Heat pump for spa in colder temperatures


Jul 2, 2020
I'd like to get some advice for using my heat pump (ultratemp120) with my 600 gallon spa as it gets colder (first season for me).

My first experience did not go well... I turned the heat pump on around 3:00 in the afternoon as the temps started going down to the forties. Heat pump finally stalled out at 91 degrees and could not get any hotter. Heat pump would run just a short 1 minute cycle and then shut off.

Since then I have realized that you need to heat during the hottest time of the day and maintain from there. So heat pump on at noon, and have been able to maintain 99-100 through the evening.

So any tips and tricks I don't know about? Any standards (outside temps) for when you just can't use the unit? Any settings to change to make sure I'm not damaging the unit trying to run it when it shouldn't be running? TIA.
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