Introducing the Sheet Metal Trade into your HVAC Program

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Introducing the Sheet Metal Trade into your HVAC
Program

• By Bob Feathers

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Introducing the Sheet Metal Trade into your HVAC
Program

• This program will help those instructors with
  limited sheet-metal field experience to introduce
  and teach this aspect of the trade to their
  students. It will also cover the need to add this
  portion of instruction to there existing HVAC
  curriculum.

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• With programs limited to space and budget, this
  is sometimes a difficult task to take on, or add
  to existing curriculum. We hope to show that this
  can be accomplished, with little change in lesson
  plans and minimum costs. Our contractors that
  hire our students are calling for improvements in
  this area.

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Course Content

• Sheet metal hand tools and proper use.
• Basic sheet metal fittings and accessories used
  in installation.
• Assemble trunk line and branch ducts.
• Importance of sealing and insulating ductwork.
• Basic system design.
• Sizing ductwork using a ductulator.
• Understanding the importance of proper airflow.

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Duck Types
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Duct Material

• Sheet Metal
• Snap lock seams
• Pittsburgh seams
• Cross break/Strength
• Use Drive cleats S-Strips

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Duct Material

• Sheet metal round pipe
• Snap lock applications
• Crimped one end, with airflow
• Fasten sections with screws
• Adjustable fittings
• Draw bands

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Duct Material

• Duct board
• Limited uses
• Seams and sections are Stapled/ Taped
• Seal when cut or modified

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Duct Material

• Flex-duct
• Seal all joints
• Mechanically fasten and tape to metal ducts
• Broad turns only
• Fasten every five feet
• Minimum lengths

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Duct Material

• PVC Pipe
• Plastic fittings
• Slab applications
• Glue, screw, and tape

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Duct Fittings

• Broadway 90s, 45s
• Turn right or left
• Inside turn called the throat
• Outside called the cheek

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Duct Fittings

• Short way 90s, 45s
• Used to turn up or down

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Duct Fittings

• Transitions
• Change duct sizes
• New furnace to existing duct retrofits
• Designed flat on side or centered

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Duct Fittings

• Offsets
• One piece used to turn right, left, down, or up
• Length important not to shrink size
• OWL method, offset times width divided by length

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Duct Fittings

• Plenums
• Supply or return applications
• Attaches to furnace/ air-handler
• Furnace flange/ hemmed on one end
• Avoid screwing into evaporator coils

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Duct Fittings

• Trunk-lines
• Extends plenum thru building structure
• Allows shorter branch ducts
• Properly sized for cfm

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Duct Fittings

• Tap collars
• Starts trunk line
• Straight take off
• Transitional
• Riser

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Duct Fittings

• Canvas connector
• Flexible connection
• Reduces vibration
• Isolates trunk line from plenum take-offs
• R/A, S/A Applications

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Duct Fittings

• End caps
• Used at the end of trunk lines
• Creates static pressure
• Never any take offs

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Duct Fittings

• Branch take-offs
• Collars
• Spin-ins
• Metal/ Duct board applications

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Duct Fittings

• Dampers
• Adjust airflow
• Installed beginning of branch duct
• Used in zone applications

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Duct Fittings

• Branch ducts
• Connected to register boots
• Minimum lengths
• Minimum turns
• Sheet metal/ Flex applications

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Duct Fittings

• Stack Ducts
• Vertical extension of branch ducts
• Fits in wall stud space
• Sizes are 3 ¼ x 10,12,14

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Duct Fittings

• Boots / Stack heads
• Terminates branch ducts
• Straight, end, 90 applications
• Fastened to structure
• Should be sealed

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Duct Fittings

• Registers
• Supply air termination
• Adjustable air flow and throw
• Floor, ceiling, and side wall applications

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Duct Fittings

• Grilles
• Return air inlets
• Non-adjustable
• Floor, ceiling, and side wall applications
• Filter grilles recommended

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Installation Considerations

• Sized properly to load
• Securely fastened and supported
• Use a minimum amount of screws
• Fewest possible turns and off-sets
• No take offs on end caps or fittings
• Seal all joints and seams
• Insulate in unconditioned spaces

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System Design Considerations

• Crawl space, attic, slab, and basement
  applications
• Load requirements
• Air flow, cfm, noise, drafts
• Duct design application
• Structure considerations

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Duct designs

• Plenum system
• Extended plenum
• Reducing extended plenum
• Perimeter loop

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