I would like to use 2 thermostats on one gas furnace. One for the gas furnace and the other thermostat to control just the blower on same gas furnace? Then put in an out door wood boiler with hot water heat in same gas furnace. 4 wire heat cool. I have a Lennox G61MP series. Need to know how to wire the thermostats.

Just purchase a two stage heat thermostat and follow the install instructions included with the thermostat. If a difficulty pops up with the install I recommend you contact a local HVAC company to do a ON SITE survey of your situation since this type of wiring can be difficult if not impossible to explain in this venue since so many different control and wiring combinations are possible. Better to be safe than sorry.

I'm not sure if my schematic downloaded. If it did you need to be careful not to run both t-stats at the same time. You have a 2 stage system right now and I can't guarantee if they both try to run some major damage won't happen. This is a very simply system I drew. I've installed some systems similar to what you want to do. I can tell you up front depending on what your burning (the temp of the water) it can get really hot . That limit switch will open and is suppose to shut down the system and won't be able to. It would take a solenoid valve to give you complete control of your system and depending on what type of boiler you have maybe a few more options. I just seen my file is to large to download. You can write me at "[email protected]" and I'll mail it to you

It does not seem your drawing downloaded to the board. Try again