I have two heat pumps, one for the first floor, one for the second floor.
They are identical as far as I know. The outside units are located side by
side (about 3' apart). Recently I noticed that, on humid days, when frost
forms on the outside units, one of them will have a uniform layer of frost
from the top of the coils to the bottom, while the other has frost only on
the top 3/4 of the coils. Might that indicate a less than full charge on
the unit that develops no frost on the bottom 1/4 of the coils, or any other
problem? Or is it normal? I've lived in this house less than two months,
after 19 years in a house with gas forced air heat, so there's a lot about
heat pumps I don't know yet.
Impossible to tell from what you posted. You dont even know if the two
units are exactly the same. Did you ever think to maybe bend down and
read the model numbers to see if they are the same? NO, I didnt think
so. That would take some effort on your part.
Is the temperature and humidity on the first and second floor exactly
the same at all times? Do both units come on at exactly the same time?
Run the same length of time? Shut off at the same time?
It could be low charge, overcharge, poor air flow, excess air flow or
they could both be running perfectly fine.
Find a good tech that knows how to do superheat, subcooling, static
pressures and can read charging charts.
Simple enough, eh?