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What happens if a thermostat is wired backwards?

What happens to a thermostat if wired backwards, meaning supply power wired to the LOAD side and the LOAD wired to the LINE side?

Nothing would happen if a thermostat is wired backwards. The thermostat will NOT be damaged in any way, including a the screen being black. That is because the thermostat’s relay is “normally open”, meaning there is no path for electricity to travel, so voltage would be present, but would stop there. The thermostat’s relay has to be closed in order for the circuit to be complete and current to flow.

The screen MUST have voltage on the LINE side, otherwise it will not power up. If a blank screen, confirm voltage on the LINE side. If voltage is present and the screen is blank, the thermostat would be in error.

What happens if a thermostat is wired backwards?

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