Duct Installation Quiz: Takeoff Fittings for Sheet Metal

Questions and Answers

What standard covers ductboard and methods of connecting and sealing ductboard?

UL 181A

What is the difference between Class 0 duct and Class 1 duct?

Class 1 is better than Class 0

Class 1 - flame spread index not more than 25 and smoke developed index not more than 50 (correct)

Class 0 - flame spread index of 0 (correct)

Both are the same

Explain the difference between a flexible duct and a flexible air connector.

Flexible ducts must pass 15 tests under standard UL 181.

List the materials commonly used to construct duct systems.

Galvanized steel, fiberglass ductboard, wire-helix flexible duct. Signup and view all the answers

How is sheet-metal duct sealed?

UL-181 approved mastic and tape. Signup and view all the answers

How far apart should hangers for metal ducts be placed?

No farther than 12 feet. Signup and view all the answers

How far apart should hangers for fiber ductboard be placed?

Every 6' for ducts 12" or smaller; every 8' for ducts 12" or larger. Signup and view all the answers

List the methods of insulating metal ducts.

Duct wrap, duct liner, bubble wrap. Signup and view all the answers

List the types of takeoff fittings available for sheet metal ducts.

Flange, dove tail, sticky pad flange, folder over tabs dove tail. Signup and view all the answers

What is the correct spacing for mechanical fasteners used to hold duct liner in place?

Within 4" of the end and continued every 18". Signup and view all the answers

How does a duct blaster measure the amount of duct leakage?

Pressurizes duct system at 25 Pa to 50 Pa and required airflow to maintain pressure is obtained. Signup and view all the answers

What three methods are used to quantify duct leakage?

Percentage of design flow, airflow per 100 sq ft of conditioned area, leakage area. Signup and view all the answers

What are the two main types of duct-cleaning equipment used?

Specialized vacuum cleaner and soft bristles and brushes. Signup and view all the answers

Study Notes

Duct Installation Standards and Specifications

UL 181A covers ductboard and methods for connecting and sealing ductboard.
Class 0 ducts have a flame spread index of 0, while Class 1 ducts have a maximum flame spread index of 25 and a smoke developed index not exceeding 50.

Duct Types and Materials

Flexible ducts undergo 15 tests under standard UL 181, distinguishing them from flexible air connectors.
Common materials for duct systems include galvanized steel, fiberglass ductboard, and wire-helix flexible duct.

Sealing and Installation

Sheet-metal ducts are sealed using UL-181 approved mastic and tape.
Metal duct hangers should be placed no more than 12 feet apart.
For fiber ductboard, hangers should be spaced every 6 feet for ducts 12 inches or smaller, and every 8 feet for ducts larger than 12 inches.

Insulation Methods

Metal ducts can be insulated using duct wrap, duct liner, or bubble wrap.

Duct Fittings and Fastening

Types of takeoff fittings for sheet metal ducts include flange, dove tail, sticky pad flange, and folder over tabs dove tail.
Mechanical fasteners for duct liners should be spaced within 4 inches of the end and every 18 inches thereafter.

Duct Leakage Measurement

A duct blaster measures duct leakage by pressurizing the system at 25 Pa to 50 Pa, determining the required airflow to maintain that pressure.
Duct leakage can be quantified through three methods: percentage of design flow, airflow per 100 square feet of conditioned area, and leakage area.

Duct Cleaning Equipment

The primary types of duct-cleaning equipment are specialized vacuum cleaners and soft bristles or brushes designed for thorough cleaning.

Description

Test your knowledge on duct installation standards and methods with this comprehensive quiz based on HVACR Unit 48. Explore important differences between duct types and the relevant standards for ductboard. Perfect for HVACR students looking to solidify their understanding of duct systems.