Damper closed with a dead motor? Faulty actuator a different brand from the smoke damper?
Sometimes we hear from customers who find a smoke damper closed with a dead motor after spending significant time investigating why a zone has no airflow. Another scenario is a customer responding to a service call to replace “faulty actuators” to find the actuator on a smoke damper of a different brand. Typically, the question is, “What should I do first?”
These are common occurrences, and you definitely don’t want to refer the customer to another contractor, not to mention waste a trip. Read below for some helpful tips on where to start. If you are still unsure, snap a few photos with your phone and send them to our technical service team.
Where to start?
- Familiarize yourself, and your team, with the smoke damper codes and local codes. Take a look at UL555, UL555S and research the local practices. NFPA 80 and NFPA 105 are applicable to dampers and doors; get a copy and review them.
- Know your specific job’s control system sequence and smoke damper specifics (dimensions, torque, make, UL label, etc); estimate the scope of the repair/replace project.
- Discuss the technical situation and the specific application with the Authority Having Jurisdiction (AHJ), the local Fire Marshal, and the building inspectors. Assure them that the work will be done in accordance with local codes and “…in accordance with the damper manufacturer’s normal field servicing program.”
- Get the model number and any available information on the actuator being replaced. You may be able to replace it with a like-for-like model or you may need to replace it with new. Actuator replacement really starts with the damper, not the actuator. The same old motor can be applied in several ways, depending on the spring, thermal disc, etc. You will come across some very old models that cannot be directly replaced with a like actuator because they are no longer made or do not meet the new UL standards.
- If the actuator has an internal or external spring and there is a separate thermal sensor/high limit switch with reset, you should be able to replace the spring/actuator with a new model.
- If there are dual springs—one for the fusible link and one for the actuator—you should be able to remove the actuator and its spring while leaving the fusible link and its spring in place.
- Old dampers that use cables and pulleys generally must be replaced entirely; you can’t simply replace the actuator.