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HVAC School - For Techs, By Techs

Sep 21, 2020

Joe and Eric join us, and we have a general conversation about small self-contained refrigeration units, including residential and commercial. Small refrigeration includes self-contained reach-ins and small walk-ins. These units typically use capillary tube metering devices.

Some of the biggest failures that occur in small refrigeration systems happen because of dirty condensers and user error (leaving doors open, etc.). You'll also want to check that the fans are working, the compressor is running, the coil is free of ice, and that the airflow isn't blocked. Inspection is the key, and gauging up is typically a last resort.

Refrigeration temperature measuring strategies can vary wildly by application. For example, open cases measure discharge air temperature. Systems with enclosed boxes (like walk-ins) typically sense return or box temperature. Small reach-in systems also typically have dial cold controls in a challenging location: buried at the end of the evaporator. There are straight and curly cold controls, but new equipment has made a shift towards electronic controls.

On small refrigeration units, we don't usually see start capacitors or hard start kits; however, we do see PTC relays and thermal overloads.

Domestic refrigerators also count as small refrigeration. They have independent controls that move air from the freezer to the refrigerator section of a normal household fridge; there is usually no cooling apparatus in the refrigerator. In systems with defrost timers, a bimetal defrost thermostat would open when the element detects no more ice on the coil, and defrost would terminate.

Joe, Eric, and Bryan also discuss:

  • Capillary tubes vs. other fixed-orifice metering devices
  • Capillary tube restrictions and R-134A
  • Leaky systems
  • Vacuum
  • Box temperature vs. coil temperature controllers
  • Set point and customer expectations
  • Safety controls
  • Resistance in circuits
  • Defrost fan delay and failsafe
  • Hoarfrost

Learn more about Refrigeration Technologies HERE.

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