Neither. This unit has a Calrod element in it, similar to a stove. Strip a 8" piece of #10 copper wire down to the bare copper and do a few wraps with the top end around the heater. Drop the distal end about 2" into the drain hole. That should warm the area up as the heater does its thing every 8 hours.
And consider checking your thermostat settings. If you have it turned down colder than normal, expect the drain to freeze more frequently. Humidity and door openings also affect drain freezing.