Originally Posted by Denali
Remember, the "input air temp" is the temperature of the room being heated, not the outside temperature. The heat pump (in either heating or cooling mode) does not draw outside air into the house.
Not quite true
As above no air actually travels thru the unit but
The heat pump attempts to draw heat from the air outside and transfer it thru the heat exchanger to inside the unit. It becomes more difficult to extract heat as the temp drops and when it gets to some place above freezing it just gives up.
So turning on a heat pump in near freezing conditions will just chew electricity.
You will not get 20deg temp difference across the aircon as you would in cool mode.
Put it another way
When it's hot outside and you are in cool mode the unit is extracting heat from a hot motorhome and transferring thru the heat exchanger to the outside. There is generally a lot of heat available. In reverse there is very little heat available at 40f
There is no such thing as cold just a lack of heat
Would someone like to correct my analogy