Replace thermostat have a 30 some odd old lennox thermostat want to replace with honeywell 5000 series lennox installer used a color code of his own 2 AC guys have said so what i would like would a terminal conversion lennox is using terminals R V F M L A Y new honey 5000 has terminals Y2 W2 G W C Y R Rc conventional or L E AUX G O/B C Y R Rc R&Rc jumped PLZ HELP

SOURCE: RTH7400 thermostat installed-screen display unlit-used

w2 and y2 are used for 2stage applications

w2 = 2 stage heat
y2= 2 stage cool

If your system is a single stage system, look for the y1 and y2 terminals. If the thermostat does not have y1 and y2 then you may have the wrong thermostat. As always, please read the directions carefully. Thanks!

SOURCE: Thermostat Wiring: W2? E? Where to connect?

You have a heat pump. You need a thermostat for "Heat pump with Electric back-up heat". Make sure the 'stat has either an "aux" (auxilliary heat) or an "E"(Emergency heat) terminal. The wiring instructions will be provided with the thermostat.

carl carpenter

• 82 Answers
• Posted on Jan 05, 2009

SOURCE: Replacing a Williamson (White Rogers) Termostat

rh is power for cooling terminal and rh is power for heating terminal connect red wire to rc or rh and there should be a jumper between rc and rh if not install one all other wires are color coded correctly. now the blue wire is not used.

SOURCE: Upgrading Thermostat

Looks like your system is a heatpump system and that t-stat will not run a heatpump , you need a t-stat for 2heat and 1 cool systems

SOURCE: Change thermostat

You have caught me without my old books, but I can tell you the orange wire is for the reversing valve on a heat pump. Almost all manufacturers, except for Lennox, are: R=Power (24volts), G=Indoor fan (Blower), Y=Cooling (A/C), and W=Heat. Some t'stat's are set up to use 2 separate transformers (24 volt), that is why you will see Rc, Rh. This is power for cooling and power for heating. If this is what you have, just take the Red wire and strip it back far enough to go under both screw terminals if the unit is a residential one. I've been doing commercial work for over 20 years and have never seen an "A" terminal, so I can't help you there. You may want to double check that. If I'm reading you correctly, I would put the orange wire on the "O" terminal. Don't understand why the "Y" terminal is not used. It turns on the compressor. The "O" goes to the reversing valve to "Tell" the outdoor unit that it is either in the cooling or heating mode.

Good Luck and let me know if I can help any further.