What must be absent for the 300 psig reading?

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Multiple Choice

What must be absent for the 300 psig reading?

The key idea is that non-condensables in a refrigerant system (air or other gases that don’t condense) push the high-side pressure higher because they take up space and impede condensation. For the high-side pressure to read a specific value like 300 psig, you need a clean refrigerant charge with no non-condensables present. If non-condensables were in the system, you’d see a higher pressure than the saturated value at that temperature, not a clean 300 psig. A too-high temperature or too-small charge can affect readings too, but they don’t inherently guarantee a precise 300 psig in the same way the absence of non-condensables does.

The key idea is that non-condensables in a refrigerant system (air or other gases that don’t condense) push the high-side pressure higher because they take up space and impede condensation. For the high-side pressure to read a specific value like 300 psig, you need a clean refrigerant charge with no non-condensables present. If non-condensables were in the system, you’d see a higher pressure than the saturated value at that temperature, not a clean 300 psig. A too-high temperature or too-small charge can affect readings too, but they don’t inherently guarantee a precise 300 psig in the same way the absence of non-condensables does.

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