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Today's Motorized Life Safety Damper Reliability

by Kent Maune, Sr. Product Manager and Western Regional Sales Manager at United Enertech

Motorized fire, smoke, and combination fire/smoke dampers and their testing requirements have come a long way since their release in the 1970’s.

Initially, these were standard commercial control dampers with blade locks to hold them closed. They were UL tested to the third edition of UL 555, Standards for Fire Dampers, and the first edition of UL 555S, Standard for Smoke Dampers.

The testing consisted of fire, 250 cycle, and heat-degradation tests. The actuator was whatever type of motor could operate the damper. UL did not have a test procedure for actuators, so damper manufacturers had to list on products the actuator tested. The dampers did their job because the actuators did not have to operate under fire conditions. The dampers utilized a fusible link connected to the damper blades and a shaft connected to the actuator. During a fire event, the actuator would disconnect form the shaft, a spring would close the damper, and a locking device would lock the blade closed. Because of the fusible link, full access to the damper via an access door was required for visual inspection and testing.

In the ensuing years, major changes were made to improve the efficiency of motorized fire, smoke and combination fire/smoke dampers. Today they have their own UL 555S (fourth edition) test requirements, and there is a new test standard for actuators and dynamic assembly operation.

Dampers no longer are glorified control dampers; they are specially designed to operate during exposure to high temperatures and velocities control dampers are not required to endure. Also, they no longer utilize fusible links and blade locks to close under fire conditions. They now are designed with a jackshaft with a solid connection between it and the blades, so, when a damper is closed, the blades are locked into position.

Examples of Combination Fire and Smoke Dampers

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The F/S-3V-I is a class I leakage combination fire smoke damper. It is UL classified and tested per UL 555 & 555S.


The F/S-RD-I is a true round, class I combination fire smoke damper.


Actuators have evolved from an oil-filled foot-mounted motors with complicated linkages subject to breaking to anti-slip, direct-coupled devices specially designed and UL-tested, going through rigorous cycle and holding tests.

The Belimo FS-AFB-24SR(S) is a modulating 24V Fire/Smoke Actuator (option end-switch).


UL555 and UL555S, meanwhile, have been updated to meet today’s building HVAC and smoke-evacuation systems. The standards require damper and actuator assembly to be cycle-tested for a minimum of 20,000 cycles and subjected to a heated-air-dynamic-closure-and-operation test with a minimum temperature of 250° F (121°C), a minimum air velocity of 2,400 fpm (10.2 m/s), and a system pressure of 4 in. wg. (1 kPa).

UL has a follow-up procedure that includes spontaneous inspections at manufacturers’ facilities to ensure everything is being built as tested, without modifications.

UL requires installation instructions accompany each shipment of dampers, so contractor will have the most up to date instructions.

With all of the standards to which UL motorized dampers must adhere before being shipped to a job site and requirements for proper installation, after the first visual inspection and visual commissioning of a building, there should be no reason that motorized dampers cannot be remote tested with today’s technology.

With dampers operating with fusible links, visual inspection is the proper procedure for testing as there is no other way to determine if an issue exists. With motorized dampers, there are multiple ways remote testing can be accomplished:

Control Panel

A control panel can be hard-wired directly to a damper with a monetary push button.

Computerized Fire Alarm Panel

Requirements for damper testing vary from country to country. For example, in Europe, some countries require testing as often as every 48 hours, performed by a computerized fire-alarm panel that notifies users if something is wrong.

Remote Control

Technology similar to that allowing us to control our homes using a hand-held device, can be used to test UL-listed motorized dampers.

Electric Remote Control Systems



The United Enertech "Electric Remote Control Systems" was developed as an alternative to manual cable remote systems. It provides personal convenience and a positive means of individual room or zone air flow. In addition, outside air intake or exhaust can be controlled. It allows 0-100% airflow control. The system is composed of an electric wall controller and matching actuator. A single controller will operate up to 10 actuators at up to 3000ft away. All United Enertech dampers and adjustable louvers are available with this option.

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Because of the accuracy and reliability of modern dampers and testing equipment, intrusion into ceiling cavities to test dampers no longer is necessary, saving on ever-rising labor costs. Remote-testing could reduce the cost of testing up to $500 a damper. With this type of savings, visual inspection of motorized dampers no longer would be necessary.

About Kent Maune

Kent Maune

Kent has been in the HVAC (Damper and Louver) industry for more than 37 years. He's held positions in Engineering, R&D, Operations, Sales, and Product Management. For the last ten plus years, he has been a Life Safety Damper Product Manager and a Commercial Damper Product Manager. Kent joined United Enertech in 2022, and his responsibilities include development and marketing of Life Safety Product lines, including testing, manufacturing and field application of Underwriters Lab classified and listed products.