than others. Others can wait. And still others may never need fixing. But if you are going to DIY, you should read up on what you are up against. Inside that blue box you call an oil fired boiler... there is a FIRE.

    You are literally playing with fire!

    I hope this helps to get your problems resolved

    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics