HVAC Ductless Mini-Split Systems 2 — Questions and Answers
Question 1: What is the typical refrigerant line set length limit for most residential ductless mini-split systems without additional refrigerant charge?
- 15 feet
- 25 feet (Correct answer)
- 50 feet
- 75 feet
Correct answer: 25 feet
Most residential mini-split systems are pre-charged for approximately 25 feet of line set; longer runs require additional refrigerant.
Question 2: Which component in a ductless mini-split system is responsible for reversing refrigerant flow to switch between heating and cooling modes?
- Expansion valve
- Reversing valve (Correct answer)
- Check valve
- Solenoid valve
Correct answer: Reversing valve
The reversing (or four-way) valve redirects refrigerant flow to switch the system between heating and cooling operation.
Question 3: A mini-split indoor unit is producing a musty odor. What is the most likely cause?
- Refrigerant overcharge
- Dirty or moldy evaporator coil and drain pan (Correct answer)
- Low ambient outdoor temperature
- Incorrect refrigerant type
Correct answer: Dirty or moldy evaporator coil and drain pan
Mold and mildew growth on the evaporator coil and drain pan is the most common source of musty odors in mini-split air handlers.
Question 4: What does the SEER2 rating measure for a ductless mini-split system?
- Heating efficiency over a season
- Cooling efficiency over a cooling season (Correct answer)
- Noise level at rated capacity
- Maximum BTU output at peak load
Correct answer: Cooling efficiency over a cooling season
SEER2 (Seasonal Energy Efficiency Ratio 2) measures the cooling output divided by electrical energy input over a typical cooling season.
Question 5: When installing a mini-split indoor unit on an interior wall, what is the primary concern with the condensate drain line?
- The drain must slope upward to prevent siphoning
- The drain must slope downward at least 1/4 inch per foot to flow by gravity (Correct answer)
- Drain lines on interior walls must always use a condensate pump
- The drain line diameter must be at least 1 inch for interior walls
Correct answer: The drain must slope downward at least 1/4 inch per foot to flow by gravity
Condensate must drain by gravity, requiring a continuous downward slope of at least 1/4 inch per foot to prevent water backup and overflow.
Question 6: What happens to a ductless mini-split system's heating capacity as outdoor temperature drops significantly below its rated condition?
- Heating capacity remains constant regardless of outdoor temperature
- Heating capacity increases as outdoor temperature drops
- Heating capacity decreases as outdoor temperature drops (Correct answer)
- The system automatically switches to emergency heat coils
Correct answer: Heating capacity decreases as outdoor temperature drops
As outdoor temperature drops, there is less heat energy available in the outdoor air for the heat pump to extract, reducing heating capacity.
Question 7: Which type of ductless mini-split installation requires penetrating the building envelope for refrigerant line sets?
- Concealed duct type only
- All mini-split types except window units
- Cassette type only
- All ductless mini-split configurations (Correct answer)
Correct answer: All ductless mini-split configurations
All ductless mini-split systems require refrigerant line sets connecting indoor and outdoor units, which must pass through the building envelope.
HVAC Ductless Mini-Split Systems 2
What is the typical refrigerant line set length limit for most residential ductless mini-split systems without additional refrigerant charge?