I have an Evcon fossil fuel kit (3024-7481-E) with a coleman/evcon two bulb mercury stat. There's a york heat pump, paired with a coleman furnace. I'd like to put on a honeywall stat, but can't figure out exactly what is what.
I know what the r,y,g,and o are. I'm just not sure what w2, B, X, and L are on the old stat. I would assume one is for the heat pump heat, and one is for the gas/emergency heat, but can't figure it out for sure. please help.
R = Power
Y = Compressor Contactor
G = Furnace/airhandler fan
W2 = Second Stage Heat, most likely used to run the furnace instead of heatpump in your case
W = Normally regular heat
For the heat from the pump, the circuit between Y and R is closed. O is the reversing valve - it is energized along with Y when cooling only.
I suggest that you call a technician. Wait for someone else to verify the info posted here.
Heat pump stats are confusing. We make good money cleaning up after HO's try to wire their own!
From what I see in my HP stat cross reference book, B is used for defrost on some old units. I'd skip it. X is common, sometimes B and sometimes C. L is a fault light, rarely used.
Follow at your own risk. If you fry something, you're on your own!
Personally I'd try to find a Honeywell Vision (home stores) or Vision Pro (sold through dealers).
Go with a vision pro tstat, have to be a contractor model as you will need one with 2 stages of heat to run both the furnace and heatpump. If you go with a vision pro you can ditch the fossil fuel kit and use a outdoor temp sensor wired to the thermostat to cut out the heatpump and changeover to furnace when temps are below the temp you program. They work very well and are extremly easy to program.
"Go big or Go Home"
Call a contractor, you don't want to pay for the more expensive repair if you short out the boards in the furnace or heat pump.
In order to use a vision pro properly with its duel fuel set up, the fossil fuel kit would need to be btpassed.
This is NOT a diy project.