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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.)