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Tech Challenge March 2023

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A logo of a yellow, red, blue, and green rubix cube with one square out of place and "Tech Challenge" written beneath it

A rooftop system utilizing R-22 with a fixed orifice metering device has a manager complaint of “no cooling.” The symptoms at the store confirm that the thermostat is not satisfied, and the condensing unit and blower are running continuously. What are the “possible causes” (there is only one problem intended) with the following measured conditions on this field service check sheet?

Field Service Check Sheet

  • Compressor Discharge Temp. 229 deg. F.
  • Condensing Press./Temp. 390 psig / 115 deg. F.
  • Condensing Outlet Temp. 87 deg. F.
  • Condenser Sub cooling 28 deg. F.
  • Condenser Split 35 deg. F.
  • Entering Feed Device Temp. 84 deg. F.
  • Evaporator Press./Temp. 129 psig / 45 deg. F.
  • Evaporator Outlet Temp. 50 deg. F.
  • Evaporator Superheat 5 deg. F.
  • Compressor Inlet Temp. 66 deg. F.
  • Total S. H. 21 Deg. F.
  • Ambient Temp. 80 deg. F.
  • Room/Box Temp. 83 deg. F.
  • Compressor Volts 240 V.
  • Compressor Amp. Draw High


Check back the first week of April for the answer!



Dick Shaw, Professor Emeritus   
Ferris State University  

Posted In: ACCA Now, Tech Challenge

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