Other Skilled Trades Sheet Metal and HVAC 2 — Questions and Answers
Question 1: What tool is used to measure the static pressure within an HVAC duct system?
- Anemometer
- Manometer or magnehelic gauge (Correct answer)
- Multimeter
- Thermometer
Correct answer: Manometer or magnehelic gauge
A manometer or magnehelic gauge measures the static pressure (in inches of water column) within ductwork to diagnose airflow restrictions and verify system performance.
Question 2: What is the purpose of a condensate drain line on a central air conditioning system?
- To drain condensed refrigerant from the outdoor unit
- To remove water condensed from humid air on the evaporator coil (Correct answer)
- To drain the water heater
- To remove rainwater from the condenser unit
Correct answer: To remove water condensed from humid air on the evaporator coil
As warm humid air passes over the cold evaporator coil, moisture condenses and drips into a drain pan — the condensate line removes this water from the system.
Question 3: What gauge (thickness) of sheet metal is most commonly used for residential HVAC trunk ducts?
- 26 gauge
- 24 gauge (Correct answer)
- 22 gauge
- 20 gauge
Correct answer: 24 gauge
24-gauge galvanized steel is the most common thickness for residential HVAC trunk ducts, providing adequate rigidity while remaining workable for fabrication.
Question 4: What does the acronym CFM mean in HVAC?
- Central Fan Module
- Cubic Feet per Minute (Correct answer)
- Cooling Fan Mode
- Combined Flow Measurement
Correct answer: Cubic Feet per Minute
CFM (Cubic Feet per Minute) is the standard US measurement for airflow volume in HVAC systems, used to specify fan output, register sizing, and duct design.
Question 5: What is the minimum required clearance around an outdoor condenser unit for proper airflow and service access?
- 6 inches on all sides
- 12 inches on service side, 6 inches on other sides
- 18 to 24 inches on all sides (Correct answer)
- 36 inches on all sides
Correct answer: 18 to 24 inches on all sides
Most manufacturers and codes require 18–24 inches of clearance around outdoor condenser units to ensure adequate airflow for heat rejection and safe service access.
Question 6: What does a TXV (thermostatic expansion valve) do in a refrigeration system?
- Compresses the refrigerant to high pressure
- Regulates the flow of refrigerant into the evaporator based on superheat (Correct answer)
- Separates liquid and vapor refrigerant
- Measures the temperature of the refrigerant
Correct answer: Regulates the flow of refrigerant into the evaporator based on superheat
A TXV meters refrigerant flow into the evaporator coil, automatically adjusting to maintain a set superheat level and ensure the coil is fully utilized without liquid refrigerant reaching the compressor.
Other Skilled Trades Sheet Metal and HVAC 2
What tool is used to measure the static pressure within an HVAC duct system?