HVAC - EPA Certification Practice Exam

What effect does a high concentration of non-condensables have on system performance?

1. It lowers refrigerant pressure

2. It causes higher discharge pressures

3. It improves heat exchange

4. It enhances energy efficiency

The correct answer is: It causes higher discharge pressures

A high concentration of non-condensables in an HVAC system can significantly impact system performance by causing higher discharge pressures. Non-condensables, such as air or other gases that do not condense at the operating temperatures and pressures of the refrigerant, accumulate in the condenser. Since these gases do not undergo phase changes like the refrigerant does, they occupy space in the condenser where the refrigerant should condense. This leads to an increase in overall pressure within the system, specifically the discharge pressure. The elevated discharge pressure can result in several issues, including increased compressor workload and decreased overall efficiency of the cooling cycle. The higher pressure reduces the effective cooling capacity of the system, leading to reduced performance. Moreover, the compressor must work harder to compress the refrigerant to these higher pressures, which may lead to accelerated wear and potential system failure if the condition persists. Understanding the behavior and impact of non-condensables on system performance is crucial for maintaining efficiency and longevity in HVAC systems.