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Questions and Answers
What is the highest permissible continuous operating temperature within a fibrous glass duct?
What is the highest permissible continuous operating temperature within a fibrous glass duct?
- 225°F
- 200°F
- 275°F
- 250°F (correct)
In the absence of staple flaps to temporarily secure seams and joints on fibrous glass ducts, which alternative method is recommended prior to applying the final closure system?
In the absence of staple flaps to temporarily secure seams and joints on fibrous glass ducts, which alternative method is recommended prior to applying the final closure system?
- Cross tabs made of closure tape (correct)
- Hot seal tape
- Pressure seal tape
- Overlapping tabs of duct board
What is the minimum length requirement for sheet metal screws used to penetrate fibrous glass duct board?
What is the minimum length requirement for sheet metal screws used to penetrate fibrous glass duct board?
- No less than 1.25 inches long
- 0.5 inch (12.7 mm) longer than the board thickness (correct)
- 1 inch longer than the board thickness
- 7/8 inches longer than the board thickness
When employing cross tabs on fibrous glass duct seams and joints lacking staple flaps, what is the minimum recommended length for each cross tab?
When employing cross tabs on fibrous glass duct seams and joints lacking staple flaps, what is the minimum recommended length for each cross tab?
A duct constructed of 1-inch thick fibrous glass duct board that is 60 inches wide shall be supported by hangers a maximum of how many feet on center?
A duct constructed of 1-inch thick fibrous glass duct board that is 60 inches wide shall be supported by hangers a maximum of how many feet on center?
What is the maximum permissible spacing between hangers supporting fibrous glass ductwork that measures 48 inches or greater in width?
What is the maximum permissible spacing between hangers supporting fibrous glass ductwork that measures 48 inches or greater in width?
What gauge of sheet metal is required to support 20" x 12" diffuser connections in fibrous glass ductwork with a bearing plate?
What gauge of sheet metal is required to support 20" x 12" diffuser connections in fibrous glass ductwork with a bearing plate?
Under what maximum width condition can 22-gauge, 2" x 1.5" hangers be used in place of standard 3-inch duct hangers for fibrous duct board?
Under what maximum width condition can 22-gauge, 2" x 1.5" hangers be used in place of standard 3-inch duct hangers for fibrous duct board?
What is the minimum width requirement for all heat seal tapes used in the construction of fibrous glass duct systems?
What is the minimum width requirement for all heat seal tapes used in the construction of fibrous glass duct systems?
A 30" x 30" fibrous glass duct shall be supported by hangers a maximum of how many feet on center?
A 30" x 30" fibrous glass duct shall be supported by hangers a maximum of how many feet on center?
Which closure system is deemed unsuitable for rigid fibrous glass duct systems due to non-compliance with UL 181 or UL 181A standards?
Which closure system is deemed unsuitable for rigid fibrous glass duct systems due to non-compliance with UL 181 or UL 181A standards?
It is recommended that fibrous glass duct systems (when used in air conditioning systems) not exceed what pressure in inches W.G.?
It is recommended that fibrous glass duct systems (when used in air conditioning systems) not exceed what pressure in inches W.G.?
A 48" x 48" duct constructed of 1-inch thick duct board shall be supported by hangers at a maximum interval of how many feet on center?
A 48" x 48" duct constructed of 1-inch thick duct board shall be supported by hangers at a maximum interval of how many feet on center?
What is the minimum size hanger wire gauge recommended for fibrous glass duct?
What is the minimum size hanger wire gauge recommended for fibrous glass duct?
For what application is fibrous glass duct suitable?
For what application is fibrous glass duct suitable?
What size and type of screws are required for Z-framing around the opening of a flange, spaced 6 inches on center?
What size and type of screws are required for Z-framing around the opening of a flange, spaced 6 inches on center?
A fibrous glass duct measures 36 inches by 64 inches. What is the maximum allowable spacing, in feet, for supporting this straight duct?
A fibrous glass duct measures 36 inches by 64 inches. What is the maximum allowable spacing, in feet, for supporting this straight duct?
