This is Turtle.

When i install a heat pump and set the outdoor thermostat to switch
from the pump to the back up fuel. i set it on or about freezing. so
here is a hart for the different people.

Rich and Don't want them to see any difference in the pump or fuel back
up. 40 degrees.

Normal people who want to try to save a little money and see about the
job being right. 32 degrees.

Poor People that need to save all they can and cut the cost a great
deal and don't care about seeing a little difference in the temperature
in the house. 20 degrees.

Pick out of the above to see what you want.

TURTLE