This is kind of a general question and the specifics for particular
brands/units might be all over the place. I'm in New England, where
we have ice storms and weird "snowpocalypse" events and power
failures from a half-second to a week, and it would seem to me that
if a heat pump with an outdoor unit and an indoor unit *equipped with
heat strips* loses functionality in its compressor side, that the air
handler should be able to at least heat the house a little from the
resistance strips on its own. The question: are most systems able
to do this, once they're configured to know that they have the
resistance heat capability? Will they revert to that "emergency"
operation if the outdoor unit has some showstopper problem?
This would seem like essential functionality, because a system
might be keeping an unoccupied house from freezing down and
we wouldn't want an issue in the greater complexity of the heat
pump completely disable something that could still run and
provide heat in a simpler [but more expensive, sure] way when
needed -- at least until the main system gets fixed.
I ask because I was trying to experiment with this on the Daikin
last night, outdoor unit powered down, ambient around 60 and
indoor still around 70 but I pushed the setpoint way up to see if it
would do the right thing with the installed 3 kw heater. It just sullenly
sat there with its "U4" error and didn't do squat. What would you
expect the right behavior to be?