So I was wanting to install all new thermostats for my radiant ceiling heat in my house, just so they look more contemporary. I bought one rated for 120-240 V just as the current ones are. However, I went to replace it today, and what I seen behind the thermostat was something I had never seen before. The old thermostat has 4 black wires coming out of it. One is connected to a black wire coming out of the wall, one to a white wire, and the other two are connected to two different red wires coming out of the wall. The new thermostat that I bought only had one black wire and one red wire. I'm confused. I had no idea how to replace this thermostat. I took pics but for some reason, the site keeps telling me that it they are not valid image files although they are .jpg's.