After the unit has run 10 to 15 minutes, check the gauge pressures.Gaugesconnectedtosystemwithanundercharge will have low head pressures and substantially low suction pressures.
Improper air fl ow over the evaporator coil may indicate some of the same symptoms as an over charged system. An overcharge can cause the compressor to fail, since it would be “slugged” with liquid refrigerant.
The charge for any system is critical. When the compressor is noisy, suspect an overcharge, when you are sure that the air quantity over the evaporator coil is correct. Icing of the evaporator will not be encountered because the refrigerant will boil later if at all. Gauges connected to system will usually have higher head pressure (depending upon amount of over charge). Suction pressure should be slightly higher.
Overcharged Refrigerant Systems
Compressor amps will be near normal or higher. Noncondensables can also cause these symptoms. To confi rm, remove some of the charge, if conditions improve, system may be overcharged. If conditions don’t improve, Noncondensables are indicated.
Wheneveranoverchargedsystemisindicated,alwaysmake sure that the problem is not caused by air fl ow problems.
Restricted Refrigerant System
Troubleshooting a restricted refrigerant system can be diffi cult. 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
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.
26