How to Install a Hardwired Smoke Alarm – Part 2

The hardwired smoke alarms were never connected to an AC power circuit. A new metal junction box is installed and the existing smoke alarms are wired to a continuous non-switched circuit for power. The new smoke alarms are then wired and installed.

This project is continued from How to Install a Hardwired Smoke Alarm – Part 1.

How to Install a Hardwired Smoke Alarm

The smoke alarms in my house are 10 years old and will be replaced with new Kidde/Firex® Dual Sensor (Ionization and Photoelectric) 120VAC powered hardwired alarms with battery backup. I chose the Consumer Reports #1 rated Kidde PI2010 alarm that sells for about $30. See the PI2010 User Manual for detailed installation and operation instructions:

Install a Kidde/FIREX Smoke Alarm Model # PI2010

Install a Kidde/FIREX Smoke Alarm Model # PI2010

The alarm includes the 9 volt battery – a nice touch to get started.

Hardwired Smoke Alarm Wiring Diagram

In How to Install a Hardwired Smoke Alarm – Part 1 I described how the smoke alarm in the finished basement was disabled and improperly concealed in a ceiling crawl space in violation of the Building Codes. The scope of work for this project is to:

  1. Remove the old smoke detector and ceiling electrical box.
  2. Wire and install a new smoke detectors in both the finished and unfinished sections of the basement.

120VAC power for the smoke alarms will provided by a new branch circuit from an existing junction box on a continuous (i.e. non-switched) circuit. The new work is indicated by the green box in this wiring diagram:

Hardwired Smoke Detector Wiring Diagram with NM-B 14/3 cable

Hardwired Smoke Detector Wiring Diagram with NM-B 14/3 cable

The smoke detectors are hardwired as follows:

  • 120VAC power is provided by the hot (black) and neutral (white) wires.
  • Interconnect alarm signaling is carried by the red wire. If one alarm is triggered, it will signal the other alarms to sound.
  • The neutral (bare copper) wire is not used by the smoke alarms and no connection is required. However, I connect the ground wires between the different cable runs as a matter of personal preference. A continuous ground wire is your friend in safety.

If you’re not comfortable and experienced working with 120VAC wiring, I strongly recommend hiring a licensed electrician.

Smoke Alarm Placement

The National Fire Protection Association (NFPA) and the Kidde PI2010 Smoke Alarm Users Manual provide detailed guidance on where to install smoke alarms. In brief, smoke alarms should be installed:

  • On every level of the home, including the basement.
  • On the ceiling if possible, at least 4 inches away from the wall.
  • Outside of every bedroom on older homes to comply with the old rules.
  • New homes must have a smoke alarm in every bedroom and all smoke alarms must be interconnected.

Do not install smoke alarms:

  • Near windows, doors and heating/cooling vents because drafts can interfere with the detector.
  • In the attic.
  • In crawlspaces.

Smoke Alarm Installation Tools

The following tools were needed to wire and install the smoke alarms, moving clockwise from the top these are:

  • Drywall jab saw
  • Cordless drill/driver
  • Needle nose pliers with cutter
  • Wire stripper / cutter
  • Utility knife
  • Non-contact voltage detector
Hardwired Smoke Alarm Installation Tools

Hardwired Smoke Alarm Installation Tools

Smoke Alarm Wiring: NM-B 14/3 versus NM-B 14/2 Cable

Before I begin wiring the new smoke alarm, I’ll take a moment to explain the two types of electrical cable that I’ll be using.

NM-B 14/3 wire means Non-Metallic 14 gauge, 3 conductor plus ground. The ‘B‘ designates the application – for exposed or concealed work in normally dry locations such as inside the home. The conductors are:

  • Hot (black) or line side.
  • Neutral (white).
  • Red – used here for alarm interconnect signaling, so if one alarm goes off, they all sound.

plus the bare copper ground wire. The smoke detectors are ungrounded and the ground wire is not used.

NM-B 14/2 is a 14 gauge, 2 conductor plus ground wire. Two conductors are:

  • Hot (black) or line side.
  • Neutral (white).

I used NM-B 14/2 wire to run a new AC branch feeder circuit to power the alarms (see the junction box at the far right of the above wiring diagram).

Smoke Detector Wiring: NM-B 14-3 versus NM-B 14/2 Cable

Smoke Detector Wiring: NM-B 14-3 versus NM-B 14/2 Cable

In this project, I’ll use the terms “wire” and “cable” somewhat interchangeably. Strictly speaking, “cable” refers to the entire NM-B wire bundle with the outer insulation jack where “wire” refers to an individual conductor within the cable.

Unfinished Basement Smoke Alarm Installation

I began by removing the old smoke alarm and ceiling box from the crawlspace above the finished basement; recall that I determined after careful analysis there is no AC power on the alarm circuits. The new smoke alarm will be located nearby in the unfinished area of the basement where the gas furnace, gas water heater and my workshop are located. The new position is only about 5 feet away but in a much more accessible location. I’ll reuse the existing NM-B 14/3 cable that interconnects to the the other smoke alarms in the home:

Basement Smoke Alarm Installation: Relocate the Alarm Wiring

Basement Smoke Alarm Installation: Relocate the Alarm Wiring

Smoke Alarm Ceiling Junction Box Wiring

An octagon ceiling box is installed on the floor joist to wire in the new smoke alarm. The existing NM 14/3 alarm wire from the upper floors is brought in on the left and new cables are brought in on the right side: NM-B 14/2 for power and NM-B 14/3 for the second smoke alarm to be installed in the finished basement area. Remember the red wire in the NM-B 14/3 cable is needed for the smoke alarm signaling interconnection.

