3/4 conduit for fire alarm circuits

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user-716992's picture
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Joined: 2015-08-31

From the beginning of my 15 year+ career in fire alarm installations and repair, I was told that use of 3/4 inch conduit for fire alarm circuits was dictated by electrical code. I am now being pressed to locate such code(s),and can not locate any code(s) stating this. Can anyone shed some light on this?

span's picture
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Joined: 2013-11-26

NEC 2011
Sec. 760.49 NPLFA circuit conductors
(A) size and use. Only copper conductors shall be permitted to be use for fire alarm systems. size 18 and 16 AWG conductors shall be permitted to be use, provide they supp;y loads that do not exceed the ampacities given in Table 402.5 and are INSTALLED IN A RACEWAY, AN APPROVED ENCLOSURE, or a listed cable.

Maybe this is the conduit they're talking about.

sparky377's picture
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Joined: 2013-10-07

Have you reviewed NEC Articles 725 [Remote-Control & Signaling Circuits] and 760 [Fire Alarm Systems]? Both of these Articles have minimum size requirements for conductors, but not raceways.

Could there be a local amendment to the NEC when it was adopted in your jurisdiction?

In addition, you will need to reference NFPA 72 Fire Alarm Code. I cannot speak to the requirements in 72 as I do not have a copy at hand. However, I do not recall it having a minimum size conduit requirement. If there were, I would expect it to show up in NFPA 70.

As a side note, when I started in this field after college I was told to never use smaller than 3/4 inch conduits. It was not a Code requirement; just a design preference stated as if it was required by Code. I suspect you are experiencing the same situation.

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