For a 1-inch water gauge utilizing Type 475 board with an inside duct dimension of 22 inches, what tie rod reinforcement spacing is required?
For a 1-inch water gauge utilizing Type 475 board with an inside duct dimension of 22 inches, what tie rod reinforcement spacing is required?
When staple flaps aren't used to join seams and joints, cross tabs must be equally spaced on each side of the joint and on what maximum centers?
When staple flaps aren't used to join seams and joints, cross tabs must be equally spaced on each side of the joint and on what maximum centers?
A straight piece of fibrous glass duct with a three-inch-wide channel measures 36 inches high and 60 inches wide inside. What is the maximum allowable hanger spacing for this ductwork in feet?
A straight piece of fibrous glass duct with a three-inch-wide channel measures 36 inches high and 60 inches wide inside. What is the maximum allowable hanger spacing for this ductwork in feet?
What is the minimum number of pieces required to construct a 45-degree fibrous glass duct elbow?
What is the minimum number of pieces required to construct a 45-degree fibrous glass duct elbow?
Cross tabs holding seams and joints in place before closure are made from closure tape lengths of at least how many inches?
Cross tabs holding seams and joints in place before closure are made from closure tape lengths of at least how many inches?
A contractor is installing a 12-inch wide flanged electric heater in a 12-inch by 18-inch fibrous glass duct. Given the need for sheet metal to safely mount the heater, what is the MOST appropriate quantity and gauge of sheet metal required?
A contractor is installing a 12-inch wide flanged electric heater in a 12-inch by 18-inch fibrous glass duct. Given the need for sheet metal to safely mount the heater, what is the MOST appropriate quantity and gauge of sheet metal required?
For a 24-inch by 24-inch fibrous glass duct, utilizing 3-inch-wide channel for hanger support, what is the MAXIMUM permissible spacing, in feet, between hangers to ensure structural integrity and compliance with standard practices?
For a 24-inch by 24-inch fibrous glass duct, utilizing 3-inch-wide channel for hanger support, what is the MAXIMUM permissible spacing, in feet, between hangers to ensure structural integrity and compliance with standard practices?
When installing volume dampers in fibrous glass duct, what is the MOST critical requirement to prevent damage and maintain the duct's integrity?
When installing volume dampers in fibrous glass duct, what is the MOST critical requirement to prevent damage and maintain the duct's integrity?
According to UL181 A standards, listed enclosures MUST utilize specific materials for secure sealing. Which of the following sealing methods is NOT typically approved under these standards?
According to UL181 A standards, listed enclosures MUST utilize specific materials for secure sealing. Which of the following sealing methods is NOT typically approved under these standards?
What is the MINIMUM acceptable width, in inches, for pressure-sensitive tape used in sealing fibrous glass ductwork to ensure adequate adhesion and prevent air leakage?
What is the MINIMUM acceptable width, in inches, for pressure-sensitive tape used in sealing fibrous glass ductwork to ensure adequate adhesion and prevent air leakage?
When incorporating sheet metal sleeves inside ductboard for electric heater applications, how far, in inches, MUST the sleeves extend beyond each side of the heater to provide adequate heat protection and prevent damage to the ductboard?
When incorporating sheet metal sleeves inside ductboard for electric heater applications, how far, in inches, MUST the sleeves extend beyond each side of the heater to provide adequate heat protection and prevent damage to the ductboard?
When securing ductboard with screws, what is the MAXIMUM permissible length, in inches, by which the screws can exceed the thickness of the ductboard to prevent compromising the duct's integrity?
When securing ductboard with screws, what is the MAXIMUM permissible length, in inches, by which the screws can exceed the thickness of the ductboard to prevent compromising the duct's integrity?
Under what conditions is fibrous glass duct board MOST appropriately used, considering its limitations in withstanding pressure and exposure to certain substances?
Under what conditions is fibrous glass duct board MOST appropriately used, considering its limitations in withstanding pressure and exposure to certain substances?
What type of lock is commonly used for straight duct and fittings?
What type of lock is commonly used for straight duct and fittings?
