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Trade Skills HVACR116
Sheet Metal
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Sheet Metal
• The most common types of duct material are:
– Aluminum– Fiberglass duct board– Spiral metal duct– Flexible duct
All of these types of materials have been used successfully
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Sheet Metal (cont.)
• The first type of metal going to be discussed is Galvanized-Steel Duct
• This particular metal is treated with a zinc coating to keep the steel underneath from corroding.
• Galvanized sheet metal comes in different thicknesses that are known as gauge.
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Galvanized-steel Duct
As the gauge number gets larger, the thickness of the sheet metal gets thinner.
• Ex. 30-ga galvanized sheet metal is 0.0157 inches thick, while 22-ga galvanized sheet metal is 0.0336 inches thick.
• Notice that the 22-ga metal is about twice as thick as the 30-ga
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Sheet Metal (cont.)
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Sheet Metal
• Sheet metal thickness is directky related to its weight.
• The Standard Gauge for Sheet Metal is 41.82 lb/ft2.
• This is a common factor, when multiplied by the thickness of the metal. You will get the weight of one square foot of the metal.
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• Ex. The thickness of 24-ga metal is 0.0239 in.
• Ex. The weight of 1 ft2 of this material is 1 lb
• lb=(0.0239 inches x 41.82 lb/ft2)
• Lb=.99 or 1
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Sheet Metal (cont.)
• Ex. Lb=(0.012 inches x 41.82 lb/ft2)
• Ex. Lb=
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Fiberglass Duct
• Fiberglass duct is also known as Duct Board.
• Fiberglass duct comes in 2 different styles
– Flat sheets
– Round prefabricated duct
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Fiberglass Duct (cont.)
• Fiberglass Duct Flat Sheets
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Fiberglass Duct (cont.)
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Fiberglass Duct (cont.)
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Fiberglass Duct (cont.)
• Round Prefabricated duct
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Spiral Metal Duct
• Spiral duct is used on large sytems.
• The duct is formed from flat metal and has seams all the way down the duct.
• It comes in 10’ lengths
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Spiral Metal Duct (cont.)
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Spiral Metal Duct (cont.)
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Flexible Duct
• Flexible duct also known as Flex, comes in sizes up to 24 inches in diameter.
• Some of flexible duct comes with or without insulation.
• Flexible duct comes in 25’ lengths.
• Code only allows us to run a maximum of 14’ per run out.
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Flexible Duct (cont.)
• Uninsulated
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Flexible Duct (cont.)
• Insulated
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Flexible Duct (cont.)
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