In consulting the R-134a pressure-temperature...

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Question 1 of 205eccef9dbacbc34ba4d45e5c

In consulting the R-134a pressure-temperature chart shown in the illustration, what would be the most likely normal running suction pressure for a reach-in chill box, assuming the box temperature is within normal range? See illustration GS-RA-11.

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🔍 Key Concepts

• Use the R-134a pressure–temperature chart to match a saturation pressure with a likely evaporator temperature. • A reach-in chill box (not a freezer) normally operates a little above the freezing point of water; the evaporator coil runs colder than the box air. • Suction pressure on a running system with a TXV/Cap tube will usually be close to the saturation pressure at the evaporator temperature.

💭 Think About

• First, decide what a normal box air temperature range would be for a reach-in chill box in good condition. • Then estimate how much colder the evaporator coil must be than the box air (typical temperature difference) to absorb heat efficiently. • Using that coil (evaporator) temperature, locate the corresponding psig on the R‑134a chart and compare it with the choices given.

✅ Before You Answer

• Verify that you are reading from the pressure (psig) column, not the vacuum column, for the temperature you chose. • Check that the temperature you use is a realistic evaporator temperature (a bit below desired box temperature, but not a freezer value). • Confirm that the option you select lines up closely with the interpolated pressure for that evaporator temperature on the chart.

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