Heater Problems!

Discussion in 'The Garage' started by P B G, Nov 3, 2012.

  1. P B G

    P B G Long timer

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    Talk to me HVAC guys.

    I have a Modine 100000 BTU heater, ductless in my shop.

    The standing pilot won't stay lit. Getting 27.2 millivolt at the thermocouple when I hold the red button in and relight my heater.

    Getting ~28 volts at the gas valve when I turn the thermostat up, thus indicating the safety switches are not tripped (they are in series with the gas valve on the wiring diagram).

    What else is there that could be bad? I tried a new thermocouple for 11$ sh1tz and giggles, no go, which I suspected would be the case with the reading I got.

    I don't want to spend a couple hundred on a gas valve if I do not have to, but what else could it be?
    #1
  2. dtysdalx2

    dtysdalx2 PITA but useful

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    I'd probably put up model number and how old it is.

    Try a propane torch and get the thermocouple red hot yet? Correct thermocouple? Tried the old one again? Clean it with emery cloth.

    Gas valve issue is next.
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  3. P B G

    P B G Long timer

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    Sure did use a propane torch, that was my first instinct.

    Heater is a Modine PD 100AA0111 - Age is unknown, building is ~30 years old, but unknown who/when it was installed.
    Red hot, pilot lit, release button - gas turns off.

    Voltage at gas valve like that goes well above 30 during propane heating.

    Thermocouple seems correct, it is appropriate for the gas valve mfg. Not a OEM product, but still I think an appropriate thermocouple replacement.

    Swapped back to the original one anyhow, as I think it is a higher quality product, and generates good numbers on the meter.
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  4. dtysdalx2

    dtysdalx2 PITA but useful

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  5. P B G

    P B G Long timer

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  6. dtysdalx2

    dtysdalx2 PITA but useful

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    Man, I hope not. :lol3

    I need more info, like a wiring diagram and specs. Poor connection at the thermocouple/gas valve (the cold end)?
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  7. P B G

    P B G Long timer

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    Connection seems good, it un-threaded smoothly by hand after cracking the threads loose. No signs of corrosion in the area/gunk in the threads, its not a gas connection after all.

    [​IMG]
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  8. dtysdalx2

    dtysdalx2 PITA but useful

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    Gas valve issue. Pilot light should light and stay lit with no power at all (standing pilot I think).

    Model # of the gas valve? Not sure the specs of the mV range for the gas valve.

    Geez, now you made me tear apart my water heater and clean the thermocouple even though it works fine. :)
    #8
  9. P B G

    P B G Long timer

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    That was my understanding of these units as well, if you had the right MV at the thermocouple, that it should stay lit.

    With how stupid expensive gas valves are I may just go away from a standing pilot, which just annoys me during the summer.
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  10. Beezer

    Beezer Long timer

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    a Modine that old prolly has cracks in the heat exchanger anyway. I would spring for a new HotDog before spending too much on repairs for that dinosaur. sorry.... but been there & done that
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  11. dtysdalx2

    dtysdalx2 PITA but useful

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    I use a sunflower propane in my garage. Of course I have a CO detector in the garage also. Never makes it go up.

    If the HE was cracked...:huh

    Gas valves are cheap on flebay.
    #11
  12. jbhawley

    jbhawley WTF- Gus?

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    Hold the pilot button on the valve and propane torch heat up the thermocouple for a few seconds. This fools the valve into thinking the pilot/thermocouple is on. Then turn the valve to on position and torch light the burners. You should hear the gas coming into the main burners. If this happens adn the main burners light up properly, just let it burn until...usually the thermocouple will cool down (since the pilot is not on) and the heater will shut down.

    If you cannot get the heater to light up in the manner then you either have a safety switch tripped or a bad valve.

