313A System Troubleshooting & Safety 2 — Questions and Answers
Question 1: What does the CSA B52 Mechanical Refrigeration Code govern in Canada?
- The transportation of refrigerant cylinders by road and rail
- The design, construction, installation, and testing of refrigeration and air conditioning systems in Canada (Correct answer)
- The certification requirements for refrigeration technicians
- The performance testing of residential air conditioners for ENERGY STAR rating
Correct answer: The design, construction, installation, and testing of refrigeration and air conditioning systems in Canada
CSA B52 is the Canadian standard that governs the design, construction, installation, testing, and maintenance of mechanical refrigeration systems, and it is adopted by provincial codes across Canada.
Question 2: What is a 'pressure test' as performed under CSA B52 after installing a new refrigeration system?
- Pressurizing the system with refrigerant to operating pressure to check for leaks
- Pressurizing the system with dry nitrogen to the test pressure specified in CSA B52 to verify the integrity of the refrigerant circuit before introducing refrigerant (Correct answer)
- Testing the relief valve by manually lifting it at operating pressure
- Measuring suction and discharge pressures with a manifold gauge after startup
Correct answer: Pressurizing the system with dry nitrogen to the test pressure specified in CSA B52 to verify the integrity of the refrigerant circuit before introducing refrigerant
CSA B52 requires a pressure test using dry nitrogen (never oxygen or refrigerant alone) to a specified test pressure before refrigerant is introduced, verifying that all joints, fittings, and components are leak-free and structurally sound.
Question 3: What does an electronic leak detector indicate when it sounds an alarm near a refrigerant line?
- Presence of moisture in the refrigerant circuit
- Detection of refrigerant vapour concentration above the instrument's threshold at that location (Correct answer)
- Electrical fault in the refrigerant circuit wiring
- High refrigerant velocity in the pipe indicating a restriction
Correct answer: Detection of refrigerant vapour concentration above the instrument's threshold at that location
An electronic leak detector senses refrigerant vapour concentration and alarms when it exceeds the instrument's sensitivity threshold, indicating a likely leak source that the technician should confirm and repair.
Question 4: What is the recommended method to confirm a refrigerant leak location after an electronic detector gives an alarm?
- Open the system immediately and visually inspect all joints
- Apply an approved refrigerant-compatible leak detection solution (bubble solution) or use a UV dye and UV light to pinpoint the exact leak location (Correct answer)
- Pressurize the system above normal operating pressure to make the leak larger and easier to find
- Replace all brazed joints in the area indicated by the detector
Correct answer: Apply an approved refrigerant-compatible leak detection solution (bubble solution) or use a UV dye and UV light to pinpoint the exact leak location
After an electronic detector alerts to a possible leak, bubble solution or UV dye with a UV lamp is used to pinpoint the exact location; UV dye that was pre-charged into the system glows brightly at the leak site under UV light.
Question 5: Why must oxygen (O2) never be used to pressure test a refrigeration system?
- Oxygen reacts with refrigerant oils to form an explosive mixture that can detonate under pressure (Correct answer)
- Oxygen dissolves into the refrigerant and changes its thermodynamic properties
- Oxygen is too expensive for routine use as a test gas
- Oxygen is a non-condensable that is difficult to purge from the system after testing
Correct answer: Oxygen reacts with refrigerant oils to form an explosive mixture that can detonate under pressure
Oxygen mixed with refrigerant oil vapour under pressure creates a potentially explosive mixture — this hazard has caused fatal accidents, and all codes absolutely prohibit using oxygen or air to pressure test refrigeration systems.
Question 6: What is the purpose of a relief valve on a refrigeration pressure vessel under CSA B52?
- To release refrigerant to the atmosphere to reduce system charge during overcharge conditions
- To automatically vent refrigerant if internal pressure exceeds a safe limit, preventing catastrophic vessel rupture (Correct answer)
- To manually release pressure before opening the system for service
- To balance pressure between the high and low sides of the system during shutdown
Correct answer: To automatically vent refrigerant if internal pressure exceeds a safe limit, preventing catastrophic vessel rupture
A relief valve is a code-required safety device that automatically opens to release refrigerant when vessel pressure exceeds the design limit, preventing a potentially catastrophic mechanical failure of the pressure vessel.
313A System Troubleshooting & Safety 2
What does the CSA B52 Mechanical Refrigeration Code govern in Canada?