Hi folks, I got a heat pump installed at my home and I'm looking to better understand when/how it switches over to backup fuel in the winter.
My unit is the LENNOX ELITE EL18XPV SERIES, which I found heating specs on here
It is installed in conjunction with a heating oil fired boiler and an aqua coil as the backup heat source. When it was installed, I asked, and the installer indicated that the heat pump will switch over to the boiler at about 37F. What I don't fully understand though, is that this unit was billed as a variable speed/inverter, so it seems it should be able to run at lower temperatures than 37. The website above seems to indicate it should produce 31,800 BTU/h at 17F, so can I set the "switch-over" temperature of outside to be lower to use less oil?

I have 2 standard freestanding units in my basement and crawlspace running 24/7. I want to get something more energy efficient, will last a while, and that's easy to maintain. I am considering an Aprileaire dehumidifier. Based on this https://www.energystar.gov/productfinder/product/certified-dehumidifiers/results it would appear they have a high efficiency rating. Does anyone have experience with these or recommendations on solutions?