Quote Originally Posted by Bcycling View Post
Trying to understand that diagram. So I plug my secondary "backup" into the wall, set it 4 degrees higher. Then plug my primary stat into the secondary stat. Is this correct so far?

then I only wire my heat tape to go into the primary correct?
Correct. The heat tape would be plugged into the primary thermostat. The exact setting on the secondary thermostat would need be played with to ensure it doesn't shut off the primary thermostat prematurely.