Cornelius UCR 700 Series service manual Expansion Valve, Adjustment and Troubleshooting

EXPANSION VALVE

You will find a thermostatic expansion valve on icemakers, which is used to control the amount of refrigerant flowing through the evaporator. Improperly installed or defective expansion valves may cause low production, soft ice, squeaking from evaporator and excessive load inside evaporator.

By using general refrigeration system troubleshooting along with the pressure charts you can easily determine whether or not the expansion valve is working properly.

ADJUSTMENT AND TROUBLESHOOTING

When troubleshooting the expansion valve you must first be sure you have adequate water flowing into evapo- rator, a clean condenser, unit is properly ventilated, and system is properly charged and free from any restric- tions. Also be sure compressor is operating properly.

Second, take reservoir water temperature and air temperature from condenser inlet and determine at what pres- sure unit should be running. Machines are equipped with thermostatic valves, there is NO adjustment. If correct pressure cannot be obtained, first be sure system has time to stabilize 10-15 minutes. Second, be sure sensing bulb is located at 12:00 position on outlet side of evaporator about 3-4 inches away from evaporator and be sure to insulate well and clamp tightly to tubing. If system pressures are still not adequate, take a second water and air temperature reading and go over other parts of system for possible problems. If proper charge is question- able evacuate and recharge to nameplate and leak check. If valve still malfunctions replace valve.

When replacing valve be sure to bleed refrigerant gas from low side port so as not to lose refrigerant oil. Use general refrigerant system practices when replacing and recharging unit. After new valve is in place, go through previous monitored adjustments and troubleshooting to be sure valve is functioning properly.

NOTE: Units with thermostatic expansion valve—The valve is located on bottom refrigerant line. Sens- ing bulb is located on top refrigerant line. On water cooled units adjust condenser modulating valve before troubleshooting expansion valve.

CAUTION: Very high discharge pressure is present in system. Quick disconnects on your gauges will minimize danger and loss of refrigerant. Comply with federal regulations for reclaiming refrigerant.

CONDENSER MODULATING VALVE

The reason for using a water modulating valve is to supply the correct amount of water to the condenser. and to maintain a proper operating pressure to refrigeration system high side.

The flow of water through the valve is increased as the high side pressure rises and is decreased as high side pressure lowers.

To calibrate the amount of water flow with the refrigeration system high side pressure, turn adjustment screw located on end of valve opposite of bellows. See Figure 6. Turn screw counterclockwise to raise opening point or clockwise to lower opening point. Opening point of valve should be set to maintain proper operating pressure in refrigeration system high side. Refer to Pressure Chart on page 3. Closing point of valve should be set low enough to close valve during compressor stand-by periods.

NOTE: Cold water will absorb heat faster than warm water. The water flow will therefore automatically increase as inlet temperature increases.

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