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HVAC School - For Techs, By Techs

Feb 24, 2022

Brett Wetzel and Kevin Compass from the Advanced Refrigeration Podcast join us to discuss commercial rack refrigeration and identify components.

In supermarket racks, we typically have anywhere from 2-5 compressors on a single rack (with multiple evaporators, metering devices, and sometimes even condensers). These compressors may come in several varieties (including screw and scroll) and be digital or have VFDs. They also have common suction and discharge headers. 

The compressors all share oil from a single system. Oil separators can come in three varieties: centrifugal, impingement, and coalescing (most efficient). The separator would feed into the reservoir, which stores oil. 

Many rack systems use several different valves. Check valves to direct the refrigerant flow, especially on heat reclaim systems and split condensers. In some cases, there is a three-way valve or a solenoid valve that controls or stops the refrigerant flow. LDR (liquid differential regulating) valves maintain the required differentials during defrost. Ball valves can be found all over a rack (liquid line, suction line, discharge line, etc.) and can isolate a line. Standard and balanced-port TXVs or EEVs may also appear on racks. There is also an EPR, which controls evaporator temperature and pressure.

Grocery systems have a drop leg before the receiver, which stores liquid refrigerant. We want a full column of liquid leaving the receiver, which we can confirm with a sight glass rather than subcooling.

Brett, Kevin, and Bryan also discuss:

  • Reheat and excess heat
  • Split condensers
  • Drain leg/drop leg vs. liquid line
  • Mechanical subcooling and heat exchangers
  • Counterflow piping
  • Hot gas vs. Kool gas defrost
  • Standard vs. balanced-port TXVs
  • Distributors
  • Evaporator fin spacing
  • Cleaning components


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