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    SeanOg's Avatar
    SeanOg Posts: 3, Reputation: 1
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    #1

    Jan 2, 2009, 09:28 AM
    Wiring a thermostat with one R terminal with two transformers
    I just bought a White Rodgers IF8RF-275 wireless remote sensor thermostat. It has only one R terminal, while my old system had a Rh and a Rc. I have an oil furnace hot water heat and a central A/C system. Each has its own transformer. How DO I wire the thermostat?
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #2

    Jan 2, 2009, 10:34 AM
    No such model number listed at White Rodgers. Please check exact number.
    SeanOg's Avatar
    SeanOg Posts: 3, Reputation: 1
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    #3

    Jan 2, 2009, 10:40 AM
    Sorry, 1F85RF-275
    KC13's Avatar
    KC13 Posts: 2,556, Reputation: 99
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    #4

    Jan 2, 2009, 12:11 PM
    I would suggest you start with the correct thermostat for this application. It'll be a snap from there. It'll also be a snap with what you have now, followed by some smoke, then cooler indoor temperatures.
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
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    #5

    Jan 2, 2009, 04:12 PM
    KC-13 is correct. There is a way for a professional to combine both transformers to work on one R terminal but for you to attempt that would probably end in a smoking disaster. Get the correct thermostat and BTW I still do not find that number listed at the WR main web site or in my electronic catalogue.
    SeanOg's Avatar
    SeanOg Posts: 3, Reputation: 1
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    #6

    Jan 2, 2009, 04:59 PM
    Thank you. Do you guys know of any remote sensor thermostats, preferably wireless that have the rh and rc terminals and are battery powered, not battery backup?
    KC13's Avatar
    KC13 Posts: 2,556, Reputation: 99
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    #7

    Jan 2, 2009, 05:03 PM
    One that meets all that criteria? Not me.
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #8

    Jan 2, 2009, 06:01 PM
    Just put on a factory seminar for Venstar brand thermostats. They have nice remote control setup that could be modified to your needs. During the seminar I produced a wiring diagram to eliminate this problem. You could have a professional HVAC contractor eliminate both 24 volt transformers and replace them just one transformer. This eliminates the problem and will offer you the benefit of a much larger selection of wireless units.

    All of the thermostat wireless units hand held controls are battery operated with only the receiver needing power from the 24 volt supply. Since the receiver can be mounted almost anywhere this eliminates that problem.

    As a side benefit by having a professional change over the low voltage from a two to a one transformer system the smoke problem goes away.

    Venstar Inc. - Thermostats
    Venstar Inc. - Thermostats
    MarkwithaK's Avatar
    MarkwithaK Posts: 955, Reputation: 107
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    #9

    Jan 2, 2009, 06:04 PM

    Remote sensors make me cringe, wireless or otherwise.
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