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furnace motor

Discussion in 'Electronic Repair' started by Humbled Survivor, Aug 10, 2013.

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    My furnace blower fan motor has 3 wires for two speeds, so I got this to cut
    in half and put the connector between the breakers and the motor. 18 AWG is
    enough, but if not I'll find out. The motor is 220VAC at 1/3 HP. I have to
    take the motor out once a year to lubricate it, and also to swap out motors
    when they go bad. The last furnace tech set me up with a 1/4 HP motor but
    it burned out. The furnace was designed for 1/3 HP, and I have a backup
    motor when this one goes bad.

    This is a computer plug and socket. I wanted a different kind to give equal
    weight to all 3 connectors and to prevent some whimso from plugging 110 into
    a 220 receptacle.

    Not that it is going to make any difference, but tell me what you think.
  2. Guest

    You got me curious here, where do you live ? Down here the furnace gets 110and the condensing unit gets 220. I have never ever lubed a furnace blowermotor and just assume(d) it was permanently lubed or whatever. I actually have known people who had to replace them from time to time, but never had to myself. On gas furnaces we generally have to replace the ignitors and ifremiss in changing or cleaning filters, overtemp sensors.

    Seems to me unless it is an odd installation you should get at least a decade out of these motors, or is the airway (in or out) somehow compromised, restricted or something ? Of course in some houses there are unavoidable compromises in an installation but I am having a hard time imagining one that would eat blower motors. Even when a forced air is installed in a house that had gravity originally, you might be feeding the system semi-backwards, but the ducts are usually huge.

    Of course some might run the blower all the time, for example if they use it with an electrostatic air cleaner, someone with allergies might do this.

    Anyway, so much for my curiousity. Those PC power cords are not really quite the wire guage I would use for that application. I've seen them someotimes looks like 18 guage or something. In fact I almost have doubt about connecting them to those monster 750 watt PC power supplies, but in reality the PC almoist never could possible draw that. Even a server with dual Xeon (?)processors and 500 GB of RAM shouldn't pull that much, although enough harddrives could add up. That big power outage we had on the east side of the US happened right after I had installed yet ANOTHER 50 pin SCSI drive in mytower, which had two power supplies connected together by the kind of cable in your link. The good old AT days when you could shut off your PC and you knew that lightnoing hitting the power lines would not fry it. Usually.......

    Anyway, if space permits mechanically you can stick like a one horse motor in there, especially when you have 220 V on tap. It will not cost you all that much power unless it is actually loaded. If it is loaded then the problem is obviously that it needs a more powerful motor for the job. I have no idea, maybe your house is 10,000 square feet, but usually in houses that big they install multiple furnaces for several reasons.
  3. cjt

    cjt Guest

  4. cjt

    cjt Guest

  5. bud--

    bud-- Guest

    I know of no requirement in the NEC. The furnace has to be hard-wired to

    A 230V 1/3 HP motor runs at under 4A. It is not the connector I would
    use but should work. Are the cord and connector rated for 230V? If there
    was a fire at the connection it is not likely to go anywhere in a
    furnace (that is, I don't see this as a high risk location).

    I assume the original wiring did not include a ground wire (motor
    grounded through the mounting).
  6. This is an electric furnace in a house trailer. The last 1/4 HP motor
    burned out, so I put in the 1/3 HP motor as designated on the schematic.

    I think I am going to just label all the wires and keep them connected with
    wire nuts. A plug would be nice but it would turn out messy and confusing.
    It's a 1972 house trailer. I've had the furnace apart and put back together
    every which way. I've replaced relays and sequencers, breakers and
    terminals. The furnace guys who come in can't fix it, so I fix it myself.
    It went through last winter without incident. This winter I have a spare
    fan motor/capacitor. The required motor is 240 VAC, 1/3 HP, 2-speed. The
    one in there now I had to reverse the stator so the fan would blow in the
    squirrel cage the right direction.

    Thank you for all of your discussion. It was interesting to read.

    I'm waiting for my buddy to weld the motor mount for the backup welder. Two
    straps of steel wrap around the motor with squirrel cage mounts welded to
    the straps. This required the use of PI to calculate circumference. Two
    large machine screws tighten the straps together. My buddy has a MIG
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