HVAC Sheet Metal and Fabrication 3 — Questions and Answers
Question 1: When using aviation snips to cut sheet metal, which color handle is used for straight cuts?
- Yellow (Correct answer)
- Red
- Green
- Blue
Correct answer: Yellow
Yellow-handled aviation snips are designed for straight and wide-curve cuts in sheet metal.
Question 2: What is the correct bend allowance concept used when laying out a sheet metal fitting?
- Extra material must be added to account for metal that stretches during bending (Correct answer)
- Material is removed at each bend to keep overall dimensions accurate
- Bend allowance only applies to aluminum, not galvanized steel
- The bend radius does not affect the flat pattern length
Correct answer: Extra material must be added to account for metal that stretches during bending
Bend allowance accounts for the arc length of metal at the neutral axis during bending, so extra flat length is included in the pattern.
Question 3: Which duct sealing class per SMACNA requires sealing all transverse joints, longitudinal seams, and duct wall penetrations?
- Class A (Correct answer)
- Class B
- Class C
- Class D
Correct answer: Class A
SMACNA Seal Class A requires sealing all transverse joints, longitudinal seams, and duct wall penetrations for the highest level of airtightness.
Question 4: What type of fitting connects a rectangular duct to a round duct?
- Transition fitting (Correct answer)
- Boot fitting
- Tee fitting
- Offset fitting
Correct answer: Transition fitting
A transition fitting (also called a square-to-round transition) is used to connect rectangular and round duct sections.
Question 5: In sheet metal layout, what tool is used to scribe a parallel line at a fixed distance from a straight edge?
- Dividers or a scratch awl with a straightedge (Correct answer)
- Center punch
- Combination square
- Bevel gauge
Correct answer: Dividers or a scratch awl with a straightedge
Dividers or a scratch awl guided along a straightedge are used to scribe accurate parallel layout lines on sheet metal.
Question 6: What is the minimum recommended clearance between a sheet metal duct and combustible construction according to NFPA 90A?
- 0 inches for sheet metal duct (no clearance required) (Correct answer)
- 1 inch
- 2 inches
- 6 inches
Correct answer: 0 inches for sheet metal duct (no clearance required)
NFPA 90A allows sheet metal ducts to be installed in contact with combustible construction because sheet metal itself does not ignite.
Question 7: Which type of duct configuration is most efficient for distributing air to multiple zones from a single air handler?
- Extended plenum trunk-and-branch system (Correct answer)
- Radial spider system
- Series loop system
- Single run duct system
Correct answer: Extended plenum trunk-and-branch system
An extended plenum trunk-and-branch system efficiently distributes air by maintaining relatively constant static pressure along the main trunk while branches tap off at multiple points.
HVAC Sheet Metal and Fabrication 3
When using aviation snips to cut sheet metal, which color handle is used for straight cuts?