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Old 11-27-2009, 08:53 AM   #1
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Thermostat problem


I went to install a programable thermostat in my dads house the other day and came into a problem. He has baseboard heating. So I pulled the thermostat off the wall and looked at the back of it and it was connected with 12/2 wire. So I went to test the voltage thinking that it would be 120 but it was 24 volts.
So I go into the basement to the boiler and the wire coming off the boiler is 18/2 wire and then about 10 feet down the line they splice the 18/2 wire to 12/2 wire.
Its been like this for a long time and he never knew that it was spliced to bigger wire.
So what I was going to do was just splice it again in the box that the thermostat is in to 18/2 wire.
But the problem i was having with that is the old thermostat wires are on the terminals labeled 1 and 2 so I wasnt sure what the would cross reference with the new thermostat.

Any suggestions?
Thanks
-Brian

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Old 11-27-2009, 09:00 AM   #2
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Thermostat problem


What type of t-stat is the new one (as well as the old one). Was the old one for heating only? (two screws) Is the new one a programmable type (multiple screws)

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Old 11-27-2009, 09:05 AM   #3
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Thermostat problem


You should use the "R" and "W" terminals for heating only.
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Old 11-27-2009, 09:43 AM   #4
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Thermostat problem


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Originally Posted by ControlTech View Post
What type of t-stat is the new one (as well as the old one). Was the old one for heating only? (two screws) Is the new one a programmable type (multiple screws)
The old one is an old honeywell with three screws but only two wires connected a black to the number one terminal and a white to the number two terminal. It is just for heating
The new one is a programable type.
The black wire is connected to terminal one and the white wire is connected to terminal two.
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Old 11-27-2009, 09:52 AM   #5
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Thermostat problem


Then just like KBSparky said, the wires get connected to the "R" (typically RED for 24 VAC power feed) and "W" (typically WHITE for heating SWITCHED wire back to the furnace/boiler).

Since it is a programmable type, hopefully it has battery power and isn't relying on constant 24 VAC to run it's scheduled programs. If so, you will need a 24 VAC "common" (usually BLUE) to provide power to the stat itself.

If that is the case, run the neutral/grounded wire from the 24 VAC transformer on the furnace/boiler to the "C" terminal on the stat - but more than likely this isn't the case.
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Old 11-27-2009, 09:57 AM   #6
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Thermostat problem


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Then just like KBSparky said, the wires get connected to the "R" (typically RED for 24 VAC power feed) and "W" (typically WHITE for heating SWITCHED wire back to the furnace/boiler).

Since it is a programmable type, hopefully it has battery power and isn't relying on constant 24 VAC to run it's scheduled programs. If so, you will need a 24 VAC "common" (usually BLUE) to provide power to the stat itself.

If that is the case, run the neutral/grounded wire from the 24 VAC transformer on the furnace/boiler to the "C" terminal on the stat - but more than likely this isn't the case.

Well where its spliced in the basement the red wire from the 18/2 is spliced with the black from the 12/2 and the whites are spliced together.
There is also two AAA batteries in the thermostat. And in the directions for the new t-stat it says not to use the blue wire if there is one.

Thanks for your help
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Old 11-27-2009, 10:03 AM   #7
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Thermostat problem


Oh, OK. Then just connect the wires to the new stat at "R" and "W" - polarity doesn't matter in this case since the stat isn't looking for a power source.

(The relay in the stat will close the contact between "R" and "W" on a call for heat.)
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Old 11-27-2009, 10:07 AM   #8
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Thermostat problem


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Oh, OK. Then just connect the wires to the new stat at "R" and "W" - polarity doesn't matter in this case since the stat isn't looking for a power source.

(The relay in the stat will close the contact between "R" and "W" on a call for heat.)
Thank you very much for your help

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