Interesting. Calder's article said nothing about the ASU monitoring
anything but system voltage. My thought was that the ideal control would
monitor box temperature, evaporator temperature and cycle time. That way it
could sense when the box had been loaded with warm items and react faster to
frequent opening. Strictly time based algorithms take several cycles to
adjust to changing conditions. Reading the latest Isotherm literature it
looks like the ASU comes pretty close but it seems oriented towards holding
plates. Apparently the ASU replaces the whole power unit where the SSC just
varies the thermostat circuit resistance.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

wrote in message
ups.com...
The Isotherm ASU system is a progressive speed adjustment based on
evaporator temperature feedback and efficiency adjustments has nothing
to do with voltage. The Automatic Speed Up function is an extra bonus
to the automatic temperature speed control. Advancing compressor speed
when a charging current is available will store additional surplus
energy in the system's holding plate. I do not see how anyone could
believe that the SSC is better than the ASU
from the tests that I have run. I recommended Danfoss's AEO first as
it is a Completely new module. My second choice was Frigoboat's SSC
over Isotherm's ASU for two reasons, Isotherm will not sell their
unit separate you must buy a complete system and the ASU has limited
control when the tropical heat load exceeds its automatic adjustment
range.