I have a Noma THM303M thermostat which I hooked up yesterday. I only had 2 wires and the manual states they can be reversed. The thermostat worked perfect yesterday, now today the furnace turns on and stays on.

Check for shorted thermostat wires. This will cause the furnace to run all the time.

The 2 additional wires are securely taped. The override on the unit does not work, but when the turn the switch from heat to off. The furnace will turn off. Effectively I now have a manual furnace.

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Originally Posted by briankshepherd

I have a Noma THM303M thermostat which I hooked up yesterday. I only had 2 wires and the manual states they can be reversed. The thermostat worked perfect yesterday, now today the furnace turns on and stays on.

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The 2 additional wires are securely taped.

What 2 additional wires? You never mentioned this in your first post