I just replaced a 15 year old Nova Cool 12v DC refrigeration
system because the aluminum roll-bond box evaporator failed due to corrosion
. The corrosion
caused a refrigerant loss.
The new system consists of a Danfoss BD35 complessor & condensor unit, and a 40 inch by 10 inch flat roll bond evaporator bent in to an "L" shape the evaporator is oriented vertically in the reefer box. The system is controlled by a Carel electronic thermistat. The BD35 is set to run at 2500 rpm
. No problem cooling
the 6.1 cubic foot box.
My question is in regards to the setpoint and differential for the Carel thermistat. The thermistat is sensing evaporator plate temperature. I currently have the setpoint at 16 degrees F with the differential at 17 degrees F. So the compressor
turns on when the evaporator reaches 33 degrees and shuts off when the evap temp reaches 16 degrees. Box temps are about 42 degrees at the top of the box and 36 degrees at center and vertical midpoint of the box (a little too cool). If I raise the differential above 17 I get icicles forming off the evaporator because it defrosts. Gut feel says I shouldn't let the evaporator defrost.
If I raise the setpoint and reduce the differential, I get increased cycling of the compressor
Am I on the right track here? The system runs 15 minutes on, and about 25 minutes off as presently set. Ambient daytime temps are 75 to 80 degrees F during the day.