The purpose of a direct expansion, or DX, system is to remove unwanted heat from a space or substance and transfer it to another space or substance. DX refrigeration systems are sometimes called mechanical refrigeration systems because they use mechanical components to remove and transfer heat. They are widely used in refrigerators, freezers, split systems, and package AC or rooftop units (RTUs). When troubleshooting a DX system, check the basics first – superheat in the suction line, subcooling in the liquid line, suction pressure, discharge (or head) pressure, and motor amps – to see if they are in their normal ranges for current conditions. A troubleshooting chart appropriate for your expansion device can provide guidance as to the possible issues. If you can’t pinpoint the problem, there may be an issue with one of the mechanical components. This course covers component issues that can affect the performance of a DX system, including issues with the compressor, compressor motor, expansion valve, refrigerant charge, liquid line, and lubricating oil system. This information, plus experience working around DX systems, will help you troubleshoot problems successfully and in a timely manner.
