What would cause a gas furnace to draw too many amps?

Discussion in 'HVAC Heating & Cooling' started by kailor, Dec 23, 2011.

  1. kailor

    kailor New Member

    Messages:
    22
    Location:
    Huntsville, Alabama
    What would cause a gas furnace to draw too many amps?
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Exactly what do you mean by too many amps? As in it blew a fuse??? That is a short circuit, look for burned transformer, overheated motor, etc.
  3. kreemoweet

    kreemoweet Member

    Messages:
    374
    Location:
    Seattle. WA
    Stalled/jammed blower fan motor?
  4. Runs with bison

    Runs with bison Member

    Messages:
    897
    Location:
    Midwest
    Can the blower turn freely? I had a bearing failure in one many years ago, it seized. Interestingly, it didn't trip the breaker, and the blower motor didn't burn out...which was good because I couldn't find replacement bearings and had to rebuild it from parts I scavenged off another similar old blower that a shop had removed when replacing a unit. I think I handed the shop owner a couple of bucks for the old unit, other than that the repair was free.

    Anyway, I'm assuming blower because it is the biggest amp draw. The second biggest user would be the induced draft fan.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,054
    Location:
    Cave Creek, Arizona
    quote; The second biggest user would be the induced draft fan.

    It may be the "second biggest draw", but it still a "Very small" one. We would have to know what he means by "excessive amps" and how he determined it.
  6. kailor

    kailor New Member

    Messages:
    22
    Location:
    Huntsville, Alabama
    Merry Christmas everyone! I'm helping my sister-in-law with this issue. I'll try to find out what the amp draw was according to the repairman. No one available til Tuesday. She said they got the furnace running but did not know how long it would last. Right now, I've very limited information. Thanks for your inputs thus far.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,268
    Location:
    New England
    If the voltage was marginal (say in a brown-out), and things were 'on the edge' of accepability, it could draw excessive current and trip or blow a safety device. When I had my air handler/a-c unit installed, I installed a low-voltage cutout device. I think it was made by IDS. It's about the size of a deck of cards, has some controls on it to set the desired operating range, some LED indicators, and an internal relay to disable operation if the power is outside of parameters you set. No idea if it has saved my system, but it also has a time-out after power outages to prevent operation immediately after power reapplication when it can fluctuate radically for a few moments or so, thus further protecting things while the voltage is all wacky until it stabilizes. The internal motors probably would be okay, but the unit has at least a couple of circuit boards, and not asking them to operate until the power is stable is probably a good thing.
  8. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,450
    Location:
    Houston, TX
    Sounds to me that the service man, was blowing a little smoke. Maybe not.

    It is very disturbing how they take advantage of the unknowing. Maybe he spoke the truth. who am I to judge.


    If she called because of a blown fuse, then Jim's answer makes more sense than mine.


    Have a happy Holiday.
  9. kailor

    kailor New Member

    Messages:
    22
    Location:
    Huntsville, Alabama
    The blower motor was bad.
  10. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    We appreciate that you came back and gave us the outcome. Sounds like the service man knew what was up but just didn't explain it very well. Motors do go bad, and hopefully this did not cost you too much...maybe an arm and just one leg, not both!!!
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