(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 7 of 7

Thread: 240v wall thernostat works, but...

  1. #1

    Default 240v wall thernostat works, but...

    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. #2
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    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. #3


    It's working fine so thanks for the advice....wish I was working!

  4. #4
    Homeowner Thatguy's Avatar
    Join Date
    Aug 2008


    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 by Thatguy; 10-28-2010 at 07:07 AM.

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    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.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #6
    Homeowner Thatguy's Avatar
    Join Date
    Aug 2008


    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. #7


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

Similar Threads

  1. Floor warming... 120V mat vs. 240V thermostat
    By Fistor in forum Electrical Forum discussion & Blog
    Replies: 13
    Last Post: 10-15-2009, 02:01 PM
  2. 220/240v from basement to kitchen.
    By Rughead in forum Electrical Forum discussion & Blog
    Replies: 6
    Last Post: 06-03-2009, 06:45 AM
  3. 240v 2 pole grounding switch to receptacle
    By RileyD in forum Electrical Forum discussion & Blog
    Replies: 5
    Last Post: 04-08-2009, 04:36 PM
  4. 240V electric water heater on 120v circuit
    By miscmail1560 in forum Electrical Forum discussion & Blog
    Replies: 26
    Last Post: 12-12-2007, 04:52 PM
  5. 240v single pole?
    By hids2000 in forum Electrical Forum discussion & Blog
    Replies: 16
    Last Post: 08-11-2007, 07:37 AM


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts