Refrigeration Piping Do's & Don'ts


Refrigeration piping is a critical component of any refrigeration system. Whether to cut costs, because of lack of expertise, or failure to keep up with advancements in technology, inappropriate piping can cause inefficient system performance and compressor failure, and can void system warranties.

An efficient refrigeration system requires a small amount of oil to be circulated continuously with refrigerant to provide lubrication to the compressor. It is critical that refrigeration piping maintains adequate pressures and velocities so that the oil is not “lost” or trapped within the system, depriving the compressor of lubrication.

There are a number of mistakes commonly made in piping selection that can affect pressure and flow. When refrigerant piping is undersized, or if there are too many bends and fittings, pressure drops can occur. These pressure drops can result in system capacity deficit and compressor overheating. Conversely, oversized refrigeration piping does not usually affect system capacity, but causes low refrigerant velocities and poor oil return. The result: compressor failure due to lack of lubrication. Finally, if piping and line components are not properly rated, pipe work failures and splitting pipes can occur, resulting in refrigerant leaks.

Key considerations for proper refrigeration pipe selection, installation and maintenance include:

  1. Piping must adequately supply refrigerant to all evaporators while ensuring positive and continuous return of oil to the compressor.

  2. Piping must be of sufficient size to avoid refrigerant pressure losses.

  3. Liquid refrigerant must be prevented from entering the compressor during either the running or off cycles, or during compressor start-up.

  4. It is important that there is no moisture or foreign matter present. Piping must be purged with nitrogen to keep the system clean while brazing.

  5. Oil that is trapped in the evaporator or suction line can form large “slugs” that can damage the compressor. Properly sized and installed piping will prevent this.

  6. When leaks occur, they must be located and repaired promptly.

About PJM

PJM Mechanical Contractors, Inc. is a multi-faceted mechanical contractor providing construction and installation, service and maintenance, and design/build services in a comprehensive range of mechanical disciplines that include HVAC, plumbing, controls, refrigeration, custom metal fabrication, piping, fire protection, and backflow preventer testing. PJM primarily serves clients in pharmaceuticals, manufacturing, healthcare, institutional, and other various commercial and industrial sectors.

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 1688 5th Street | Ewing, NJ  08638 | Tel: 609.921.1394 | Fax: 609.530.1437

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