What is the maximum distance screws can be spaced apart on duct access panels?
What is the maximum distance screws can be spaced apart on duct access panels?
For rectangular ducts with flexible liners and an interior width of 6 inches, what is the requirement regarding mechanical fasteners?
For rectangular ducts with flexible liners and an interior width of 6 inches, what is the requirement regarding mechanical fasteners?
What is the requirement for devices installed inside lined ducts or fittings?
What is the requirement for devices installed inside lined ducts or fittings?
According to regulations, what entity sets the standards for belt guards?
According to regulations, what entity sets the standards for belt guards?
What component is represented by the drawing resembling a branching duct?
What component is represented by the drawing resembling a branching duct?
What type of steel sheet is required for ducts and connectors unless otherwise specified?
What type of steel sheet is required for ducts and connectors unless otherwise specified?
The Type L-2 longitudinal duct seam is suitable for use up to what static pressure?
The Type L-2 longitudinal duct seam is suitable for use up to what static pressure?
What is the operating pressure range required for one-inch wg.?
What is the operating pressure range required for one-inch wg.?
How often should longitudinal standing seams be fastened on ducts?
How often should longitudinal standing seams be fastened on ducts?
What material is acceptable for reinforcement for flat sides of oval duct?
What material is acceptable for reinforcement for flat sides of oval duct?
What is the minimum gage requirement for duct access panels?
What is the minimum gage requirement for duct access panels?
What is the maximum allowable sag between supports for flexible duct?
What is the maximum allowable sag between supports for flexible duct?
Class C transverse joints are applicable for a static pressure construction class up to what level?
Class C transverse joints are applicable for a static pressure construction class up to what level?
For ducts using adhesive, what interior width allows skipping mechanical fasteners?
For ducts using adhesive, what interior width allows skipping mechanical fasteners?
What type of lock system is best suited for straight duct and fittings?
What type of lock system is best suited for straight duct and fittings?
Which of the following is a factor to consider when determining duct dimensions?
Which of the following is a factor to consider when determining duct dimensions?
What is a primary purpose of applying adhesive to ductwork?
What is a primary purpose of applying adhesive to ductwork?
Which of the following best describes a low-pressure duct system?
Which of the following best describes a low-pressure duct system?
Which of the following is a common type of seam used in ductwork?
Which of the following is a common type of seam used in ductwork?
What does the term 'W.G.' typically stand for in the context of duct pressure?
What does the term 'W.G.' typically stand for in the context of duct pressure?
Which of the following should be considered during duct installation?
Which of the following should be considered during duct installation?
What is the purpose of using joint reinforcement in ductwork?
What is the purpose of using joint reinforcement in ductwork?
Why is proper sealing important for ductwork?
Why is proper sealing important for ductwork?
Flashcards
Max temp in fibrous glass duct?
Max temp in fibrous glass duct?
250°F
Missing staple flaps?
Missing staple flaps?
Crosstabs
Screw length penetrating duct board?
Screw length penetrating duct board?
0.5 inch (12.7 mm) longer than the board thickness
Minimum cross tab length (inches)?
Minimum cross tab length (inches)?
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Max hanger spacing for >48 inch duct?
Max hanger spacing for >48 inch duct?
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Max width (in) for 22-gage hangers?
Max width (in) for 22-gage hangers?
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Minimum width of heat seal tapes (inches)?
Minimum width of heat seal tapes (inches)?
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Unsuitable closure System?
Unsuitable closure System?
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Sheet Metal Needed for Heater
Sheet Metal Needed for Heater
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Fibrous Glass Duct Hanger Spacing
Fibrous Glass Duct Hanger Spacing
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Volume Dampers in Fibrous Glass Duct
Volume Dampers in Fibrous Glass Duct
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UL181 A Listed Enclosures
UL181 A Listed Enclosures
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Pressure Sensitive Tape Width
Pressure Sensitive Tape Width
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Sheet Metal Sleeves for Ductboard Heaters
Sheet Metal Sleeves for Ductboard Heaters
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Screw Length for Ductboard
Screw Length for Ductboard
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Fibrous Glass Duct Board Use
Fibrous Glass Duct Board Use
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Z-framing screw spec.
