Is there a 120 Volt switch that would shut down power to a dehumidifier when the outside temperature goes down to 35°F to protect the drain line from freezing. A digital thermometer would need to be mounted outside to detect the 35°F temperature to shut down power to the unit.
I install dehumidification systems to control interior environments after our mold remediation projects but here in the northeastern USA, the temperature freezes the drain lines and the units no longer have a self draining operation.
Best Answer
You can wrap the drain line in electric pipe heating tape to prevent it from freezing:
You should be able to find it at your local home improvement store.