HVAC FIRE DAMPERS - Fusible Links

[mtnelect]

Replaced an old package HVAC unit on the roof of an apartment building, for a unit on the first floor. Discovered that there was a Fire Damper with a Fusible Link that opened up in the return to the unit. The Fire Damper was located in the unit above behind a panel in the hallway. It was spring loaded and it closed. Could not find out why the return air wasn't working.

 

[kwired]

Had that happen once before. Cold winter day the furnace was running but was really hot and kept cycling on and off on high limit.

 

[gadfly56]

Replaced an old package HVAC unit on the roof of an apartment building, for a unit on the first floor. Discovered that there was a Fire Damper with a Fusible Link that opened up in the return to the unit. The Fire Damper was located in the unit above behind a panel in the hallway. It was spring loaded and it closed. Could not find out why the return air wasn't working.

Usually that has to be a temperature of at least 165F, and more likely 200F. Did someone mug the link?

 

[kwired]

Had that happen once before. Cold winter day the furnace was running but was really hot and kept cycling on and off on high limit.

IIRC what happened on this one was they had been testing the fire alarm, which closed the powered dampers whenever there was an alarm condition during the testing. The furnaces did have relays to shut them down when fire alarm is active, but for some reason one of the powered dampers failed to open again and eventually it got hot enough to melt fuse in the fusible link damper of that unit's ducting, which wasn't all that far from the furnace.

 

[mtnelect]

Usually that has to be a temperature of at least 165F, and more likely 200F. Did someone mug the link?

I think it was just a defective link ... no signs of melting !

Is there a requirement in the Fire Code for yearly inspections ?

 

[gadfly56]

I think it was just a defective link ... no signs of melting !

Is there a requirement in the Fire Code for yearly inspections ?

One year after the initial acceptance test, and every 4 years thereafter.

Fire and Smoke Damper ITM

What are the inspection, testing, and maintenance requirements for fire and smoke dampers?

www.nfpa.org

 

[brycenesbitt]

These fusible links can fail just based on vibration. It's a soft metal fusible link, and after a few years of shaking.... can develop cracks.
I'd say a really nice clear sign on the equipment could help alert techs to the condition!

 

[mtnelect]

These fusible links can fail just based on vibration. It's a soft metal fusible link, and after a few years of shaking.... can develop cracks.
I'd say a really nice clear sign on the equipment could help alert techs to the condition!

It really threw me ... I was going in circles.

 

[mtnelect]

One year after the initial acceptance test, and every 4 years thereafter.

Fire and Smoke Damper ITM

What are the inspection, testing, and maintenance requirements for fire and smoke dampers?

www.nfpa.org

Thank you for taking the time to post this information !