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Square aluminum backdraft damper galvanized steel frame 29.75 inches wide 4.5 inches deep

Dayton

Dayton 3HHL8 Backdraft Damper 29.75 In Square 4.5 In Deep

SKU CH-EHCA-9C8XZ

Aluminum backdraft damper for 30-inch square ducts, horizontal or vertical mount, 29.75-inch frame, 4.5-inch depth

  • Product typeNo Flange, Horizontal or Vertical Mount
  • No-flange design suits horizontal or vertical mounting
  • 75 in square frame fits 30 in rough opening
  • 5 in depth allows shallow duct installation
  • 20 ga galvanized steel frame resists corrosion
  • 2000 fpm max velocity handles high airflow

Square 30-inch duct fit

This backdraft damper fits a 30-inch square rough opening with overall dimensions of 29.75 inches by 29.75 inches and a depth of 4.5 inches. It is designed for vertical or horizontal mounting without a flange. The single-panel aluminum blade operates inside a galvanized steel frame rated for 20-gauge thickness.

2000 fpm velocity limit

The damper handles a maximum air velocity of 2000 fpm and a maximum pressure of 1 inch water column. It provides 6 square feet of free area for airflow. Exceeding these limits can cause blade flutter or incomplete closure.

No-flange frame mounting

The unit installs directly into the square duct opening using the 2-inch deep frame; no flange means fasteners must anchor into the surrounding ductwork. Installers sometimes forget to seal the perimeter, which lets air bypass the damper.

How it compares

Measured against everything we stock in General Hardware & Accessories, at today’s prices. Recalculated every night.

Price $85.99
Pricier than about 83% of the 2,607 comparable items (median $18.99).

Specifications

Product
Brand nameDAYTON
Product typeNo Flange, Horizontal or Vertical Mount

Questions about this item

What does the 2000 fpm maximum air velocity mean for airflow in a real installation?

The damper is rated for air speeds up to 2000 feet per minute, so it will open and close reliably in duct systems that operate within that velocity range without excessive pressure drop.

How does the 1 in wc maximum pressure rating limit the systems this damper can be used in?

It caps the static pressure differential the damper can withstand while remaining closed, making it suitable for low-pressure commercial or residential ventilation but not for high-pressure industrial fans.

What rough opening is required to mount the 29.75 in square damper?

A square rough opening of 30 inches by 30 inches is needed, and the frame depth of 2 inches must be accommodated within the duct or wall penetration.

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