A common mistake made by HVAC/R technicians in ice machine diagnostics is thinking ice build up in the machine is caused by low refrigerant charge. While ice build up can be a sign of low charge, it is always a sign of low pressure.
Problem: The technician is called about a machine not keeping up with demand, opens machine sides to inspect and sees ice build up on the suction line.
Misdiagnosis: The technician immediately starts to question the refrigerant charge, or worse, actually adds refrigerant (never add refrigerant to a closed system without locating and repairing any and all leaks). This stems from a common misconception that iced lines means low charge.
The build up is more than likely associated with the extended run time than low charge. The lower the refrigerant pressure, the lower the refrigerant temperature. In the case of an ice machine, the refrigerant must operate below 32 degrees F, this is the only way to freeze water. In reality, the refrigerant is probably operating between -15 and 10 degrees. So if ice is formed, go back to the original complaint of slow production.
Tech Tip: Ice build up is often caused by extended run time from a dirty evaporator, not the refrigeration cycle. Try cleaning the machine according to manufacturer procedures.