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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I am attempting to fit a Honeywell rth7600 thermostat to my

Customer Question

Hi Mark. I am attempting to fit a Honeywell rth7600 thermostat to my Braemar heater. It uses just 2 wires to activate the heater, but not sure where these 2 wires should connect in the new thermostat. Can you advise. Thanks / Rob
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.

Hello, I have not seen Mark around for quite a while.

Please attach a well focused, close up photo of the wiring diagram glued inside the service panel,you can use the paper clip icon at the right end of the toolbar at the top of this dialog box, Include a picture of the thermostat wire connections to the printed circuit board in the same area.

If there is no paper clip icon, look for the '+attach files' link at left of your send button.

I can mark it up with wiring instructions.

Customer: replied 1 year ago.
If I had this I wouldn't be asking the question ........
Expert:  Phil replied 1 year ago.

I see.

We can try another tactic. Send me a photo of the printed circuit board with the thermostat wire connections on it, you will need a multi meter to do a few tests to insure that the thermostat wires connect to a 24 volts, and I will then ask you to do a few tests so that we can determine how to connect the new thermostat, probably with a FAN ON function as well as a heat function and possibly 24volts to power the thermostat, depending on what we can measure at these thermostat wire connections on the printed circuit board.

Most furnaces build since 1990 use printed circuit boards... earlier furnaces can present a problem without a wiring diagram to refer to.

We can go from there.

Expert:  Phil replied 1 year ago.

The issue here is the control voltage used, it can be 120 volts or 24 volts, if we connect your new honeywell thermostat to the incorrect control voltage it can destroy the thermostat, and possibly damage the rest of the controls in the system. That is why I need to know what you are connecting the thermostat to Braemar has made hundreds of different models over the years... without at least some photo's of the controls and some testing, attempting to wire a thermostat to it, in the dark so to speak can end badly.

Let me know, we can go from there.

Customer: replied 1 year ago.
Phil, for your future information the answer is, to use a Honeywell RTH7600 thermostat to control a Braemar heater using just the two wires, connect to terminals 'R' and 'W', polarity independent, and I won't even charge you for the details. Rob
Expert:  Phil replied 1 year ago.

Well thanks Rob.

My situation on this end however is that I need to make sure of what you have before I begin dispensing advice that might lead you to use your 24volt thermostat on a 230volt line voltage accordingly I absolutely have to ask for identifying information on your equipment before I can give good and safe advice.

that statement come to from me, age 74, 51 years in the business, the last 20 consulting nationally. I have learned not give advice blind.... it can be a life and death issue at times.

Congratulations however on sorting it out for yourself.

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