Hi,

I have my house has a very old gas powered gravity floor heating unit. The thermostat is also pretty ancient a manual ITT no. T80BV100J. Pilot is lit and I can feel a teeny bit of heat coming up, but it won't kick on when I turn the thermostat control on/up. My guess is that maybe the thermostat needs to be replaced, but not sure.

Thanks,

JG

That should be a 2 wire system with the thermostat just acting as a switch. Remove one of the wires from the thermostat and connect it to the other. If the heater comes on, it is the thermostat. If it doesn't, it is either bad wiring, a break or rodent damage or a gas valve issue. On an old unit like this, I have seen people bypass the gas valve completely and use a hand turn valve, similar to gas logs to cycle the heater. Not recommended but has been done.