[jeff5may]

Dremd,

Another thing to consider doing with the smaller units is using them in "reverse polish" mode. I have found that the heat exchangers in the smaller units can only be pushed so hard before they become the bottleneck in your quest for high efficiency.

The outdoor heat exchangers in these units are designed for massively more airflow and exchange area than the indoor coils. By installing the unit backwards in the window, reversing the connections at the compressor, and adding to the smaller (now outdoor) exchanger to gain heat transfer, you can run the unit at a lower speed to save motor energy while still pumping maximum btu's. This also has the benefit of being able to work on the unit indoors where it's a comfortable temperature. Most window openings are at a height where you can comfortably sit in a chair or barstool to do work and take measurements.

Don't laugh, this works, really! I am using this method to do testing of some suction line heat exchangers now. It really helps your patience factor when you're in a normal environment. No need to worry about rain, snow, wind, heatwave, frostbite, etc.