EPA Section 608 Universal Certification ExamType III (Low-Pressure Appliances)Medium
A technician is performing a routine maintenance check on a low-pressure chiller. They observe that the purge unit is running frequently, and there is a noticeable increase in system operating pressure. What does this indicate?
- AThe purge unit is malfunctioning and needs replacement.
- BThe condenser cooling water flow is too high.
- CThere is a leak allowing non-condensable gases to enter the system.
- DThe system is overcharged with refrigerant.
Show answer & explanationAnswer & explanation
Correct answer: C. There is a leak allowing non-condensable gases to enter the system.
Frequent operation of the purge unit and increased system pressure are classic indicators of non-condensable gases (primarily air) entering the low-pressure system. This typically happens due to a leak, as low-pressure systems operate below atmospheric pressure.
Why the other options are wrong
- A. While a purge unit can malfunction, its frequent operation *in conjunction with high pressure* suggests it's doing its job trying to remove non-condensables that are actively entering the system, implying a leak.
- B. High condenser cooling water flow would typically lead to *lower* head pressure, not higher, and would not directly cause frequent purge unit operation.
- D. Overcharging would lead to consistently high pressures and potentially liquid slugging, but not primarily cause frequent purge unit operation.
Frequent Purge Unit Operation
An indicator that non-condensable gases are entering a low-pressure refrigeration system, usually due to a leak, causing the purge unit to run excessively to maintain system efficiency.
- Low-pressure systems operate below atmospheric pressure.
- Leaks allow air (non-condensables) to enter.
- Non-condensables increase system operating pressure.
- Purge unit runs frequently to remove these gases.
Memory trick: Purge runs fast, pressure high, air is in, a leak is nigh!