# Replacing old Honeywell thermostat with new Honeywell thermostat



## thehvacguy (Oct 30, 2009)

See on your new thermostat there are letters on the terminals? On the old thermostat are there letters next to where the wires are? The reason i ask is because the wiring is different for gas heat, and heat pump. The new thermostat is compatable with both. Can you take a look at your furnace? What is the model number? Do you have cooling as well?


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## thehvacguy (Oct 30, 2009)

We need to know what kind of system you have. The wiring is different between gas heat and heat pump, so we need to check the model number. Dont worry, your new thermostat is compatable with both. Can you see letters on the old thermostat where the wires are connected?


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## thehvacguy (Oct 30, 2009)

thehvacguy said:


> We need to know what kind of system you have. The wiring is different between gas heat and heat pump, so we need to check the model number. Dont worry, your new thermostat is compatable with both. Can you see letters on the old thermostat where the wires are connected?


Dam computer


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## 3 legged dog (Dec 21, 2009)

Looks like a line voltage chiller stat. You cant use a 24 volt stat.

here is a link.


http://s3.pexsupply.com/manuals/1253196590775/17427_PROD_FILE.pdf


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## optimizer (Apr 13, 2011)

Thanks for getting back to me! I put together the attached diagram to show the wiring and what the back of the old thermostat looks like. Not many of the wires are labelled but I also added labels for what the switches do.

In the bottom right corner in the square is the diagram that is illustrated on the back panel of the thermostat.

Sorry, not sure what kind of heat system my building has!!


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## optimizer (Apr 13, 2011)

I initially tried uploading the wiring diagram as a PDF, but that didn't work. Here it is in JPG.


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## beenthere (Oct 11, 2008)

Your current thermostat is a line voltage thermostat that is used to control a water valve and the fan motor.

The RTH thermostat you have is a low voltage thermostat, and can not be used on your system, without adding a relay system.


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## optimizer (Apr 13, 2011)

I can return the new one I bought... Is there another model you could reccommend to me?


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## beenthere (Oct 11, 2008)

As far as I know. They don't make a line voltage thermostat that is programmable or digital for your application.


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## optimizer (Apr 13, 2011)

Hi - would something like this work?

http://www.honeywell-thermostat.com/honeywell/TL8230A1003-thermostat.html


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## beenthere (Oct 11, 2008)

It can open the water valve for heating, and turn on the fan to one fixed fan speed. It can't control cooling though.


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## optimizer (Apr 13, 2011)

You mentioned a relay option... is this something common / straightforward / recommended? How would I get more info on getting this done, and/or who would be the right tradesperson (electrician or hvac)?

Thx!!


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## beenthere (Oct 11, 2008)

HVAC would be the right person. its not something commonly done though. So you would need someone that is good with controls and control wiring.


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