Open Dairy / Deli case freezing up
Had this problem going on for too long. We got a mom and pop grocer with a 48' open dairy/deli case. It is split into 2 separate systems, so that each 24' or case has it own cond unit. Case 1+2 has 4 30min defrost per day, and never has a problem. Case 3+4 has 4 45min defrosts and it froze up last night. Defrost timer works fine, air temp is in the high 30s with all defrosted and running good. Case 3+4 is near a set of swinging doors to the back room on the far right end cap. We had some heavy rain for the past couple of days, besides that it has not frozen up since the summer time. What do we need in this store to eliminate this? Dehumidification? Humidity in the store was at about 60% this morning. I am in upstate NY, was about 55 degrees outside yesterday with rain, and today clear and about 40 degrees out side.
I appreciate any advice you can give me.