I have a thirty yr old rheem electric furnace. The only way to shut off heating cycle is to shut off breaker, appears a new heat cool tstat has been installed, I have two wires from furnace connected to "rh and w" on tstat.

Try disconnecting one of the wires off the thermostat and see if it still runs.

I had removed one of the wires and it still operates.

You have a thermostat wire shorted or the furnace activating device is stuck or burnt closed/defective.

Next try to disconnect one of the thermostat wires where it ties into the furnace. This will eliminate the thermostat wire completely from controlling the furnace. If the furnace stops working when the thermostat wire is removed from inside the furnace then you know it is the thermostat wire that is at fault. If the furnace keeps running then you know that a sequencer/relay in the furnace is at fault.

I have a thirty yr old rheem electric furnace. The only way to shut off heating cycle is to shut off breaker, appears a new heat cool tstat has been installed, I have two wires from furnace connected to "rh and w" on tstat.

hvac1000,
Did pdbrowne fix his problem? I just started having the same problem on 30 year old rheem unit too. Wonder where the relay switch is and if one can still get one?

Thanks HICH