Air Conditioning Repair Installation and Evacuation Procedures 4 — Questions and Answers
Question 1: A dual-stage vacuum pump should have its oil changed:
- After each use or when the oil appears dark and contaminated (Correct answer)
- Only when the pump fails to reach target vacuum
- Once per year regardless of use
- Every 500 operating hours only
Correct answer: After each use or when the oil appears dark and contaminated
Vacuum pump oil absorbs moisture during system evacuation and should be changed after every use to maintain the pump's ability to achieve deep vacuums.
Question 2: What is the correct refrigerant line sizing rule regarding the suction line versus the liquid line?
- The suction line is always larger in diameter than the liquid line (Correct answer)
- Both lines are always the same diameter
- The liquid line is always larger than the suction line
- Line diameter depends only on refrigerant type, not pressure side
Correct answer: The suction line is always larger in diameter than the liquid line
Suction line carries low-pressure vapor (low density) and must be larger diameter than the liquid line to maintain proper refrigerant velocity and oil return.
Question 3: When an AC outdoor unit is installed on a rooftop, the mounting platform must:
- Be structurally rated for the unit weight and allow for vibration isolation (Correct answer)
- Be constructed of wood for flexibility
- Be elevated exactly 12 inches above the roof surface
- Be secured with standard wood screws only
Correct answer: Be structurally rated for the unit weight and allow for vibration isolation
Rooftop installations require structurally adequate, properly rated supports with vibration isolation pads to protect both the unit and the roof structure.
Question 4: Which EPA regulation governs the handling and recovery of refrigerants during AC service and installation?
- Section 608 of the Clean Air Act (Correct answer)
- OSHA 1910.119
- Section 407 of the Energy Policy Act
- ASHRAE Standard 90.1
Correct answer: Section 608 of the Clean Air Act
EPA Section 608 prohibits venting refrigerants and requires certified technicians to use approved recovery equipment during service, maintenance, and installation.
Question 5: What is 'triple evacuation' (also called 'three-step evacuation') used for?
- Removing moisture more effectively by breaking vacuum with dry nitrogen between pulls (Correct answer)
- Charging the system in three stages to prevent slugging
- Testing system performance at three different load conditions
- Evacuating three separate refrigerant circuits simultaneously
Correct answer: Removing moisture more effectively by breaking vacuum with dry nitrogen between pulls
Triple evacuation involves pulling vacuum, breaking with dry nitrogen, then repeating twice more — each cycle draws out more moisture than a single long pull.
Question 6: The condensate drain line for a horizontal air handler installed in an attic should include:
- A secondary drain pan with a separate overflow drain or safety switch (Correct answer)
- Only the primary drain — secondary systems are optional
- A check valve to prevent backflow
- A UV light to sterilize condensate
Correct answer: A secondary drain pan with a separate overflow drain or safety switch
Attic-installed air handlers require a secondary condensate pan with drain or float switch to prevent ceiling water damage if the primary drain clogs.
Question 7: When installing a ductless mini-split, the wall sleeve (line set hole) should be drilled at a slight downward angle toward the outside to:
- Allow condensate from the wall sleeve area to drain outdoors (Correct answer)
- Improve refrigerant flow velocity
- Reduce vibration transmission into the wall
- Allow easier electrical wire routing
Correct answer: Allow condensate from the wall sleeve area to drain outdoors
A slight downward pitch toward the exterior ensures any water that enters the wall sleeve hole drains outward rather than into the structure.
Air Conditioning Repair Installation and Evacuation Procedures 4
A dual-stage vacuum pump should have its oil changed: