That’s a single door reach in refrigerator. It doesn’t have a defrost circuit. If you are experiencing icing, check the following
Thermostat setting to cold
Actual product temp in the morning at start up to be correct. 36 to 38F is ideal
Over usage. Loading hot open product or to many openings per hour
Door not kept closed and only opened as product is added or removed.
Overload. (effects air flow and thermistor sensing)
Verify thermostat is accurate with a known thermometer.
Evaporator fan is moving air and up to speed
Lastly, the controller is designed to not restart till the box gets to 38 degrees to facilitate a De-icing of the evaporator every cycle of the compressor. If your temp is set to 36 to 38 degrees it should shed ice over time unless you have a air flow problem. If ice is starting on one side and moving across you may have a refrigeration problem. Call a licensed refrigeration tech to check .