The compressor operates continuously with which type of system controls?
a. Orifice tube
b. POA/EPR
The Correct Answer and Explanation is:
Correct Answer: a. Orifice tube
Explanation:
In automotive air conditioning systems, the type of system control used directly influences how the compressor operates—whether it runs continuously or cycles on and off. The correct answer here is “a. Orifice tube”, as systems that use an orifice tube are designed for the compressor to operate continuously.
Orifice Tube Systems:
An orifice tube is a fixed, non-adjustable device that meters the flow of refrigerant into the evaporator. These systems do not regulate the compressor operation based on temperature or pressure in the same dynamic way that POA (Pilot Operated Absolute) or EPR (Evaporator Pressure Regulator) valves do.
In orifice tube systems, a clutch cycling switch or a pressure switch is typically used to control compressor operation indirectly. However, in many modern systems that use an orifice tube and accumulator, the compressor runs continuously—especially in systems with a variable displacement compressor or an internal control valve. These setups rely on internal mechanical controls or variable displacement mechanisms rather than cycling the compressor on and off frequently. This improves system efficiency, reduces wear and tear, and provides more consistent cooling performance.
POA/EPR Systems:
POA (Pilot Operated Absolute) valves and EPR (Evaporator Pressure Regulator) valves are older technologies used primarily in expansion valve (TXV) systems. These valves maintain a constant pressure within the evaporator to prevent freeze-up and ensure consistent cooling. In these systems, the compressor may cycle on and off based on system pressure or temperature, rather than run continuously.
Summary:
- Orifice Tube Systems: Often use variable displacement compressors that run continuously.
- POA/EPR Systems: Tend to be used with cycling compressors, not continuous operation.
Thus, the compressor operates continuously with orifice tube systems, making option A the correct choice.