Finding: Evaporator blocked by frost.

Cause: Lack of or poor defrost procedure.

Action: Install defrost system or adjust defrost procedure.

Cause: Moisture from unpackaged items.

Action: Recommend packaging of items or adjust defrost procedure.

Cause: Moisture from air ingress into room through fissures or open door.

Action: Repair fissures. Recommend that door be kept closed, or if it needs to be open, fit supplementary plastic strip curtains.

Finding: Evaporator damaged

Cause: Fins deformed.

Action: Straighten fins using a fin comb.

Finding: Evaporator inlet frosted and TXV covered by frost or ice

Cause: Refrigerant supply to evaporator too small because of too small orifice.

Action: Check if a bigger orifice will bring the superheat down and show more constant (refrigeration application) or no icing (air conditioning) picture.

Cause: Refrigerant supply to evaporator too small because of too high superheat.

Action: Set thermostatic expansion valve to a lower superheat setting.

Cause: Refrigerant supply to evaporator too small because of partial loss of bulb charge.

Action: If the charge or most of it is lost, warming up the bulb will not open the valve (if the full charge is still there it will open (valve without MOP)). Change expansion valve if charge is lost.

Cause: Refrigerant supply to evaporator too small because of dirt strainer partially blocked.

Action: When changing/removing the orifice, check if dirt blocks the valve - clean it.

Cause: Refrigerant supply to evaporator too small because of orifice partially blocked by ice.

Action: Do a hair dryer test on expansion valve (body, near orifice). If afterwards the unit runs perfect for some time, it might be ice-formation at the inside of the orifice. If it is ice, exchange refrigerant and dryer or at least filter drier (if necessary more than once).

Cause: Refrigerant supply to evaporator too small because of fault described under "Vapor bubbles in sight glass".

Action: See "Vapor bubbles in sight glass".

Cause: Refrigerant supply to evaporator too small because of defect TXV.

Action: Replace thermostatic expansion valve.