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BELIMO Americas, Fire & Smoke, Damper Actuators and Control Valves for HVAC Systems, V3AD, Pressure Independent Flow Control
Replacement Actuator Considerations and Most Common Questions

When considering replacement of existing, obsolete or defective fire and smoke actuators several considerations must be taken into account. The first consideration is whether replacing the actuator is truly the solution to the problem. In some cases a malfunctioning damper could be the result of a damaged blade or bent linkage; in that case, replace the damper with a properly UL listed assembly with the actuator factory installed from the damper manufacturer. If the actuator is the problem the primary considerations center on two decisive factors; code issues and technical issues.

First, what are the most important code issues for replacement?

UL has stated that replacement is governed by the Authority Having Jurisdiction and that UL assumes that replacement will be done in accordance with the damper manufacturer's instructions.¹

The primary intent of any code is to protect life and property and therefore dictates defective equipment must be replaced. What can vary is the interpretation of the details of a code requirement from one jurisdiction to another. This is typically the root cause of a majority of code compliance questions and leaves the final interpretive authority to the local inspector or Fire Marshal.

For clarity, Belimo recommends the following guidelines:

  1. Inspectors are looking for "Equal or Better" replacement actuators
  2. While replacement of a few actuators of the same type does not typically require a permit, some jurisdictions require a permit and inspections when a large number of replacements are needed or when changing model or function of the actuator.Use an actuator that is UL555S listed with the damper manufacturer.
  3. See the Belimo Fire and Smoke dashboard for a reference of UL listed Belimo actuated damper assemblies.
Second, what are the most important technical issues for replacement?

Specifying the proper replacement actuator depends upon the needs of the particular installation.


  1. Mounting of the actuator must not require any changes to the damper itself. For example, the old Prefco pulley and cable systems would require modifications to the damper. In this case, consult the damper manufacturer to see if the damper needs to be replaced.
  2. Equal or Better actuators should be used.
    • Current Draw: must be equal or lower than the original.
    • Voltage: must be the same. In the US: 90% are 120V, 10% are 24V.
    • Timing: IBC requires 75 seconds at elevated temperature. UBC requires 15 seconds at ambient. Know your local codes.
    • Temperature: FSLF and FSNF are rated at 350Replacement Actuator Considerations and Most Common Questions. FSAF is rated at 250°F.
    • Torque: must be equal or greater
  3. Torque requirements vary by damper manufacturer. For replacement in general:
    • Up to 4 sq.ft. = FSLF at 350°F.
    • Up to 12 sq.ft. = FSNF at 350°F.
    • Up to 16 sq.ft. = FSAF at 250°F.
    • Visually inspect the damper condition. Some older dampers can be corroded and gummed up; the torque requirement may be higher than originally passed UL.
  4. The damper and actuator Must Be Tested after replacement. Drive open, remove power to spring closed, and check for proper damper seal. Drive open again and check sensor using a heat gun to verify controls operation.

The administrative section of any code states that all mechanical and electrical systems, including life safety devices, must be kept in working order. Just as with gas valves, replacement permits and inspections are not typically required if nothing else is affected except the damper and actuator. However, a record of any action taken should be kept at the end user's facility.

The key is to understand your local codes and jurisdictions. Good communication with all related parties can smooth the way to less hassle when replacement is required.

Belimo Americas, 43 Old Ridgebury Road, Danbury, CT 06810
800-543-9038 USA | 866-805-7089 Canada | 203-791-8396 Latin America