Z-framing screw spec.
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Max spacing: 36" x 64" duct
Max spacing: 36" x 64" duct
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Tie rod reinforcement?
Tie rod reinforcement?
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Max spacing: 44" x 56" duct
Max spacing: 44" x 56" duct
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Cross tab spacing
Cross tab spacing
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Max hanger spacing
Max hanger spacing
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Min pieces: 45° elbow
Min pieces: 45° elbow
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Cross tab tape length
Cross tab tape length
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Fibrous Glass Duct Support Spacing (60" wide)
Fibrous Glass Duct Support Spacing (60" wide)
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Diffuser Connection Support
Diffuser Connection Support
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Fibrous Glass Duct Support Spacing (30"x30")
Fibrous Glass Duct Support Spacing (30"x30")
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Max Pressure for Fibrous Glass Duct
Max Pressure for Fibrous Glass Duct
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Fibrous Glass Duct Support Spacing (48"x48")
Fibrous Glass Duct Support Spacing (48"x48")
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Minimum Hanger Wire Gage
Minimum Hanger Wire Gage
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Fibrous Glass Duct Temperature Range
Fibrous Glass Duct Temperature Range
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Heater Support Dimensions
Heater Support Dimensions
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Flat drive slip T-1 use
Flat drive slip T-1 use
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Max spacing: duct access panel screws
Max spacing: duct access panel screws
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Devices inside lined ducts
Devices inside lined ducts
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Steel sheet coating standard
Steel sheet coating standard
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Longitudinal duct seam Type L-2
Longitudinal duct seam Type L-2
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Duct seam fastening intervals
Duct seam fastening intervals
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Duct access panel gage
Duct access panel gage
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Duct width without mechanical fasteners
Duct width without mechanical fasteners
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Pittsburgh lock
Pittsburgh lock
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Ducts w/ Flexible Liners (6-inch width)
Ducts w/ Flexible Liners (6-inch width)
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Belt Guard Regulations
Belt Guard Regulations
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Volume damper
Volume damper
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1-inch wg. Operating Pressure
1-inch wg. Operating Pressure
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Oval Duct Reinforcement
Oval Duct Reinforcement
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Max Sag: Flexible Duct
Max Sag: Flexible Duct
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Class C Transverse Joints
Class C Transverse Joints
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SMACNA Duct Standards
SMACNA Duct Standards
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Using SMACNA Tables
Using SMACNA Tables
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Weight Per Foot (WPF)
Weight Per Foot (WPF)
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Volume Damper Material
Volume Damper Material
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UL181 A Enclosures
UL181 A Enclosures
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Unsuitable Tape
Unsuitable Tape
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Fibrous Glass Duct Use
Fibrous Glass Duct Use
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60" Duct Hanger Spacing
60" Duct Hanger Spacing
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Study Notes
- Fibrous Glass Duct Construction Standards based on SMACNA, 7th and 8th Editions.
Temperature
- The maximum temperature inside a fibrous glass duct with continuous operation is 250°F.
Closure Systems
- Pressure seal tape should be used when staple flaps are not present to hold seams and joints in place before applying the closure system.
- A closure system that does not comply with UL 181 or UL 181A is not suitable for rigid fibrous glass duct systems.
- Mastic-pressured glycol tape is not suitable for use with rigid fibrous glass duct systems and does not comply with UL 181 or UL 181A.
Sheet Metal Screws
- All sheet metal screws penetrating duct board shall be 0.5 inch (12.7 mm) longer than the board thickness.
Cross Tabs
- When staple flaps are not present, cross tabs are to be equally spaced on each side of the joint and made from 8 inch minimum lengths of closure tape.
- For seams and joints without staple flaps, cross tabs made from 8-inch minimum lengths of closure tape should be used.
- The cross tabs should be spaced equally on each side of the joint and on 12-inch centers with at least one cross tab per duct side.
- When staple flaps are not used to join seams and joints, cross tabs must be equally spaced on each side of the joint and on 12 inch maximum centers.
