Is your coil ON TOP of your blower? Should be below the blower. Otherwise, you aren't allowing the heat pump to raise the temperature as well as it should.
Temperature rise @240V, 1200 CFM:
4.8KW=13, 7.2KW=19, 9.6KW=25, 14.4KW=38, 19.2KW=50
The difference between your two aux heat numbers (150 and 136) makes me think that you've got 14.4KW strips. I also think that you might have picked up some radiant heat from the elements/coil. Can you measure it immediately after a turn (perhaps a bypass humidifier duct)?
Coil is indeed below the fan. Electric strips are above the fan.
Air handler cfm ranges between 1490 (at .1" static pressure) and 1205 (at .5" static pressure). Not sure what I have, but all-metal ducts and 2 levels of living space (1600 sq ft) makes me think I'm at a low static pressure figure.
I have 10 kw aux heat for the heat pump, 15 kw total emergency heat.
I will retest. The 150 degrees seems too high for 10 kw of aux heat. Maybe the t-couple wire was too close to the electric strips for an accurate air temperature.