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HVAC Smoke Detectors

jar546

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Look at the difference between the ICC IMC and the ICC based FBC here in Florida:
Thoughts?

FBC - 2020

606.2.1

To prevent the recirculation of dangerous quantities of smoke, a detector approved for air duct use shall be installed on the supply side of air-handling systems as required by NFPA 90A, Standard for the Installation of Air Conditioning and Ventilating Systems. Smoke detectors listed for use in air distribution systems shall be located downstream of the air filters and ahead of any branch connections in air supply systems having the capacity greater than 2000 cubic feet per minute.

Exception: Smoke detectors are not required in the supply air system where all portions of the building served by the air distribution system are protected by area smoke detectors connected to a fire alarm system in accordance with the Florida Fire Prevention Code. The area smoke detection system shall comply with Section 606.4.



ICC - 2018
606.2.1 Return Air Systems


Smoke detectors shall be installed in return air systems with a design capacity greater than 2,000 cfm (0.9 m3/s), in the return air duct or plenum upstream of any filters, exhaust air connections, outdoor air connections, or decontamination equipment and appliances.

Exception: Smoke detectors are not required in the return air system where all portions of the building served by the air distribution system are protected by area smoke detectors connected to a fire alarm system in accordance with the International Fire Code. The area smoke detection system shall comply with Section 606.4.
 
I never agreed with the NFPA 90A requirement to have them installed on the supply side of the unit. The smoke is captured and is not diluted in the return system if installed per IMC 606.2.1.
Smoke detectors installed on the supply side will be sampling diluted return air with the fresh air which means there may be a delay of shutting the unit down and preventing smoke from being distributed through out the building.
If you have electric strip heaters for heat the dust burning on the coils the first time the heat is turned on can trip the smoke detectors and if they are tied into the fire alarm system you will be rolling the fire trucks for no reason
 
I never agreed with the NFPA 90A requirement to have them installed on the supply side of the unit. The smoke is captured and is not diluted in the return system if installed per IMC 606.2.1.
Smoke detectors installed on the supply side will be sampling diluted return air with the fresh air which means there may be a delay of shutting the unit down and preventing smoke from being distributed through out the building.
If you have electric strip heaters for heat the dust burning on the coils the first time the heat is turned on can trip the smoke detectors and if they are tied into the fire alarm system you will be rolling the fire trucks for no reason
What if the blower motor catches on fire or starts smoking? Do you want to wait until it recirculates through the whole house/condo/area? Food for thought.
 
What if the blower motor catches on fire or starts smoking? Do you want to wait until it recirculates through the whole house/condo/area? Food for thought.
Both sides offer a level of protection, I would speculate a greater likelihood of smoke from a bldg fire over the rare occurrence of a blower smoking or and catching fire.

It would be valuable to read each of the original code proposals.

Would it make sense to offer code change of FBC and ICC to include one in the return and one in the supply?
 
If the blower motor catches fire then it probably will quit working.
The sole purpose of a duct smoke detector is to shut the HVAC unit down to keep it from sending smoke throughout the HVAC system to other portions of the building. There are many different systems out there that employ a number of different energy saving designs such as exhausting all return air to the exterior and bring 100% fresh air in on cool days. Neither code will determine the best place for duct smoke detectors in some of these designs.
 
I never agreed with the NFPA 90A requirement to have them installed on the supply side of the unit. The smoke is captured and is not diluted in the return system if installed per IMC 606.2.1.
Smoke detectors installed on the supply side will be sampling diluted return air with the fresh air which means there may be a delay of shutting the unit down and preventing smoke from being distributed through out the building.
If you have electric strip heaters for heat the dust burning on the coils the first time the heat is turned on can trip the smoke detectors and if they are tied into the fire alarm system you will be rolling the fire trucks for no reason
If you install in the Supply discharge, you can catch the fan motor that is overloaded and is starting to Cook! Is what I think, they were thinking
 
My experience as a Firefighter on the supply side, catches the smoking belt, or other air handler components burning up, had one last year with a cracked heat exchanger, gas fired save a bunch of CO ( not a CO detector a smoke detector) build up in the building. the dust build up is not problem in property maintained system.
 
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