An inefficient compressor is usually indicated by which combination of head and suction pressures?

An inefficient compressor is usually indicated by which combination of head and suction pressures?

• A. Higher head pressure / lower suction pressure
• B. Lower head pressure / higher suction pressure
• C. Higher head pressure / higher suction pressure
• D. Lower head pressure / lower suction pressure

Answer: (B)

The key idea is how the compressor’s efficiency shows up in the pressures it has to work against. A refrigerant vapor is drawn in at the suction pressure (evaporator side) and discharged at the head or discharge pressure (condenser side). The work the compressor does rises with the pressure ratio it must produce between these two points. When the system operates with a lower discharge (head) pressure and a higher suction pressure, the pressure difference across the compressor is smaller than expected. That reduced pressure rise means the compressor isn’t moving refrigerant through the cycle as effectively as it should. In practice, this pattern often corresponds to poorer heat transfer performance and longer run times to achieve the same cooling effect, which is a hallmark of inefficiency. So, this combination is a signal that the compressor isn’t delivering the needed capacity efficiently, even if the exact causes can vary (refrigerant charge, airflow through the condenser, or other system conditions).

The key idea is how the compressor’s efficiency shows up in the pressures it has to work against. A refrigerant vapor is drawn in at the suction pressure (evaporator side) and discharged at the head or discharge pressure (condenser side). The work the compressor does rises with the pressure ratio it must produce between these two points.

When the system operates with a lower discharge (head) pressure and a higher suction pressure, the pressure difference across the compressor is smaller than expected. That reduced pressure rise means the compressor isn’t moving refrigerant through the cycle as effectively as it should. In practice, this pattern often corresponds to poorer heat transfer performance and longer run times to achieve the same cooling effect, which is a hallmark of inefficiency. So, this combination is a signal that the compressor isn’t delivering the needed capacity efficiently, even if the exact causes can vary (refrigerant charge, airflow through the condenser, or other system conditions).