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Square galvanised-steel frame with aluminium damper panel, 21 by 21 inches, roof-mount backdraft damper

Dayton

Dayton 4HX66 Backdraft Damper, Roof Mount, 21 in

SKU CH-9FAC-TY5CN

Aluminium backdraft damper with galvanised-steel frame fits 18-inch roof-mounted exhaust fans

  • TypeRoof Mount, Exhaust
  • Fits 18 in fan with 19 1/2 in rough opening
  • 2000 fpm max velocity handles strong exhaust flow
  • 9 sq ft free area reduces airflow restriction
  • Galvanised steel frame with 20 ga thickness resists corrosion
  • 21 in square aluminium damper mounts directly on roof

Dayton 4HX66 Backdraft Damper

The Dayton 4HX66 is a roof-mount backdraft damper built for exhaust applications. Its frame uses galvanised steel and the blade is aluminium. The unit measures 21 in overall height and width with a 4.5 in depth. A single panel provides 1.9 sq ft of free area for airflow.

Square rough opening and fan fit

The damper fits a square rough opening of 19 1/2 in by 18 1/2 in and matches an 18 in fan diameter. The 20 ga frame thickness and 2 in frame depth allow direct mounting to the roof curb. Gravity operation means no actuator or wiring is required, freeing electrical capacity for other equipment.

Suits gravity exhaust on square ducts

This model suits installers needing a simple gravity damper for square ductwork up to 2000 fpm. It is not for motorised control, round duct connections, or systems requiring insulated blades. Buyers needing powered actuation or a different rough-opening size should look at other configurations.

Highlights

  • Fits 18 in fan with 19 1/2 in rough opening
  • 2000 fpm max velocity handles strong exhaust flow
  • 9 sq ft free area reduces airflow restriction
  • Galvanised steel frame with 20 ga thickness resists corrosion
  • 21 in square aluminium damper mounts directly on roof

Specifications

BrandDAYTON
TypeRoof Mount, Exhaust

Questions about this item

How long will the 20 ga galvanized steel frame last under continuous 2000 fpm airflow?

The 20 ga galvanized steel frame resists corrosion and deformation at the rated 2000 fpm maximum air velocity, maintaining structural integrity during continuous exhaust operation.

How much noise and heat does the single aluminum panel generate when running all day?

The single aluminum backdraft panel operates passively with no motor, so it adds no mechanical noise or heat; airflow sound depends on the connected fan and duct design.

What roof opening must already exist for this 21 in square damper to fit?

A square rough opening of 18 1/2 in by 18 1/2 in is required to mount the 21 in overall width damper with its 2 in frame depth.

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