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Old 10-04-2011, 04:21 PM   #1
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thermostat wiring- replacing single pole w/ 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!
- Gordon

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Old 10-04-2011, 04:24 PM   #2
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thermostat wiring- replacing single pole w/ double pole


You only need single pole t-stats for 120 volt heaters.

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Old 10-04-2011, 04:34 PM   #3
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thermostat wiring- replacing single pole w/ double pole


The problem is that the single pole t-stats don't completely turn off, so I have all 3 heaters going when the majority of the time I only want one to function. Two pole provide the off setting I need.
Thanks,
- gordon
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Old 10-04-2011, 11:38 PM   #4
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thermostat wiring- replacing single pole w/ double pole


You can use double-pole thermostats as single pole units.

Most double-pole line voltage thermostats will break only one pole when cycling on and off.

Connecting the poles together in parallel as you planned will not work.

To make them work properly as single pole units, wire the 2 poles in series:

Wire-nut T1 and T2 leads together, and tuck into the box.

Use the remaining L1 and L2 leads to control your heaters.
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Old 10-05-2011, 08:23 AM   #5
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thermostat wiring- replacing single pole w/ double pole


Did you mean
Wire-nut L2 and T2 leads together, and tuck into the box.

Use the remaining L1 and T1 leads to control your heaters.

I can't see how you would have any t-stat output with T1 and T2 wire nutted and in the back of the box.
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Last edited by Jim Port; 10-05-2011 at 08:26 AM.
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Old 10-05-2011, 03:11 PM   #6
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thermostat wiring- replacing single pole w/ double pole


The parallel connection comment took a while to sink in.
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?
What about the white wire?

Thanks!
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Old 10-05-2011, 04:08 PM   #7
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thermostat wiring- replacing single pole w/ double pole


Quote:
Originally Posted by gorbengt View Post
The parallel connection comment took a while to sink in.
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?
What about the white wire?

Thanks!
I have several of these thermostats installed in my house and they are listed for both 120 and 240 operation.
In 120 volt operation L1 and T1 are the only terminals used. Do not use L2, T2 as these only interrupt power when the thermostat is dialed to OFF

For 120 connection, connect incoming hot to L1 and the heater to T1. Wirenut the incoming white neutral to the heater white neutral.
To the OP for educational purposes. 240 line voltage thermostats that have an OFF position on the dial open both contacts when dialed to OFF. When controlling temperature, only one contact is cycled.


Last edited by a7ecorsair; 10-05-2011 at 04:13 PM.
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