Can I use one thermostat?

Discussion in 'HVAC Heating & Cooling' started by fazy, Nov 8, 2008.

  1. fazy

    fazy New Member

    Messages:
    5
    Hello and thanks in advance for any response. I just wired in two 6' 240v 1500w baseboard heaters using 12/2 w grd. in a 10x20 room with 12' vaulted cielings. This room also has very large windows (2 - 6'x6's, a large entry door and two smaller windows) so,... as you can guess, I don't think these two heaters are enough to heat the room in real cold temps. I think if I add two more 4' heaters, it would probably be adequate. I know these two new heaters need to be on a seperate circuit from the 6 footers, but is there any way to have all the heaters on 1 stat?, or do the 2-4 footers need to be on thier own stat? Or, should I re-wire everything with 10/2 so everything could be on the same circuit and same stat? Also, is there a way to use a low voltage stat for these baseboard heaters or do you have to use line voltage stats? Sorry for all the questions... Thanks for your help!
    Last edited: Nov 8, 2008
  2. jimbo

    jimbo Plumber

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    8,997
    Location:
    San Diego
    You have some issues here. Most line voltage stats are rated at 22 amps max. I assume this is all 240 volt stuff, so that would be 5280 watts max. It also means 10 guage wire.

    You answered your question when you mentioned the separate circuit for the new heaters.....no way to have on stat controlling heaters on two different breakers.
  3. nhmaster

    nhmaster Master Plumber

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    3,189
    Location:
    S. Maine
    Yes, you need a relay rated for the combined amperage. They are available at an electrical supply outlet. All the baseboard wires to the line voltage side and a low voltage thermostat will pull the relay in.
  4. hj

    hj Moderator & Master Plumber Staff Member

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    heaters

    I doubt that you would find a 30 amp DPST thermostat, so you would need a relay, which would normally use a low voltage thermostat, but could be line voltage depending on the relay. It would have to be installed in the main wire feeding the heaters because trying to wire the four individual feeds to a relay would create an interesting problem. But then you run into the problem of a 30 amp breaker protecting a bunch of #12 wires, which it cannot do.
  5. fazy

    fazy New Member

    Messages:
    5
    Would this work?

    Could I have two seperate 20A circuits, 2 heaters per circuit (which would be no more that 12.5 amps) to keep within the range, and install 2 seperate relays, 1 controlling each circuit to the heaters, controlled by 1 low voltage stat? Or can 1 stat control two relays? I would think this would be O.K., being that it would then be controlled by low voltage and the circuits would still be well within thier amperage range. What do ya think?:)
  6. jimbo

    jimbo Plumber

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    8,997
    Location:
    San Diego
    I think you are making this too hard. One stat can control 2 heaters. Since you will have separate circuits , why not just put two stats up. I don't think you would have any big problem with balancing the temp if you had the stats in the right place.
  7. Chris75

    Chris75 Electrician

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    608
    Location:
    Litchfield, CT
    Basic rule of thumb is 10 watts per sq. ft. with 8' ceilings, I personally would just install a low voltage tstat with a heat relay.
  8. Chris75

    Chris75 Electrician

    Messages:
    608
    Location:
    Litchfield, CT
    Why would you want two stats on the wall when you can just have 1?
  9. Chris75

    Chris75 Electrician

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    608
    Location:
    Litchfield, CT
    They make 2 circuit heat relays, so 1 low voltage t-stat will control two separate circuits of heat.
  10. Thatguy

    Thatguy Homeowner

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    1,460
    Location:
    MD
    Maybe this was already said, but one T'stat controls the coils of two relays and each heater is controlled by the contacts of each relay. The relay coils can be powered by 24vac or higher voltage.
    :confused:
  11. fazy

    fazy New Member

    Messages:
    5
    I agree with Chris75 on this one. I would much rather have just 1 stat on the wall to control everything. It's not that I'm trying to make this hard...because it's really not, I just want to make it right. Thanks!:)
  12. fazy

    fazy New Member

    Messages:
    5
    Chris75...are these 2 circuit relays something that can be bought at Lowes or is this a specialty item?
  13. Chris75

    Chris75 Electrician

    Messages:
    608
    Location:
    Litchfield, CT
    I've never seen them at lowes, I would just go to a local electrical supply house.

    Here is the model # I use,

    24A01G3 25A/240v this comes with a built in transformer for the t-stat, and will control (2) 6000w loads. they cost around 90 bucks.


    http://www.chathambrass.com/Pages/ProductCategories/11Relays.htm
    Last edited: Nov 9, 2008
  14. fazy

    fazy New Member

    Messages:
    5
    Thanks a million! Your help is very much appreciated!:D
  15. nhmaster

    nhmaster Master Plumber

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    3,189
    Location:
    S. Maine
    Didn't I already say all that way back at the beginning? :rolleyes:
  16. Chris75

    Chris75 Electrician

    Messages:
    608
    Location:
    Litchfield, CT
    Yep, but everyone ignored you. :D
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