"DS King" wrote
How do you get the evap & condensing temps? Very few AC units have that
kind
of instrumentation.

Doug,
the original unit is a $90 window shaker from Walmart. I
installed the pressure access ports after I removed the condensing coil. I
had to braze the refrigerant line into my tube-in-tube, and I needed a way
to purge with nitrogen while brazing, and then attach vacuum pump, and
finally, charge the unit. So I had refrigeration gauges on the system
during testing. I converted the pressures to saturated temps using the R-22
pressure temperature relationship charts. I also installed temperature
sensing wells at various points in the system, and inserted thermocouples in
them to get feedback. The superheat and subcooling values are calculated.
I actually measured the gpm by opening the loop and measuring the volume
against a stopwatch. The delta T on the water supported the actual gpm of
the closed loop.
After testing I removed all but an ammeter and a discharge air thermometer.

Also curious: how many feet of copper tubing in your secondary heat
exchanger?
about 22' I shaped it as a triangle for storage purposes, 18" per
side, about 5 rows deep. The delta T I referred to is in/out of exchangers.
The delta T for 'baywater' vs cooling water is about 10 degrees.
Scout