    Also, check to make sure that when you turn the valve knob from off > pilot > on that the underneath valve is turning and the plastic knob is not stripped/broken and just free spinning. I have seen this happen all too often with old heaters.
    #12
  13. rebake

    rebake Long timer

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    Blow out the pilot assembly with compressed air,the kind used to clean computers.Anything as small as a spider egg can restrict them enough to not work.Valve diaphram could be bad also.Ed
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  14. Bronco638

    Bronco638 Nobody Home

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    +1 on this but it sounds like the gas valve might be bad.
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  15. P B G

    P B G Long timer

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    So my shop has 2 heaters!

    The one referenced in this thread I haven't tried the air yet - but I do think we're dealing with a gas valve issue.

    My second heater is also acting up, I suspect it has an issue with plugging in the gas line, as it has a rather yellow flame, although judging from the rust up under the heater, I think it is the OEM one with the shop.

    So I am almost thinking of installing two new heaters.
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  16. Bronco638

    Bronco638 Nobody Home

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    Have you checked the gas line drip legs at each heater unit? You may have condensation in the gas lines. The yellow flame indicates poor combustion (as you may know).

    I had an issue with my garage heater where the pilot light sounded like someone was blowing on it or it was exposed to a stiff breeze. Occasionally, it would go out. It turned out that the pilot assembly was dirty. As rebake mentioned, a blast of compressed air should resolve that. My yearly maintenance, before I light the heater for the winter, involves liberal applications of compressed air to all of the internals. That's overkill but it does clean a lot of residual dust and has kept the pilot light working, issue free.
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  17. P B G

    P B G Long timer

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    Hey thanks all for the help,

    @Bronco638 - just did that tonight to the sterling heater. Nothing really in the cap.

    This is the second one, which I can keep the thermocouple going by hitting it with propane till red, but then it turns off, so I suspect this was an issue with the pilot venturi. BUT - This one does have a cracked heat exchanger *gasp*.

    SO I think the sterling is prone to replacement.

    The other heater, the Modine is still resisting efforts, it seems like its a gas valve - I'll probably convert the modine to intermittant start.

    That said,

    Anyone install radiant natural gas heaters? If I replace the 100000 btu sterling with a radiant, it seems like that would give me one forced air, one radiant, so the air temps could be controlled.

    Anyone knowledgable in radiant gas heaters?
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  18. Bronco638

    Bronco638 Nobody Home

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    I have a flame heater while a neighbor has a radiant unit from the same manufacturer (Vanguard). According to the literature, the open flame unit will heat the air which, in turn, heats objects within the warm air. The radiant unit supposedly heats objects which, in turn heat the air.

    My neighbor doesn't use his much anymore because he finds it to be ineffective. I love mine. However, I have never really compared them, I'm just going on what he's saying.

    How may sq. ft. do you need to warm? Forced air might be the most efficient method. And, definitely replace the unit with the cracked h.e. I don't want to read about you being overcome by c.o., in the Sun-Times. :D

    EDIT: I installed the unit in my garage. Not hard at all. However, if yours is mounted from the ceiling, you'll need some sort of lift. Working on a ladder is a no-no. The piping isn't as hard as you would think. The t-stat wiring should be pretty straight forward.
    #18
  19. P B G

    P B G Long timer

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    Annnnddddd...

    Success.

    So I like to provide conclusions to my threads when I can.

    First heater - Modine is now up and running.

    Problem was the heater valve, replaced unit with an intermittent pilot unit (the type with spark ignition to fire up the pilot to then light the burner.

    Benefit to this route is that 1 - my standing pilot won't blow out. And 2 - I should use less gas yearly than with a standing pilot, and I eliminated an ignition source for when I'm using volatile chemicals..... :freaky



    Second heater is still resistant. Very similar symptoms, but the crack in the Heat Exchanger is troubling. So I may not convert the gas valve on that, but it gives me some time to do research. Almost considering some form of solar - evacuation tubes perhaps to provide day time heating, then I'll still have gas to maintain at night. On separate thermostats I can use gas to maintain minimum night temps, and then set the solar to bring the temps way up... things to consider.
    #19