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?
You can, but the lower you go (usually starting around 30F), performance degrades, with around 15-17F being the lower limit that you can run it in heating mode and still pull heat out of the outside air.
Ideally your aux heat would only be needed on those more extreme days.