Air infiltration
Short definitionThe load brought by warm, humid air coming in each time the door opens. Door type, strip curtains and an anteroom reduce it.
Every time the door opens, cold air flows out at the bottom and warm air comes in at the top to replace it. Both the temperature of that air and the moisture in it are load. The moisture turns to frost on the evaporator.
The ways to reduce the load are well known: do not make the door bigger than it needs to be, use a PVC strip curtain or a high-speed door, and put an anteroom in front of the room.