I am trying to change Lennox to Honeywell

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Here you can find all about Honeywell RTH3100C like wiring diagram and other informations. For example: thermostat wiring diagram, installation manual, installation, thermostat, wiring, manual.

Honeywell RTH3100C manual (user guide) is ready to download for free.

E Back up heat/ white wire
AUX Jumper to E
Y yellow wire / Cooling - compressor
G Indoor fan Green wire
O Reversing valve energised in cooling most units Orange wire
L unknown. consult your manual Leave open
R Main power Red wire
B Reversing valve energised in Heat Rheem units only.
C Common second leg of power Blue wire.

well the wire on x will go to e thr r is the red wire goes to r the wire on f willgo to g the y will go to y now the rest you'll have to verfy at air handler o will go to reversing valve common wire will go to c the electric heat will go to aux

Color ---> New stat terminal

Blue--------C
Green------G
Yellow-----Y
Orange----O
Red---------R
White------E and Aux.
Tan---------unused, tape and secure it

If there is Rh and Rc or R and Rh, these terminals should be jumpered together.

I used to install Weathertrons eons ago. Whatever you do DO NOT connect the blue wire to the B terminal, you will short out your low voltage transformer immediately when you switch to heat

Hi, If indeed you do have a heat pump, there wouldn't be any gas involved as a heat pump runs on freon with a reversing valve and heat strips for aux and emerg. heat. For gas electric operation thermostat terminals are rc to rh with factory jumper. Red wire to either.W to W for Heat, Y to Y for cooling G to G for Fan. If you have a blue, you wont need it unless this is a commercial stat useing a common for the Led lights on the stat. The unit will get its 24volts through R terminal in combination with y,w,and,g. Cant be a heat-pump if you have a gas furnace.Wrong t-stat. You need a gas /elect stat. And on a 24volt programmable t-stat, the batterys are used for the program only.If the batterys die, than you will loose the program on most residential stats. On commercial stats with the common in play, when batters die the stat defaults back to the factory settings.If you had a Lennox heat-pump stat on a gas/elect unit, you need to change it. Someone was using what they had on hand. Let me know if this has helped you.I will be here if you need me. Sincerely,
Shastalaker7

Bill ..You dont have a heat pump.This controller will not work for a conventional system. Get the right thermostat

Take white off of Aux, and attach it to L

HONEYWELL WEBSITE:
Go to honeywell.com
Under red welcome sign
Bottom red highlighted box literature/image search
Type in thermostat model number
Click on arrow to right
Then click on the PDF files owners manual / installation instructions

both thermostatats will have terminal designators R,W,Y,G, possibly O/B, C, W1,W2, Y1, Y2, etc.
Simplest method is to remove wires from old stat one at a time. mark where they came from and then install at same desinated terminal on the new t-stat. Hope this helps. be sure to shut off power supply to the unit (furnace) first. The wire coming to the R (RH,RC) terminal is the 24 volt a/c hot, all others are feeding back to perform given function.

if you have a newer t-stat your heat pump reversing valve is either o or b depending on the type of system you have