Ask Experts Questions for FREE Help !
Ask
    cwroenisch's Avatar
    cwroenisch Posts: 1, Reputation: 1
    New Member
    		  
    #1

    Jan 13, 2008, 07:20 PM
    Changing thermostats
    I am taking out a Lennox non-programmable thermostat for a programmable Honeywell Model 7500 programmable thermostat. When I remove the old thermostat there are only 2 wires attached to the device. When I asked honeywell about the wiring they asked if the old thermostat was 24 volts. There is no indication anywhere on the old thermostat as to the voltage. It is about 25 years old.
    Thanks for the help
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #2

    Jan 13, 2008, 08:42 PM
    Only two wires will probably need a battery operated thermostat or you will have to pull a constant hot from the 24 volt transformer.
    Frdbrkl's Avatar
    Frdbrkl Posts: 94, Reputation: 7
    Junior Member
    		  
    #3

    Jan 14, 2008, 10:20 AM
    Quote Originally Posted by cwroenisch
    I am taking out a Lennox non-programmable thermostat for a programmable Honeywell Model 7500 programmable thermostat. When I remove the old thermostat there are only 2 wires attached to the device. When I asked honeywell about the wiring they asked if the old thermostat was 24 volts. There is no indication anywhere on the old thermostat as to the voltage. It is about 25 years old.
    Thanks for the help
    They're probably trying to see if it's a "millivolt" system. Does your system have a transformer on it? If so, it's 24 volts. If not, it's a millivolt system and the two thermostats are for the most part incompatible.

    To run it off batteries-put batteries in it, connect one wire to R and the other to W, and you're done. To run it off a 24v transformer system (and lose the batteries) simply run one wire from R on furnace to R on stat, w on furnace to w on stat, and C on furnace to C on stat. Turn power back on, and you're done-except for programming.
Not your question? Ask your question View similar questions
 

Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.


Check out some similar questions!

Changing thermostats [ 3 Answers ]

I'am changing to a digital thermostats. The old one is honeywell but the wiring is different form the new honeywell.. old one Lr69071 has 6 wire y=yellow g=green o=ornage r=red w2=white and x=gray y g o r w2 x. The new one has rh rc w y g model# RTH230B. Do I have the right thermostat and...

Changing the outside unit vs. Changing the whole system [ 7 Answers ]

My outside unit leaks Freon and needs to be replaced. The system is about 9-10 years old. Initially, the contractor gave me a $2500 estimate to change the outside unit to a new Trane XR14. When the written estimate came, it included changing the coil and fan package inside (it's a ceiling unit)...

Changing Thermostats [ 1 Answers ]

I am replacing a "White Rodgers 1F94-71" with a "Carrier TSTATCCPHP01-B". The wiring on the White Rodgers is: O-Orange, Y1-Yellow, C-Black, G-Green, White jumper wire from Y-1 toW1, Brown jumper from E1 to W2, R-Red. The following are unused spaces:B,Y2,E2,L,&W3. The Carrier has...

Two Thermostats to One [ 2 Answers ]

I currently have a separate thermostat for the heater and the A/C... I want to combine them into one thermostat... I have replaced the thermostat before, but my knowledge of the wiring is very basic... My issue is that I have two "R" wires and I am worried about combining them together since it is...

Thermostats [ 3 Answers ]

I have recently purchase a home and I found two thermostats installed, they told me one controls de AC and heat and the other one heat only, They're located on different rooms. Can anybody tell me how can I replace this two thermostats into one? Thanks

View more questions Search