There is an expansion valve at each holding plate. You could probable adjust the expansion valve to a completely closed position.
I had a Grunert two plate electric
drive system, it had two thermostats and electric
valves to turn each plate on independently. I replaced it about ten years ago with a modern evaporator plate system (AB cold machine). Temperature stability is much better. Power draw is much less. Probably removed 200 LBs from the boat
. Since the Grunert drew 40 amps while running and the new units draw about 5 amps each (for much longer run times of course) the batteries
are less impacted and during daylight the solar
more than satisfies the demand. I had the Grunert on a timer that would run it twice a day, it would run for about 45 minutes each run.