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HVAC School - For Techs, By Techs

Aug 27, 2020

Our good friend Trevor Matthews from Emerson Canada joins us to talk about compressors, mostly preventing compressor failure and troubleshooting issues.

Whenever we're installing or servicing a compressor, we need to think about possible systemic issues right off the bat. The compressor is the heart of the system, but everything else in the system affects how the compressor runs. You'll want to know which type of compressor you're working with as well as the manufacturer. As always, you'll want to check the superheat, subcooling, amps, TD across the condenser, and (especially) discharge line temperature.

The compression ratio is also a telling sign of the system and compressor's health. You take the compression ratio by dividing the absolute suction pressure into the absolute discharge pressure. However, we must also consider the compressor's application; by design, refrigeration compressors can deal with higher head pressures than A/C compressors.

Anytime a compressor fails, you'll want to investigate why it failed. You can only see what happened inside a compressor if you cut it open and inspect it. During the inspection, look for signs of overheating and damaged components. Whether a burnout, flooded start, or thermal overload caused the failure, you will be able to see clues about the failure and can piece together the compressor's story. Once we finish troubleshooting and diagnosing a compressor, we can focus on preventing future compressor failure. We'll have a better idea of the operating conditions we need to avoid.

Trevor and Bryan also discuss:

  • Head pressure (discharge pressure vs. liquid line pressure)
  • Compressor types
  • Compressor overheating
  • Return gas temperature
  • Burnout
  • Line driers
  • The 80/20 rule
  • Flooded starts
  • Short cycling
  • Non-bleed TXVs
  • Recovery and evacuation
  • Thermal limit
  • Advanced temperature scroll protector (ATSP)

Emerson Flow Chart -

Compressor Installation Guide -

Emerson System Cleanup Bulletin -

Learn more about Refrigeration Technologies HERE.

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