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Modine Propane Heater Tripping Breaker

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ktccapo
ktccapo Member Posts: 38
in Gas Heating

Good morning all,

I've got an older (2005) Modine propane heater with its original Fasco blower motor suspended from the ceiling in a commercial warehouse space, direct-vented through the exterior wall.

It's run flawlessly over the years with basic tune-ups.

Recently, we needed to shut off the gas in order to move a wall and relocate the gas line.

After turning the gas back on, and bumping up the T-stat to call for heat, the Modine attempted to fire as per usual, but then tripped the breaker supplying it power. Three subsequent attempts to fire all tripped the breaker as well.

Afterwards, I went up on a ladder, looked at the wiring, didn't see anything chaffed, abnormal, disconnected, etc.

Could it be the blower motor?

Any and all suggestions and advice wold be much appreciated.

Many thanks and best,

KTC

Comments

  • Ironman
    Ironman Member Posts: 7,903
    edited March 16

    Guessing is not diagnosing.

    You’re gonna have to isolate one component at a time until you find the culprit. Using a DMM would be the best approach.
    I don’t believe in coincidences. The fact that a wall was moved right before the problem showed up is suspicious.

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • mattmia2
    mattmia2 Member Posts: 16,624

    of course that thing could be they hit it with something and the ignitor is now shorted

  • pecmsg
    pecmsg Member Posts: 7,036

    Could it be……….Yes.

    It could also be several other things.

    Break out your meter and start troubleshooting

    mattmia2Ironman
  • ktccapo
    ktccapo Member Posts: 38

    Thanks for the quick replies. I can run a meter. Does anyone mind sharing the process I should follow? Exhaust fan, blower fan, igniter, limit switch…where and how do I start?

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 20,136

    Shut off the power and disconnect it from the heater. Then turn the power on and (carefully chek the power. Hot to ground s/b 120 volt

    Hot to neutral s/b 120 volt

    Neutral to ground s/b 0 or very close to it.

    Then shut the power off and use the ohm meter to check the components to ground.

    That is a start.

    Did the wiring that powers this unit run through or near the wall that was taken down?

    mattmia2
  • mattmia2
    mattmia2 Member Posts: 16,624
    https://forum.heatinghelp.com/discussion/comment/1891831#Comment_1891831

    where this gets complicates is if there is a control board that controls the ignition and blower all in one.

    another option is to start unplugging things until it stops tripping the breaker though i don't particularly like this method because it is hard on various electrical components.

  • ratio
    ratio Member Posts: 4,229

    There's only a few line-voltage things on that, the xfrmr that feeds the control board (might be integrated on the board), the blower motor, & the relay that controls the blower (might be integrated as well). The blower motor is a good choice for the first thing to look at.

    Did it get to the point where it lit off, or was it pretty much immediately after the thermostat called for heat (within a second or so)?

  • mattmia2
    mattmia2 Member Posts: 16,624
    https://forum.heatinghelp.com/discussion/comment/1891837#Comment_1891837

    is the igniter also 120v?

  • Jamie Hall
    Jamie Hall Member Posts: 27,304

    I think someone asked, but better ask again maybe. Did the electrical power line get moved? You mention moving the gas line…

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ratio
    ratio Member Posts: 4,229
    https://forum.heatinghelp.com/discussion/comment/1891840#Comment_1891840

    Ah, could be, forgot about that. I'd still start with the blower. Check for ohms line to line, and line to ground. Should be some resistance line to line, and infinite from line to ground.

  • ktccapo
    ktccapo Member Posts: 38

    Evening, thanks again for all the follow-up advice…

    To answer a couple of questions posed:

    1. the unit didn't fire off before it tripped the breaker; it tried to, then the breaker tripped…trying to reset the breaker manually just caused it to trip again; it wold only reset after I switched off the emergency power cut off on the unit.
    2. the wiring for/to the unit was moved, but reconnected in the same manner as previous; armored bx cable, extended and spliced back together in a new junction box…
  • Ironman
    Ironman Member Posts: 7,903

    ^^ ^^
    This is where you need to begin checking. The problem began from the same time that the wiring was changed.

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    HVACNUT
  • 109A_5
    109A_5 Member Posts: 3,946
    edited 8:37AM

    You did not provide the model number, so I am just going with this as an example (PDP150). Looks like most everything is off until the thermostat calls for heat. Then everything is turned on one stage at a time, via the time delay relay and the pressure switch. Do both motors spin freely ? Does the Power Exhauster motor spin up ? Close observation of what stage the breaker trips at will probably lead you to the issue.

    Its probably a motor issue (or possibly a wiring issue depending on what was touched), the 24 VAC transformer may let the smoke out before it ever trips a circuit breaker. And since the thermostat works, probably not the transformer and / or devices powered by the transformer.

    image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • HVACNUT
    HVACNUT Member Posts: 7,423

    A 2 wire switch leg, the white wire might be spliced with neutrals somewhere else?

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