duct smoke detec. location

[Toros]

Hi,
anybody knows where my eletrition should install a smoke duct detector
in supply or return HVAC plenum ???
I know that this not Mechanical forum!!

thank you

 

[jumper]

Here is a link with basic requirements.

http://www.ecmag.com/section/codes-standards/duct-detectors

 

[david luchini]

Hi,
anybody knows where my eletrition should install a smoke duct detector
in supply or return HVAC plenum ???
I know that this not Mechanical forum!!

thank you

In California, the supply ductwork.

 

[gadfly56]

In California, the supply ductwork.

There is a kind of Catch-22 here. In general, if your jurisdiction follows NFPA 72 and the International Mechanical Code, you will be installing detectors in both the supply and return.

NFPA 72 references NFPA 90 and requires them in the supply duct (NFPA 72-2013, 17.7.5.3.1).

The IMC requires them in the return duct (IMC-2015, 606.2.1).

If the system is under 2,000 CFM they are usually not required, unless multiple systems serve the same area and have an aggregate flow of 2,000 CFM or greater.

 

[david luchini]

There is a kind of Catch-22 here. In general, if your jurisdiction follows NFPA 72 and the International Mechanical Code, you will be installing detectors in both the supply and return.

NFPA 72 references NFPA 90 and requires them in the supply duct (NFPA 72-2013, 17.7.5.3.1).

The IMC requires them in the return duct (IMC-2015, 606.2.1).

If the system is under 2,000 CFM they are usually not required, unless multiple systems serve the same area and have an aggregate flow of 2,000 CFM or greater.

No Catch-22. The California Mechanical Code requires duct smoke detectors to be installed in the supply ductwork.

 

[steve66]

No Catch-22. The California Mechanical Code requires duct smoke detectors to be installed in the supply ductwork.

California actually passed a helpful requirement that clarifies the conflicting requirements of two other codes?

Must of been an off day!!!

 

[gadfly56]

No Catch-22. The California Mechanical Code requires duct smoke detectors to be installed in the supply ductwork.

So, California decides to go with a reduced level of fire protection.:? Very atypical of the People's Republic. And you may notice I started my previous post with the word "if".

 

[david luchini]

So, California decides to go with a reduced level of fire protection.:? Very atypical of the People's Republic. And you may notice I started my previous post with the word "if".

Shutting down air handlers greater than 2000CFM upon the detection of smoke in the ductwork isn't a reduced level of fire protection.

And I noticed you started your previous post with the word "There."

 

[gadfly56]

Shutting down air handlers greater than 2000CFM upon the detection of smoke in the ductwork isn't a reduced level of fire protection.

And I noticed you started your previous post with the word "There."

True enough. And I failed to note that the OP is in California. My bad.

However, return duct detection helps prevent filling the duct system with smoke, especially where you have multiple floor returns. Also, you can push supply air with noticeable smoke odor through the building before the concentration is high enough to trip the detector.

 

[steve66]

True enough. And I failed to note that the OP is in California. My bad.

However, return duct detection helps prevent filling the duct system with smoke, especially where you have multiple floor returns. Also, you can push supply air with noticeable smoke odor through the building before the concentration is high enough to trip the detector.

For non- California locations: I've never heard of anyone actually installing detectors on both the supply and return (unless its over the next CFM limit where both are required.)

Usually the AHJ favors one location or another, and one detector is fine. The trick is knowing which location your local AHJ prefers to avoid rework.

 

[david luchini]

For non- California locations: I've never heard of anyone actually installing detectors on both the supply and return (unless its over the next CFM limit where both are required.)

Usually the AHJ favors one location or another, and one detector is fine. The trick is knowing which location your local AHJ prefers to avoid rework.

You should visit New Hampshire. They require detectors in both the supply and return ductwork for systems over 2000 CFM.