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    gorbengt's Avatar
    gorbengt Posts: 4, Reputation: 1
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    #1

    Oct 5, 2011, 09:31 AM
    Line voltage thermostat wiring: replace single pole with double pole
    Greetings,

    Current setup: Three small rooms, each with its own 120 volt baseboard electric heat, each with a 25 year old wall mount single pole, line voltage thermostat. All 3 room heaters are on the same breaker. Current single pole thermostat connections have 3 wires: black, red and white.

    I need to replace with double pole thermostats so I can selectively turn off individual room heaters.

    I purchased 3 new Cadet (Honeywell) line thermostats, T410B Bimetal 22amp Double Post Wall. They have (2) black and (2) red connections... Labelled L1, L2, T1 and T2.

    I plan to:

    (1) disconnect power
    (2) remove old thermostat
    (3) reconnect power
    (4) determine which wire to thermostat is the hot feed
    (5) disconnect power
    (6) wirenut L1, L2 and hot feed together
    (7) wirenut T1, T2 and load wire together
    (8) Terminate white wire.

    Is this correct?

    Thanks!
    gorbengt's Avatar
    gorbengt Posts: 4, Reputation: 1
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    #2

    Oct 5, 2011, 12:17 PM
    I now believe I understand the correct serial solution is:

    (1) Connect the hot line feed wire to L1.
    (2) Connect/jumper T1 to L2.
    (3) Connect the heater load wire to T2.

    Does this sound correct?

    Also, What about the white wire? I assume that the black and red wires are line and load.

    Thanks!
    tkrussell's Avatar
    tkrussell Posts: 9,659, Reputation: 725
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    #3

    Oct 5, 2011, 01:07 PM
    You need to be very careful using a 2 pole stat in place of a single pole. Only one side is thermostatically controlled, the other is only a switch.

    According to the wiring diagram that should be with the unit, you need to connect line to L1 and load to T1.

    No jumper is needed.

    Cap each L2 and T2 separately.

    http://www.cadetco.com/support/ownersguides/1017.pdf
    jerro's Avatar
    jerro Posts: 172, Reputation: 5
    Junior Member
     
    #4

    Oct 6, 2011, 08:30 PM
    Why do you have to replace single pole thermostat with double pole thermostat since they are 120v heaters?
    gorbengt's Avatar
    gorbengt Posts: 4, Reputation: 1
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    #5

    Oct 7, 2011, 07:58 AM
    I need the ability to turn off individual heaters. The 3 room heaters are on the same breaker, and I only want to heat one room during majority of winter.

    Does the OFF setting on a double pole stat open both sides/contacts, or just the one?
    tkrussell's Avatar
    tkrussell Posts: 9,659, Reputation: 725
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    #6

    Oct 8, 2011, 05:24 AM
    According to the instructions I provided for your stat:

    Note #4- THERMALLY ACTIVATED—BREAKS ON TEMPERATURE
    RISE. MAKES ON TEMPERATURE FALL.

    Which means the other pole opens in the off position, and this pole will close when the temp falls.

    You really should be using a single pole stat for 120 volt circuit.
    gorbengt's Avatar
    gorbengt Posts: 4, Reputation: 1
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    #7

    Oct 8, 2011, 07:02 AM
    Thank you everyone for your help. I was hoping that the Off setting might cut both sides of the 2-pole stat. I must have an Off setting in addition to the thermostatically controlled. During the winter the single pole stat at its lowest setting still uses too much power... so I will wire the two pole stat's 2 switches in serial.
    Titanite77's Avatar
    Titanite77 Posts: 1, Reputation: 1
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    #8

    Nov 18, 2011, 03:49 PM
    If you use the switched side of your dual pole thermostat to control continuity only for the white (neutral) wire and the thermostatically controlled switch for the hot side, the dual pole switch will work just fine and be safe.

    SO, to start, disconnect your dual pole thermostat and put a continuity tester on the leads with the thermostat on but not calling for heat. (you can typically tell this by when it emits an audible click) The leads that light up (or have continuity through them) should be connected to the white (neutral) wire coming from the circuit board and the white wire to your heater. When the thermostat is on, it will only be providing continuity to the neutral leg of the circuit. It will not consume any power or provide any to the appliance.

    The remaining two wires should go to the black wire from the circuit board and the black wire of your heater.

    There must be power present in the black wire to activate the thermostatically controlled switch in the thermostat. So even when you turn the thermostat all the way up to call for heat - there will be no continuity between the latter two wires until power is present.

    For appliances "upstream" of this, simply wire the hot leads and neutral leads in parallel to the next 2 pole thermostat and repeat the above.

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