I also have a question about how a 2 stage TStat works. In particular, I'm interested in information on how a Honeywell RTH7400 works with respect to it's stage 1/2 heat/cool algorithms. Is there a PDF file on-line somewhere that explains it?
My equipment is an Amana AMV80905CXB/ASX160361A. The fan is set to profile D, i.e 50% for 30 seconds, 82% for 7.5 min, 100% until done, 50% at the end. The fan is set for 1210 CFM (3 ton) high speed. The low speed spec at 787 CFM. (This is the B+ setting.)
I would like to understand when the TStat should switch between low and high demand. And I'd like to understand what fan blower speeds I should expect during that process and the interaction between high/low stage speeds and the profiling.
My guess, for cooling, based on 787 low speed and 1210 high speed:
787*50% for 30 seconds, 787*82% for 7.5 minutes, 787 until set point reached or after some time (how long?) if set point not reached then 1210 until set point reached, then 50% of either 787 or 1210 depending on if stage 2 was used for the final 30 seconds.
I have two newly installed units. The current behavior on both units is that it's always running at 1210 (modified by the ramp up/down of profile D). I've never noticed the outdoor unit fan speed at anything other than a single fan speed.
At least for one of the units, which from the bedroom I can easily monitor at night, it comes on for about 4 minutes and shuts off. It seems this is way too short a cycle.
Also, one of the units (the other one) gets into a state where the fan stays on a low speed for a very long period of time but the compressor doesn't kick in.