2. Before making any adjustments or repairs, ask the customer to describe the problem; then inspect the entire machine for any obvious defects. Look at the entire picture:
3. If you don’t see any visual defects, check the machine’s major components.
4. If you don’t find any problems in the water distribution system, examine the refrigeration system. Install both a suction and discharge gauge, and observe both pressures during the entire freeze and defrost cycles. The discharge pressure should be within the manufacturer’s specifications. A higher-than-normal discharge pressure can be caused by one of several problems, including but not limited to:
5. Observe the machine’s suction pressure, and even initiate the end of the freeze cycle by monitoring the suction with a low-pressure control. At the start of the cycle, the suction pressure will start out high and gradually pull down. Consult with the manufacturer regarding the proper pressure (values vary slightly with each machine). A higher-than-normal pressure may be a sign of an inefficient compressor, leaking hot gas solenoid valve, or overcharge of refrigerant. Lower-than-normal initial suction pressure can be caused by a low refrigerant charge, restricted system, or defective thermostatic expansion valve. As the water freezes and the evaporator temperature drops, the suction pressure will pull down and reach its final value just before the machine goes into the defrost cycle. If the machine goes into the cycle before reaching this final value, the ice cube slab may be too small and may fail to meet the manufacturer’s specifications. In this case, adjust the cube-size control and let the machine run longer in the freeze cycle. If the suction pressure drops below its designated value, the slab may be too large and difficult to separate from the evaporator plate during the defrost cycle. Most machines should be adjusted to form a 1/8-in. bridge on the slab, which allows the cubes to separate from the evaporator in one piece and then break apart easily as the slab drops into the bin.
6. If both the water distribution system and freeze cycle operate normally, check the defrost cycle. Hot gas from the refrigeration system discharge should bypass the condenser and thermostatic expansion valve and enter the evaporator. This warms the ice slab, allowing it to separate from the evaporator and drop into the bin. The water pump should also shut down to prevent the ice from becoming wet and the water from dumping into the bin. Suction pressure will rise during this cycle and should be monitored to make sure it stays within the manufacturer’s limits. If the pressure goes beyond the limits, the compressor could overheat and possibly damage the windings. If it is too low or does not change over from the freeze cycle, the slab may be unable to separate and fall into the bin. This can result from a defective hot gas solenoid valve (doesn’t open) or a defective cube-size control (doesn’t switch the machine into the defrost cycle).
7. After any repairs or adjustments are made, watch and time at least one complete cycle. Observe at least two cycles on any new installation. This ensures that the machine functions according to the manufacturer’s specifications, and that any adjustments or repairs were done correctly. Above all, ice machines should be cleaned regularly for continued proper operation, and the manufacturer’s cleaning procedures should be followed exactly.
Marchese is owner of Arctic-Air Refrigeration, Pittsburgh, PA. He can be reached at P.O. Box 97022, Pittsburgh, PA 15229; 412-734-4433.
Publication date: 11/05/2001