1965 radiant floor heat with new thermostat

ihave3abc

We have thoroughly enjoyed the in-floor heating our home has but last year I wanted to update the 1965 thermostat. I could not for the license to figure out what exactly I should replace it with when an electrician friend said all I needed was a standard mechanical thermostat, basically something that could control a baseboard heater. Wanting to test out what he said, I pulled an outdated (from the 90's) thermostat from the garage and tried my best to wire it like the original wiring. Much to my surprise it worked. Fast forward to last week and just before our home appraisal I pulled off the thermostat because I finally had a nice new thermostat to replace it with. Stupid me did not take any photos or label anything as I was in a hurry and removing the old thermostat. Now, I cannot for the life of me figure out how to get this new one wired to our in floor heating. Our box has 1 set of load wires running in and two sets of red wires coming from the heating in the floor.  Can anyone help me out?

*ETA* I know nothing about the actual heating under rhe floor....I cannot provide any specifics about it 

Jamie Hall

Well, that's a bit vague... however, it is likely that the radiant floor is electric, and the thermostat switches the power to the floor. That is also kind of vague -- deliberately. First, you need to find out what the voltage of your two feed wires really is. Depending on where you live, it may be 120 volts or it may e 240 volts (that's nominal voltage -- yours may vary slightly). Then you need to have at least some idea as to how much current the floor demands, so that you can find a thermostat which can handle that much power (the baseboard heater thermostat you mentioned probably can). Third, there are two possibilities here -- depending on the voltage. One is that both your incoming feed wires are hot, and therefore -- at least in my view -- the thermostat should control both sides. On the other hand, if it's 120, one of those wires is a neutral and must NOT be switched by the thermostat. Fourth, are there any ground or other neutral wires present? They need to be properly identified -- and proprerly connected.

On the whole, this is not a really great project for someone who is not familiar with and comfortable with power electricity...