In reference to 725.3(C)
The following text is taken from Mike Holt's book, "Understanding Low-Voltage and Power Limited Systems," page 263.
(C) Ducts, Plenums, and Other Air-Handling Spaces. Where necessary for the direct action upon, or sensing of the contained air, Class 2 and Class 3 cables can be installed in ducts or plenums if they are installed in EMT, IMT, or RMC as required by 300.22(B).
Question:
Who, what, where, when, why, or how would an air-handling system ever need cable(s) or conduit to make it "necessary" or need to "sense" anything?
As far as I know, and I also heard Mike Holt say the same thing, these HVAC guys don't want anything in their duct work. I don't know, maybe I just don't get it.
The following text is taken from Mike Holt's book, "Understanding Low-Voltage and Power Limited Systems," page 263.
(C) Ducts, Plenums, and Other Air-Handling Spaces. Where necessary for the direct action upon, or sensing of the contained air, Class 2 and Class 3 cables can be installed in ducts or plenums if they are installed in EMT, IMT, or RMC as required by 300.22(B).
Question:
Who, what, where, when, why, or how would an air-handling system ever need cable(s) or conduit to make it "necessary" or need to "sense" anything?
As far as I know, and I also heard Mike Holt say the same thing, these HVAC guys don't want anything in their duct work. I don't know, maybe I just don't get it.