Replaced an old Honeywell round thermostat (mercury type) with RTH2300. There were only 2 wires (no color coding) coming out of the wall, so I called Honeywell to find out how to connect them. They told me to connect the wires to R and W, so I connected like that. I set the daytime temperature to 18 degrees. The heater started running, and the room themperature went above 20 degrees, but the thermostat didn't turn off the heater. What is the cause of this non-stop heating? Should I remove the jumper between R and Rc? Honeywell said I didn't have to remove it.