My wife and I got new HVAC (dual fuel: heat pump + furnace) system back

in July. Now that it's getting cold in Northern Virginia, I'm
wondering if I should make any adjustments to the settings.
Specifically, the control unit has a cold-lockout temperature for the
heat pump. This is the outdoor temperature below which the system will

bypass the heat pump and go directly to the furnace for heat.

So the question is, what (if anything) should I set it to? Is there
some sort of rule of thumb?

The heat pump is a Carrier Infinity 17 with an HSPF of 9.5. I looked
through all my documentation but didn't find any sort of efficiency
graph. I read somewhere that they're sometimes on the unit, itself,
perhaps inside the service door.

If anyone has some wisdom to share, I'd sure appreciate it.

Thanks in advance,
Bill Woessner