3 wire Thermostate install. White black red
We purchased a older home with boiler heat. There old thermostat was not connected. There are 3 wires: white, red and black. I purchased a Honeywell RTH2300 model and connected the wires to Black - B, white - W, Red - R. The Booiler stays on and the room is now 81 despite have the thermostat set at 65 HOLD. The oly way to control the heat is to switch off the heat switch on the thermostat. My guess is the back wire must go into one of the other colored Jumpers or does the black wire not get used?