Questions and Answers about Replacement of Fire &Smoke Actuators

What is the difference between a control and a fire & smoke actuator?

Fire and Smoke actuators are essentially the same as regular control actuators. They tolerate 250°F or 350°F for a half hour and must operate in less thFire and Smoke Damper Actuatorsan 75 seconds to open or to close per UL555S or in 15 seconds for replacement in regions where UBC times are required. Las Vegas requires 60 seconds or less, so the 15 second actuators are used there. The one exception is the FSAF24-BAL which springs in 20 sec and drives open in 60 seconds worst case since the potentiometer’s lowest setting is 20% (80% of 75 sec = 60 sec).

Can linkages be used with the FS series actuators?

The data sheets for each actuator indicate that:

    • FSLF is direct coupled only.
    • FSNF and FSAF can use the full range of linkages and housings.

What are the most important code issues for replacement?

All codes require life safety systems to be in working order and defects to be corrected. Interpretations on the details vary within different jurisdictions. UL has specifically stated that they do not regulate replacements and that the local inspectors are the final authority. The codes themselves do not detail replacement rules, so the Authority Having Jurisdiction (AHJ, usually the Fire Marshal or Building Official) interpret the codes and inspectors vary in interpretations. NFPA 80 regulates fire dampers. NFPA 105 regulates smoke dampers. They both require repairs be initiated as soon as possible and that a record of corrections be kept on premises.

While they do not regulate the replacement of old actuators, UL does state that they expect repairs be done in accordance with the manufacturer’s field servicing policy. Belimo provides replacement installation instructions for this purpose.

Always use an actuator that is UL555 and UL555S listed with the damper manufacturer. One or more of the Belimo actuators is UL555(S) listed with each.

In general, inspectors want an “equal or better actuator”. Some jurisdictions require a permit and inspection when a large number of replacements are needed or when changing model or function of actuator. This varies. In most jurisdictions, actuator replacement is considered an “ordinary repair”.

If any fire alarm wiring is touched or if any structural modifications made, a permit and inspection may be required. Retest of the alarm functions should be expected.

Retesting of the damper is expected and sometimes witnessed. The Belimo instructions include a testing checklist.

Belimo has New York City MEA approval and tags are shipped with actuators going into that area.

Belimo has California State Fire Marshal Listing on the FSLF and FSNF and the FSAF has been submitted.

What are the most important technical issues to look at for replacement?

  • Equal or better actuators should be used.

TTT-VAT is a mnemonic device that can be used:

  • Time: Actuator should operate as fast or faster than the old motor. The exception is that the UBC 15 second time is no longer in effect. The UL 75 second time is now code. Consult with AHJ if going to slower time.
  • Temperature: The FSLF and FSNF are rated at 350°F. The FSAF is for 250°F. Codes in the US are 250°F. 350°F is used in some engineered smoke control systems, but is not a code issue.
  • Torque: Replacement must be equal or greater. Requirement varies by damper manufacturer depending on their UL555(S) testing. For replacement in general:
    • 4 sq. ft. or less = FSLF at 350°F.
    • Up to 12 sq. ft. per FSNF at 350°F.
    • Up to 12 sq. ft per FSAF at 250°F.

While the actuators may be capable of more damper area, without a test to prove it, the UL tested torque should be used. Both the FSNF and FSAF have been tested for large multi-section assemblies also. Details are available.

Actuators listed above can operate a greater area than stated, however some old dampers are corroded and dirt has gummed up parts. Some shifting of ducts may have occurred and the torque requirement may be higher than originally passed by UL. The actuator output is higher and the damper requirement lower at ambient than at elevated temperature. The operation at elevated temperatures is the important factor. Spare torque should be provided.

  • Voltage: Must be the same. In the US 90% are 120V, 10% are 24V. Only the FSAF can take DC power.
  • Amperage: Must be equal or lower than the original. Belimo is lowest and can replace all competitors of the same torque without fear of overloading a breaker.
  • Test: Damper should be operated 3 times open to close to ensure proper operation. The damper and actuator must be tested after replacement. Just like a gas valve replacement, the contractor takes responsibility.

In most cases, drive open, open the sensor or remove power to ensure that the actuator springs the damper closed. Then drive open again, check sensor (use a heat gun) and controls operation as described in Conformance Testing.

Learn more.

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