UL- 555/555S Test Ratings

Fire Rating : 3 hrs.

Leakage Rating : Class – I

Max Velocity : 2000 fpm

Operating Temperature : 250 °F (121 °C) for ½ hr

Max Operating Pressure: 4 in. w.g (1000 pa)

Standard Construction


16 gauge (1.4 mm – 1.7 mm) thick galvanized steel.


Parallel operated 3 ‘V’ type blade made of 16 gauge (1.4 mm – 1.7 mm) thick galvanized steel.

Blade Seals

Silicon rubber blade seals.

Jamb Seals

Stainless steel.

Jack Shaft

½” x ½” (12 mm) Galvanized steel square shaft.

Thermal Response Device (TRD)

165°F (74°C).


Honeywell, Belimo, Seimens (24V AC, 120V AC, 230V AC)


Minimum 0.9 mm, single section is field or factory installed.
Multiple section is factory installed.
Sleeve thickness as per NFPA table 3-4.6.3.

Optional Fittings

Retaining Angles

1½” x 1½” x 16 gauge (40 x 40 x 1.5 mm).

Limit Switches

For BMS open / close indication.


Externally mounted open, close visible Indicator.

Push Button

For manual reset of damper.

Transitions (R)

Neck adapter for round duct connections.

Junction Box

Model : MSFD-GB-31C1 -A/R UL 555/555S Damper meets the required standards of SMACNA, NFPA, IBC, BOCA, ICBO, UL.

Actuator location standard: Left side from rear view
(Jack shaft view)


Note :
FC : Fail Close in the event of Fire
FO : Fail Open in the event of Fire


* The temperature ratings are for Honeywell 20 Nm actuators with thermal enclosures.


Optional Construction (UL Certification N/A)

Frame : Stainless Steel 16 gauge (304/316L)

Blade : Stainless Steel 16 gauge (304/316L)


Type : Motorized Fire Smoke Damper
Fire Rating : 31 Series-3 hour
Leakage Rating : Class – I
Blade Type : 3V Single Skin; A : Parallel Operation
Construction :Galvanized Steel (GI)


MSFD B-31 Series is a high performance UL 555 / 555S Classified combination of fire and smoke damper with 3hr. fire rating , installed vertically or horizontally (with blades running horizontally) and is rated for airflow and leakage Class – I leakage in either direction


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