Non-condensables will cause which condition in a refrigeration system?

Non-condensables will cause which condition in a refrigeration system?

• A. Low discharge pressure
• B. No change
• C. Reduced compressor efficiency
• D. High discharge pressure

Answer: (D)

Non-condensables in a refrigeration system hinder heat rejection in the condenser. Air or other non-condensable gases don’t condense with the refrigerant, so they accumulate in the condenser and form a layer that slows heat transfer. To push heat out despite that resistance, the condenser pressure rises (higher head pressure). The compressor must then discharge the refrigerant at a higher pressure, so the discharge pressure increases. While reduced efficiency can accompany this condition, the direct consequence described here is the higher discharge pressure. Choices suggesting a lower or unchanged discharge pressure don’t fit because the presence of non-condensables drives the system toward higher, not lower, discharge pressure.

Non-condensables in a refrigeration system hinder heat rejection in the condenser. Air or other non-condensable gases don’t condense with the refrigerant, so they accumulate in the condenser and form a layer that slows heat transfer. To push heat out despite that resistance, the condenser pressure rises (higher head pressure). The compressor must then discharge the refrigerant at a higher pressure, so the discharge pressure increases. While reduced efficiency can accompany this condition, the direct consequence described here is the higher discharge pressure. Choices suggesting a lower or unchanged discharge pressure don’t fit because the presence of non-condensables drives the system toward higher, not lower, discharge pressure.