I'm no electrical wizard so I have no idea how the Herpstat would be affected by being plugged into an On/Off thermostat. I've heard of people using a dual On/Off thermostat and a thermostat with a dimmer but never a combination of the two styles. The Herpstats have a built in fault detector that shuts it off if it fails. To be honest, I think there is a greater chance that the BAH will fail long before the Herpstat will...