HVAC Air Handler Units and Coils 2 — Questions and Answers
Question 1: What is the primary purpose of a drain pan in an air handler unit?
- To store refrigerant during servicing
- To collect condensate from the evaporator coil (Correct answer)
- To hold lubricating oil for the blower motor
- To catch debris from the air filter
Correct answer: To collect condensate from the evaporator coil
The drain pan collects condensate water that forms on the evaporator coil during the cooling process and channels it to the drain line.
Question 2: Which type of air handler configuration has the blower located downstream of the coil?
- Draw-through (Correct answer)
- Blow-through
- Vertical upflow
- Horizontal side discharge
Correct answer: Draw-through
In a draw-through configuration, the blower pulls air through the coil rather than pushing it, which is the most common arrangement.
Question 3: What causes a evaporator coil to freeze up during operation?
- Excessive refrigerant charge
- Restricted airflow or low refrigerant charge (Correct answer)
- High outdoor ambient temperature
- Oversized blower motor
Correct answer: Restricted airflow or low refrigerant charge
Restricted airflow (dirty filter, closed registers) or low refrigerant charge causes suction pressure to drop below freezing, causing the coil to ice over.
Question 4: What is the function of a TXV (thermostatic expansion valve) in relation to the evaporator coil?
- It controls airflow through the coil
- It meters refrigerant flow into the coil based on superheat (Correct answer)
- It regulates the blower motor speed
- It controls condensate drainage
Correct answer: It meters refrigerant flow into the coil based on superheat
The TXV meters refrigerant flow into the evaporator coil by sensing superheat, ensuring the coil operates efficiently without liquid refrigerant returning to the compressor.
Question 5: When installing an air handler in a vertical upflow position, where should the evaporator coil be located?
- At the top of the unit above the blower (Correct answer)
- At the bottom of the unit below the blower
- In a separate enclosure next to the blower
- On the side of the unit adjacent to the blower
Correct answer: At the top of the unit above the blower
In a vertical upflow air handler, the blower is at the bottom and the evaporator coil is at the top so air flows upward through the coil.
Question 6: What is the typical fin spacing (fins per inch) for a residential evaporator coil?
- 2-4 fins per inch
- 8-14 fins per inch (Correct answer)
- 20-25 fins per inch
- 30-40 fins per inch
Correct answer: 8-14 fins per inch
Residential evaporator coils typically have 8-14 fins per inch, balancing heat transfer efficiency with acceptable airflow resistance and ease of cleaning.
Question 7: What material are most modern evaporator coil fins made from?
- Copper
- Steel
- Aluminum (Correct answer)
- Stainless steel
Correct answer: Aluminum
Most modern evaporator coil fins are made from aluminum because it is lightweight, cost-effective, and has good thermal conductivity.
HVAC Air Handler Units and Coils 2
What is the primary purpose of a drain pan in an air handler unit?