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Defective Dampers

Our firm received an assignment from the state to provide damper monitors on dampers contained in all of a developmental facility's cottages. These dampers were linked to the fire-alarm system. When an alarm came on or was tested, all dampers in the ductwork were supposed to close. When the alarm was lifted, all dampers were supposed to reopen. We were concerned that there was no way of knowing whether the dampers were functioning properly without inspection or individual testing. There were approximately 900 of these dampers on the site.

During the design phase, we asked the facility managers to provide an estimate of how many dampers might be inoperative. The estimate was 5 percent. In our specifications, we included a request for a unit price for a new motor and linkage tie-in. We included an estimate in our budget of $200 per unit.

The project began well, except that an overwhelming number of the damper motors were “defective.” After the monitors were installed, the state quickly decided to issue a new project to install new motors and linkage work. We designed the project, put it out for bid, and a contract was awarded. Still, we were concerned about the damper-motor failure and contacted the manufacturer, which quickly sent out its top service representative. We met him at the job site and went to a typical building. When we showed him an easily accessible installation, his first words were, “Where are the mounting brackets?”

The motor was bolted directly onto the duct run and linkage-pierced through to the damper inside of the duct. The technician explained that these motors were supposed to be installed with specific brackets that came with them. These brackets allowed the motor to “float,” in case of misalignment with the damper and linkage. He proved his point by loosening the mounting screws. The motor kicked in and did its job. The original installer had saved himself some time by not using the brackets. I had visions of some past inspector tugging on the motor, saying, “Good job — nice and tight!”

As we moved along, we found that more of these “bad” motors actually were working. However, it was decided to continue with the replacement project because the new units had stronger parts and gearing.

I shudder to think what might have happened if there had been a fire before we did the replacement work.
Albert R. Pressler, PE
J.A.R. Engineering Inc.
Flemington, N.J.

Send “war stories” to the attention of Scott Arnold, executive editor, at [email protected]. Authors are paid $50 per published war story.

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