Dealing with excessive frost/snow begins with looking for the area where warm, moist air could be entering the cabinet. This is generally caused by improperly sealed pipes or electrical penetrations. Resolving this issue simply requires properly sealing these penetrations. If frost is developing around the door, ensure the door is closing and sealing properly and that its heaters are operational. Worn door gaskets or a defective door heater are common causes of frost developing around a door. 

Ice forming on a drain line or around the evaporator drain pan is most often caused by a cracked or plugged drain line or a defective drain or pan heater. Again, the location of the ice may be the key to identifying the cause. Ice forming just on the drain line may be from a cracked line; however, icing at the drain pan can be either a plugged drain or a defective heater. 

Ice droplets forming around a fan shroud guard or on the ceiling in front or around the fan(s) is normally caused by a defect in the defrost control. Either 1) the defrost cycle is too long and terminating based on time and not temperature; or 2) the fan delay is bringing on the fan too quickly, causing water vapor to be blown off the evaporator coil and into the case where it refreezes and forms ice droplets. To isolate the problem, run a defrost cycle and verify the defrost cycle terminates based on coil temperature, generally around 55°F. Once the defrost cycle terminates, verify there is a delay before the evaporator fans come on again. They should come on after the evaporator coil drops below freezing, generally around 25°F. 

Lastly, walk-in freezers will have a heated air vent close to the door opening. This helps maintain similar air pressure inside and outside the case; otherwise, the lower temperature inside could create a vacuum, making the door difficult to open. When the heater fails in these air vents, frost can develop around the vent. 

Solving frost or ice issues with a walk-in freezer is generally not difficult but will require a thorough inspection to find the root cause of the issue.