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Hot water coil system blows cool air

I'm in Austin. We got power back on and our gas powered boiler is giving out hot water but our vents have started blowing cool air since early AM (had been blowing hot air just last night). I double checked our Nest thermostat - it's on heat mode and can't catch up. We've turned it off to retain leftover heat. I'm not sure but I looked up the HVAC unit in the bathroom ceiling, it (Firstco HBC-HWQ) looks like it's a hot water heating unit with a fan coil. Could this be hot water not making it to the unit? Something obvious I could triage while I wait for help to arrive, which could be a while?

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 11,987
    Did the pipes freeze while the power was off? If they did you could start with a hair dryer or a heat gun to thaw them out (if metal pipe) If pex be very careful


    And before you start heating make sure you know how to shut the water off to those pipes in case they are split.

    See if you can find the pipes that feed the coil and follow them back to the boiler check for frost/frozen

    Were they blowing hot air after you got the power back on or before?

    Feel bad for everyone down there
    HVACNUTSuperTechMaxMercyitsfreezinintx
  • itsfreezinintx
    itsfreezinintx Member Posts: 4

    Did the pipes freeze while the power was off? If they did you could start with a hair dryer or a heat gun to thaw them out (if metal pipe) If pex be very careful


    And before you start heating make sure you know how to shut the water off to those pipes in case they are split.

    See if you can find the pipes that feed the coil and follow them back to the boiler check for frost/frozen

    Were they blowing hot air after you got the power back on or before?

    Feel bad for everyone down there

    Thanks so much for your response. The heater did blow nice hot air for 24 hours after the power came back on, which helped a lot, and then overnight it transitioned to only cold air. I will try to follow the pipe to it from the water heater and check for frosting there as that is the end that isn't inside the apartment. Will post pictures here
  • mattmia2
    mattmia2 Member Posts: 5,506
    Is that the only source of heat or are there other heat emitters and are they working?
  • itsfreezinintx
    itsfreezinintx Member Posts: 4
    @EBEBRATT-Ed I took another peek into the hydrocoil system. I didn't spot any splits in the pipes. There does appear to be some bluish-green corrosion on the copper pipe that inputs hot water into the hydrocoil system. There is a very slow drip of water from it too. Looking at the black wood underneath, I suspect it was some pre-existing leak due to corrosion. I'm attaching pics for reference Am I missing any obvious sign of frost? Another thought I had was if the water pressure was low, maybe that could prevent the hot water from reaching the hydrocoil system but am not sure if that is how it works. The overall water pressure has gone down a bit and varies a bit due to pipes and even mains bursting all over the city, but it is still seems decent as I took a nice hot shower today.

    I'm also attaching a pic of all the pipes that go out from the top of the boiler, 3 of them have valves, can't quite be sure which one supplies the hydrocoil. Temp is going to be subzero tonight. Do you still recommend I try to shut off any of my valves? I reckon I'll have to figure out which is which even if it is recommended.

    I'm using my oven and steam off hot showers to help heat up the place as stores near me are out of space heaters. It's not too bad. I'm hopeful the warmer weather next week can help while I deal with this with management which is spread too thin. Thanks for all ya'all's responses. I really appreciate it.





  • itsfreezinintx
    itsfreezinintx Member Posts: 4
    Thanks @Youngplumber for your feedback - I will get the copper pipe addressed as well. In a way, I'm glad I took a peek there
  • Jon_blaney
    Jon_blaney Member Posts: 271
    Is your fantcoil connected to a water heater? Did you have water pressure problem?

    You could have air in the system related to low water pressure if it is an AquaTherm system. The installation and application manual can help on how to bleed the system.
    mattmia2
  • mattmia2
    mattmia2 Member Posts: 5,506
    If you lost water pressure completely at some point and air got in to the system, that coil would be the first place it went, if there is a bleeder valve on it, you should open it and see if you get air or water out of it.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 11,987
    @itsfreezinintx

    If this system is a hot water heater as others have mentioned then yes loosing water pressure could have introducec air into the system. Need more pictures of the water heater /boiler.

    Is the fan coil your only source of heat?

    The fact that you got heat out of it last night means it didn't freeze hopefully that is ok. See if you can find the circulating pump for the fan coil and see if that is running. It must have one
  • mattmia2
    mattmia2 Member Posts: 5,506
    I think that Taco box with flex going in to it in the second picture is the junction box for the circulator.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,176
    mattmia2 said:

    I think that Taco box with flex going in to it in the second picture is the junction box for the circulator.

    Correct. that is a Taco Circulator with a relay built-in. The thermostat wires can go directly to the circulator relay, there is also a set of dry contacts to power up the "Burner". They called them Zone Circulators. In your case, the dry contacts may operate the fan since the water heater is maintaining temperature. First Company made a lot of these, I installed one in my own home in the 1980s it used the potable water in the fan coil. Then I read about the problems with stagnant water in the coil over the summer developing micro-organisms (you will never guess what auto-correct just spelled) so I changed it out to a boiler when the water heater failed a few years later.

    The system heated pretty well. As long as the fan is working and the water is hot, the pump is not circulating the hot water thru the coil. Look for the pump not operating (they are very quiet so I use a piece of tubing as a stethoscope) or a blockage in the pipes (air can be the blockage so look for an air vent in the First Co. coil near the top).

    Yours Truly,
    Mr.Ed
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org