HVAC Sheet Metal and Fabrication 5

Question 1

What is the primary reason galvanized steel is the most common material for HVAC ductwork?

Accepted Answer

It provides corrosion resistance without requiring additional coatings

Answer

The zinc coating on galvanized steel provides inherent corrosion resistance, making it durable and cost-effective for most HVAC duct applications.

Question 2

Which fitting is used to offset duct around an obstruction while maintaining the same duct size?

Accepted Answer

Offset fitting

Answer

An offset fitting shifts the duct laterally or vertically to route around a beam, pipe, or other obstruction while keeping the same duct dimensions.

Question 3

When a wye fitting splits a round duct into two branches, what should the combined cross-sectional area of the branches equal for proper air distribution?

Accepted Answer

Approximately equal to or greater than the main trunk area

Answer

The combined area of the two branches should at least equal the main trunk area to avoid excessive velocity increase and pressure loss at the split.

Question 4

What type of mastic sealant is recommended for sealing HVAC duct joints in unconditioned spaces?

Accepted Answer

UL 181-listed water-based duct mastic applied with mesh tape

Answer

UL 181-listed duct mastic reinforced with fiberglass mesh tape provides a durable, airtight seal that remains flexible across temperature cycles in unconditioned spaces.

Question 5

What is 'parallel pattern development' used for in HVAC sheet metal layout?

Accepted Answer

Developing the flat pattern of cylinders and prisms that have parallel lateral edges

Answer

Parallel pattern development (parallel line development) is used to unfold fittings such as cylinders, rectangular ducts, and elbows whose lateral edges are parallel.

HVAC Practice Test

HVAC Practice Test

HVAC Sheet Metal and Fabrication 5