Fire & Life Safety: Pop Quiz for Powering Residential Fire Detection

Here's a pop quiz to determine your knowledge of what's right and wrong with power and residential smoke and fire protection systems


This article originally appeared in the August 2012 issue of SD&I magazine

Do you think you know all the ins and outs regarding the installation power requirements for residential smoke and fire alarm systems? Did you know that in one- and two-family homes, you should not use a dedicated AC circuit breaker to power interconnected smoke alarms? Are you still confident in your knowledge? Do you often confuse residential rules with the commercial requirements? Let’s try a few more questions to test your residential fire alarm system IQ.

Q. Does NFPA 70 require a “dedicated outlet” for powering the FACP of a combination home fire/burglar alarm systems when the outlet is located in an unfinished basement?

A. The following areas are required by the NEC to have GFCI protected outlets. As you can see, number five requires GFCI protected outlets in unfinished basements. However, the exception allows you to omit this protection providing the outlet only serves the fire/burg FACP.

“210.8 Ground-Fault Circuit-Interrupter Protection for Personnel.

FPN: See 215.9 for ground-fault circuit-interrupter protection for personnel on feeders.

(A) Dwelling Units. All 125-volt, single-phase, 15- and 20-ampere receptacles installed in the locations specified in (1) through (8) shall have ground-fault circuit-interrupter protection for personnel.  

(1) Bathrooms

(2) Garages, and also accessory buildings that have a floor located at or below grade level not intended as habitable rooms and limited to storage areas, work areas, and areas of similar use                      

           (3) Outdoors                      

Exception to (3): Receptacles that are not readily accessible and are supplied by a dedicated branch circuit for electric snow-melting or deicing equipment shall be permitted to be installed in accordance with 426.28.

(4) Crawl spaces — at or below grade level

(5) Unfinished basements — for purposes of this section, unfinished basements are defined as portions or areas of the basement not intended as habitable rooms and limited to storage areas, work areas, and the like.

Exception to (5): A receptacle supplying only a permanently installed fire alarm or burglar alarm system shall not be required to have ground-fault circuit-interrupter protection.”

This exception means the answer is “yes,” the outlet would have to be dedicated to the FACP. (This can be accomplished by the use of a single outlet receptacle, of a duplex receptacle, with one-half disabled by breaking the tabs feeding the second outlet.)

Q. Does NFPA 72 allow the audible trouble signal of a residential fire alarm system to be programmed as “silent” by the alarm company so that the rechargeable battery can be removed for service?

A. Look to Chapter 29 in the 2010 Edition of NFPA 72 to find five rules at, 29.6.2 “Household Fire Alarm Systems.” Rule number (3) contains the answer. Power for household fire alarm systems shall comply with the following requirements:

(1) Household fire alarm systems shall have two independent power sources consisting of a primary source that uses commercial light and power and a secondary source that consists of a rechargeable battery.

(2) The secondary source shall be capable of operating the system for at least 24 hours in the normal condition, followed by four minutes of alarm.

(3) The secondary power source shall be supervised and shall cause a distinctive audible and visible trouble signal upon removal or disconnection of a battery or a low battery condition.”

Since the audible trouble signal is required for the listing of the FACP, your technician cannot re-program this required function out of the system.

 Q. What is the maximum length of 16 AWG or 18 AWG conductor allowed to extend to the input leads of a power transformer powering a fire alarm system?

A. After the manufacturer’s published installation instructions, look to NEC article 760.127 “Wiring Methods on Supply Side of the PLFA Power Source,” which gives us the minimum rules for wiring transformers:

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