240v wall thernostat works, but...

Discussion in 'Electrical Forum discussion & Blog' started by Ken Tannenbaum, Oct 28, 2010.

  1. Ken Tannenbaum

    Ken Tannenbaum New Member

    Messages:
    17
    I installed two baseboard heaters running off a 240v bi-pole thermostat and first wired it incorrectly blowing the circuit. The short happened at one of the radiators, not the thermostat. Now it's wired right and works, except that the instructions with the thermostat say it should make a clicking sound when it goes on, which it doesn't do. Is there a chance I damaged the thermostat? And could that be dangerous? Thanks!
  2. hj

    hj Moderator & Master Plumber Staff Member

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    26,539
    Location:
    Cave Creek, Arizona
    Does it work properly? IF so, then you did not damage it, regardless of whether you hear the contacts click or not. If the contacts did NOT open, or close, which creates the "click" the heaters would either not turn on or not turn off.
  3. Ken Tannenbaum

    Ken Tannenbaum New Member

    Messages:
    17
    It's working fine so thanks for the advice....wish I was working!
  4. Thatguy

    Thatguy Homeowner

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    1,459
    Location:
    MD
    Switches are supposed to have a "snap action" so the arc during switching doesn't last too long. They use little magnets and springs to do this.
    I guess it's possible that this t'stat doesn't have this snap action anymore and so it won't last long. Can't say for sure, though.

    One way to check this would be to put an AM radio nearby tuned between stations. Arcs radiate radio waves and a drawn out arc should sound like a crashing sound for a half second or so, rather than just a 'pop' sound.
    Last edited: Oct 28, 2010
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    21,950
    Location:
    New England
    The switch has two poles, but breaking either one will cause the heater to stop working. One of them could be welded closed, and that could prevent the two from snapping back...it would depend on the construction of the switch. Or, it could be working fine. You could find out if that is the case with a meter. With the power off, the connection between one side of the switch and the other should be open on both poles. Or, with the power on, measure from the output of one side to the input of the other (do it both ways). If it is zero, the pole is open, if it reads 240vac, that pole is welded shut.
  6. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    With the contacts closed confirm that you have less than 30 millivolts across those closed contacts with rated current flowing through them.
    More than 100 mV is bad.

    Open contacts should have 240 v across them.
  7. Ken Tannenbaum

    Ken Tannenbaum New Member

    Messages:
    17
    Thanks for the useful tips....I'll get to it this weekend without a doubt.
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