Years ago, buddy of mine installed in his house, up here in COLD Alberta. Initially unit did not work well, and had it replaced under warranty, but then paid extra to get next size up . . . still had issues when it was like minus 25 and colder here . . . temp differential kept it from working correctly . . . great when it did work - could fill the hot tub with 120F water with no issue. But during the extreme cold snaps, had to take cover off it to let room temp help keep things warm . . .

Seems units are more designed for warm/cool climates . . . not damn cold winter types.