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Please help me rewire garage heater

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fordnutjm
fordnutjm Member Posts: 5
I bought a used Dayton hanging garage heater. I think it's a 3ug73 it was wired with a plug for 110 but I think it should be a 220. How do I change it to run on a 220 ?

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  • Zman
    Zman Member Posts: 7,607
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    It may have come with a 110 plug but I don't think it ran like that.
    Just wire the 2 hots to L1 and L2 and the ground to the green screw and let it rip.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,849
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    I blew the wiring diagram up to read it but it didn't help much. It looks like that diagram covers multiple heaters, some are 208 volt, some are 240 volt.

    There should be a nameplate on the heater which should have the voltage on it. If your using it in your house it should be 240 volt.

    The only information on the diagram is for changing wire so you can run the heater at full output (higher wattage) or lower input (lower wattage)

    If the name plate is 240 volt you should be ok. If not then there could be issues

    Look for more information on the heater or other paperwork
  • HVACNUT
    HVACNUT Member Posts: 5,894
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    Agree with ☝️those guys.
    I will add that you should leave extra length on your incoming feed. Or strip the Romex insulation back. Make nice loops and 90° bends for aesthetics. And wrap the White wire with Red electrical tape there and anywhere there's a junction box or splice, i.e. the panel and thermostat.
  • fordnutjm
    fordnutjm Member Posts: 5
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    Ok, so the 2 hots to L1 and L2 and nothing else has to be changed ?
  • Zman
    Zman Member Posts: 7,607
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    I would double check the voltage rating on the fan if possible. On an unknown heater like that you want to be sure someone has not done an unusual conversion.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • pecmsg
    pecmsg Member Posts: 4,968
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    Have you tested anything with a Meter?

    Just because the plug is a 110 style doesn't mean anything.

    Agree with @Zman Check that motor rating!
  • fordnutjm
    fordnutjm Member Posts: 5
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    That's what I was wondering, how to check it
  • pecmsg
    pecmsg Member Posts: 4,968
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    Look at the tag?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,849
    edited January 2020
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    Should be a nameplate on the heater itself and a tag on the motor. Some equipment is dual rated 208/240 volt. Make sure the heater is grounded and as the correct size circuit breaker.

    Question, how do you know the heater was used on 120 volt, by looking at the plug?? Or were you looking at the white wire feeding the panel? The wire color means nothing....don't trust that to be your indicator.

    You don't want to start a fire or have a dangerous condition. Need to check everything
  • mattmia2
    mattmia2 Member Posts: 9,981
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    That label is for only a single unit. If you put 240v across the resistor you get the outputs in the first half of the table depending on which elements you power. If you put 208 v across it you get the wattages in the second half of the table.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,849
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    @mattmia2
    I thought that too the first time I looked at it, but I did the math wrong.

    Your right, it lists a few different size heating elements all of them can be used on 240 or 208 volts. Obviously the heat output changes with with the voltage change drop from 240 to 208 the heat output drops to 75%.

    I am sure the fan motor is 208/240 rated.

    The op wast saying it had a 120 volt plug??
  • fordnutjm
    fordnutjm Member Posts: 5
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    Yes it has a 120 volt plug. The guy I bought it from plugged it into a regular outlet and showed me that it worked but it just didn't put out much and the fan moves very slow
  • Zman
    Zman Member Posts: 7,607
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    fordnutjm said:

    Yes it has a 120 volt plug. The guy I bought it from plugged it into a regular outlet and showed me that it worked but it just didn't put out much and the fan moves very slow

    That is fairly normal for a 240 volt fan wired to 120 volts. As long as he did not cook the motor, you should be able to wire it correctly and be good to go.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • mattmia2
    mattmia2 Member Posts: 9,981
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    If it is just a shaded pole motor it should run basically like it was on a speed control if you connect it to 120v. If it is an induction motor it could have cooked something.
  • fordnutjm
    fordnutjm Member Posts: 5
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    Ok, I guess I'll just try it on 240 and hope everything else is still wired correct.
  • HVACNUT
    HVACNUT Member Posts: 5,894
    edited January 2020
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    Go get yourself a $30 electric meter and check. You're really only interested in the Watts you need to heat the garage at whatever input voltage is there. You might want to adjust higher or lower.

    The other meatball probably wired 220v to a 120v plug and receptacle because he also (allegedly) married his sister.

    There is a note stating to use #10 AWG regardless, in case you want to change wattage.

    Now the problem is, we know the wire gauge can handle any load, but max fuse sizes range from 15 to 30 amps. What size breaker do you need?
    You dont know.

    Are you going to hard wire it or plug it in?
    Is there an emergency switch if the panel is not nearby. I would put one in anyway.

    What's the operating control? I see a thermostat in the diagram. What is it, a dial?

    And finally, a $30 meter won't do it because once the heater is wired to code and started, you need to check the amp draw and limit, just because who knows who's hands were in there.

    The moral of my story is by you saying "Ok, I guess I'll just try it on 240 and hope everything else is still wired correct." , scares me just a little.
    Zman