fishpick
Platinum Member
Negative. That's why geo is a "better" heat pump than air to air.I thought ...from others info that geo needed supplemental heat at approx the same level as a air to air ...more or less . mine switches to back up propane at 29 degrees or > 2 degrees diff in set point and temp.....hummm gotta keep that inspection in mind
With air to air - when the temp gets down around 20F, it's VERY VERY difficult for any unit to extract heat... there's something about a 40-50 degree temp differential is "doable" but other than that - the unit can't make heat. So if it's 20 outside and you have the house set to 70... you are off the high side by a fair amount and the unit can't satisfy - so it needs AUX heat because it can't produce enough BTU's.
So, I guess in a way that's true with geo - but the earth where the loop fileds reside (here) is a cool 42-45 degrees no matter what in the winter. So the laws of compressor physics still come into play (that whole 40 degree window) but the outside temp doesn't get to mess with things...
Where AUX heat comes in with geo is NOT when the heat pump can't make heat - it comes in when the heat made by the heat pump is leaving the structure faster than the unit can replenish it. (We have learned nuance is EVERYTHING with geo)