Very low condensing pressure
Anyone already tried/experimented with very low condensing pressures?
Idea (already tested with a small scroll compressor on R404a and a free-ar blowing evaporator) : make an earthcoil in copper (+/- 1,5 m or 5 feet deep), eventually some circuits of 5/8 to a header, condensing at 20°C to 22°C and evaporating at -8°C. Hughe COP. Even a efficient subcooling coil can be made this way.
Selecting TEV according to this little pressure difference must be possible or use of stepper motor EV or PWM Danfoss AKV.