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Restricted Refrigerant System Troubleshooting a restricted refrigerant system can be difficult. The following procedures are the more common problems and solutions to these problems. There are two types of refrigerant restrictions: Partial restrictions and complete restrictions. A partial restriction allows some of the refrigerant to circulate through the system. With a complete restriction there is no circulation of refrigerant in the system. Restricted refrigerant systems display the same symptoms as a “low-charge condition.” When the unit is shut off, the gauges may equalize very slowly. Gauges connected to a completely restricted system will run in a deep vacuum. When the unit is shut off, the gauges will not equalize at all. A quick check for either condition begins at the evaporator. With a partial restriction, there may be gurgling sounds at the metering device entrance to the evaporator. The evaporator in a partial restriction could be partially frosted or have an ice ball close to the entrance of the metering device. Frost may continue on the suction line back to the compressor. Often a partial restriction of any type can be found by feel, as there is a temperature difference from one side of the restriction to the other. With a complete restriction, there will be no sound at the metering device entrance. An amperage check of the compressor with a partial restriction may show normal current when compared to the unit specifi cation. With a complete restriction the current drawn may be considerably less than normal, as the compressor is running in a deep vacuum (no load.) Much of the area of the condenser will be relatively cool since most or all of the liquid refrigerant will be stored there. The following conditions are based primarily on a system in the cooling mode. MeTeRING DeVICe Capillary Tube Systems All units are equipped with capillary tube metering devices. Checking for restricted capillary tubes. 1. Connect pressure gauges to unit. 2. Start the unit in the cooling mode. If after a few minutes of operation the pressures are normal, the check valve and the cooling capillary are not restricted. 3. Switch the unit to the heating mode and observe the gauge readings after a few minutes running time. If the system pressure is lower than normal, the heating capillary is restricted. 4. If the operating pressures are lower than normal in both the heating and cooling mode, the cooling capillary is restricted. COMPReSSOR CHeCKS WARNING ELECTRIC SHOCK HAZARD Turn off electric power before service or installation. Extreme care must be used, if it becomes necessary to work on equipment with power applied. Failure to do so could result in serious injury ordeath. locked Rotor Voltage (l.R.V.) Test Locked rotor voltage (L.R.V.) is the actual voltage available at the compressor under a stalled condition. Single Phase Connections Disconnect power from unit. Using a voltmeter, attach one lead of the meter to the run “R” terminal on the compressor and the other lead to the common “C” terminal of the compressor. Restore power to unit. Determine l.R.V. Start the compressor with the volt meter attached; then stop the unit. Attempt to restart the compressor within a couple of seconds and immediately read the voltage on the meter. The compressor under these conditions will not start and will usually kick out on overload within a few seconds since the pressures in the system will not have had time to equalize. Voltage should be at or above minimum voltage of 197 VAC, as specified on the rating plate. If less than minimum, check for cause of inadequate power supply; i.e., incorrect wire size, loose electrical connections, etc. Amperage (l.R.A.) Test The running amperage of the compressor is the most important of these readings. A running amperage higher than that indicated in the performance data indicates that a problem exists mechanically or electrically. Single Phase Running and L.R.A. Test NOTE: Consult the specification and performance section for running amperage. The L.R.A. can also be found on the rating plate. Select the proper amperage scale and clamp the meter probe around the wire to the “C” terminal of the compressor. Turn on the unit and read the running amperage on the meter. If the compressor does not start, the reading will indicate the locked rotor amperage (L.R.A.). external Overload The compressor is equipped with an external overload which senses both motor amperage and winding temperature. High motor temperature or amperage heats the overload causing it to open, breaking the common circuit within the compressor. Heat generated within the compressor shell, usually due to recycling of the motor, is slow to dissipate. It may take anywhere from a few minutes to several hours for the overload to reset. Checking the external Overload WARNING ELECTRIC SHOCK HAZARD Turn off electric power before service or installation. Extreme care must be used, if it becomes necessary to work on equipmentwith power ap...
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