- When staple flaps are not used to join seams and joints there must be at least one cross tab per duct side
- Cross tabs used to hold seams and joints in place prior to the application of a closure system must be made from lengths of closure tape at least 8 inches long.
Hangers
- For fibrous duct board, 22 gage, 2" x 1.5" hangers may substitute for 3 inches duct hangers with widths not over 48 inches.
- The maximum hanger spacing for duct 48 inches or greater is 4 feet.
- Fibrous glass duct 24 inches by 24 inches using 3-inch-wide channel requires hanger spacing at no more than 6 feet maximum.
- The fibrous glass duct is 36 inches by 64 inches and the maximum allowable spacing for the straight duct is 4 feet.
- The fibrous glass duct measures 44 inches by 56 inches and the maximum allowable spacing for the straight duct is 4 feet.
- A piece of fibrous glass duct is straight with a three-inch-wide channel, is 36 inches high and 60 inches wide inside and the maximum allowable hanger spacing for this ductwork is 4 feet.
- A duct constructed of 1-inch thick fibrous glass duct board that is 60 inches wide shall be supported by hangers a maximum of 4 feet on center.
- A 30" x 30" fibrous glass duct shall be supported by hangers a maximum of 4 feet on center.
- A 48" x 48" duct constructed of 1-inch thick duct board shall be supported by hangers a maximum of 4 feet on center.
Fastening
- Z-framing around the opening of a flange on opening requires #10 x 1.25 inch sheet metal screws 6 inches on center.
Tie Rods
- The water gage is 1 inch given the contractor installing Type 475 Board. The inside duct dimension is 22 and the tie rod reinforcement is not required.
- If the access door width interferes with reinforcement, install the tie rods 4 inches from each side of the door opening.
Duct Elbows
- A 45-degree fibrous glass duct elbow requires a minimum of 2 pieces.
- A 90-degree fibrous glass duct elbow requires a minimum of 3 pieces.
Tape Measurements
- All heat seal tapes shall be a minimum width of 3 inches.
- All pressure sensitive tape shall be a minimum width of 2.5 inches.
- The minimum overhang for a seam without staple flaps when using pressure sensitive tape is 1.25 inch(es).
- Closure tape should be centered over edge of stapling flap 1 inch(es) minimum overlap.
Heater Installation
- When installing a flanged or slip-in electric heater in the duct, where the heater is 12 inches wide and being installed in a fibrous glass duct 12 inches by 18 inches, 10 square feet of 22 gage sheet metal will be needed.
- Sheet metal sleeves used inside ductboard for heater applications shall extend 6 inches beyond each side of the heater.
Ductboard
- All screws penetrating ductboard shall be no more than 0.5 inches longer than the ductboard.
- 20" x 12"" diffuser connections in fibrous glass ductwork are to be supported by a bearing plate of 22 gage sheet metal.
Usage
- Fibrous glass duct board may be used for supply air ductwork subject to 2-inch WG static pressure.
- It is recommended that fibrous glass duct systems when used in air conditioning systems, not exceed 2 inches W.G.
- Fibrous glass duct may be used for conveying air at 40°F to 250°F (4.4°C to 121.1°C).
Other Requirements
- UL181 A requires listed enclosures be any of the following except heat activated aluminum foil tapes.
- Volume dampers in fibrous glass duct require metal sleeves.
- The length of duct board (1-inch thick) required to fabricate a duct 40 inches wide x 16 inches high is 10 feet, assuming a flap width of 1-3/8 inches is included.
- A 44" x 40" fibrous glass duct operating at 1/2-inch WG static pressure may be reinforced with a 22 gage 1.25" x 1.25" tee.
- The collar of a 20" by 12" diffuser connection shall be supported by a bearing plate inside the duct approximately 3 inches wide.
- The minimum size hanger wire for fibrous glass duct is 12 gage.
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Description
Fibrous glass duct construction standards based on SMACNA, 7th and 8th Editions. It covers topics such as temperature limitations, closure systems, sheet metal screws, and cross tabs for seams and joints.