Note: The smoke alarm trim plate will not fit a 4″ square junction box, you must use an octagonal or rectangular ceiling box. I chose the deep octagon box because it can handle four cables without exceeding the box fill capacity per the National Electrical Code (NEC):

Smoke Alarm Octogonal Ceiling Box Wiring

Smoke Alarm Octogonal Ceiling Box Wiring

The above photo corresponds to these cables in the wiring diagram:

Smoke Detector Octogonal Wiring Diagram

Smoke Detector Octogonal Wiring Diagram

5/8 inch of insulation is stripped from the wires, then the wires are matched by color, right-twisted (clockwise) together and secured by a wire nut to the Kidde PI2010 AC Quick Connect Harness. A #10-32 green ground screw and ground wire pigtail is fastened to the junction box, then twisted and nutted with the other ground wires. Metal junction boxes must be grounded per NEC 250.148 (C).

Firex PI2010 Smoke Alarm: Junction Box Electrical Wiring

Firex PI2010 Smoke Alarm: Junction Box Electrical Wiring

The wires are tucked into the ceiling box with the AC Quick Connect hanging down as shown:

Octogonal Ceiling Box Smoke Alarm Wiring

Octogonal Ceiling Box Smoke Alarm Wiring

The AC Quick Connect pigtail is inserted through the trim plate, the trim plate fastened to the octagonal ceiling box with two screws (included with the ceiling box) and the AC Quick Connect plugged into the smoke alarm.

Kidde PI2010 Smoke Alarm Trim Plate and AC Quick Connect Installation

Kidde PI2010 Smoke Alarm Trim Plate and AC Quick Connect Installation

The smoke alarm is mounted to the trim plate by twisting on until it ratchets into place.

120VAC Branch Circuit Smoke Alarm Wiring

A new run of NM-B 14/2 cable is installed between the octagonal ceiling box and a convenient junction box on the wall about 10 feet away. The junction box is on a circuit that is connected at the main electrical panel. It’s extremely important the smoke alarms are on a continuous non-switched circuit and not to a light switch.

The new circuit for the non-switched (or full time) AC power is highlighted in the wiring diagram:

Smoke Detector AC Branch Circuit Wiring Diagram

Smoke Detector AC Branch Circuit Wiring Diagram

Electrical Safety: Be certain to shutoff the electricity at circuit breaker or fuse box. Confirm the circuit is dead with the voltage detector to prevent shock, burns, fire and/or death.

The new NM-B 14/2 cable run for the smoke alarm power feed is routed to an existing junction box and wired. Remember to secure your new cable with insulated cable staples within 1 foot of the junction box and every 4 or 5 feet along the floor joists or 2×4 wall studs:

Smoke Alarm AC Power Feed: Branch Circuit Wiring

Smoke Alarm AC Power Feed: Branch Circuit Wiring

If you don’t have a convenient junction box to splice into, you can splice into an existing circuit as explained in this project.

Jumping ahead for perspective, I’ve installed the 2nd smoke detector in the next photo. The green AC power indicator glows when the alarm is on 120VAC power. For now, the circuit breaker and AC power must remain shutoff.

Kidde PI2010 Smoke Alarm: Green LED AC Power Indicator

Kidde PI2010 Smoke Alarm: Green LED AC Power Indicator

The second smoke detector is installed in a finished basement room in How to Install a Hardwired Smoke Alarm – Part 3.

Thanks for reading,

Bob Jackson

Copyright © 2014 HandymanHowTo.com   Reproduction strictly prohibited.

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35 Responses to How to Install a Hardwired Smoke Alarm – Part 2

  1. Siera January 17, 2013 at 7:30 pm #

    The other morning my smoke detectors started going off and i could not get them to shut off. I cut the black wire in one of the alarms and now my bathroom lighting (which is on the same circuit breaker) is not working. what do i need to do to reconnect the wire and get my bathroom lights back working?

    • BobJackson January 18, 2013 at 8:44 am #

      Uh oh! You’ve cut a 120 volt AC wire on the circuit that powers the smoke detector and bathroom lights. You’re lucky you weren’t shocked or worse! What you’ve got now is an exposed line-side live wire that is a shock and fire hazard. I strongly recommend that you call licensed electrician to repair the wiring. It shouldn’t be an expensive as I believe the electrician can repair the cut wires with a new pigtail connection in the ceiling box. Also ask the electrician to troubleshoot the original smoke detector problem.

  2. Brian Krenicky February 19, 2013 at 12:31 pm #

    Hey Bob

    I am remodeling a home that tennets have destroyed in Bangor, PA. It was built in the late 1800’s and I was contracted to restore it. Since it has wood lath and horse hair plaster which has been destroyed in so many rooms, I had to gut the entire home and start over. It even had all the piping for gas lighting for every room which was not operable.

    Someone has remodeled at some point but as usual, i found lots of code violations. I am surprised that thier was no fires. In any event, I am installing fire/smoke alarms and i was researching code requirements and came across your page. I understood already that because i had to gut the house it falls under the new constructions codes and not existiing structure codes.

    I first want to say your pages are awesome and very through. I love the schematics, pictures, and not to mentions your explanations are very detailed as well. Second, i just want to say thankyou for taking the time and putting together these pages. I am not sure if you got many comments on them but when i see good work i like to present credit where it is due.

    You have answered all of my questions and I want to say thank you. I guess that is all for now. Talk with you later.

    Brian

    • BobJackson February 19, 2013 at 6:06 pm #

      Brian,
      Thanks for sharing your story and the compliments. That’s an unusual restoration job! Reminds me of an older house my wife once wanted to buy. The house was in a great location on the bay, but I thought it was a money pit and would be washed away with the first hurricane.
      Good luck!
      Bob

  3. chris May 19, 2013 at 2:56 pm #

    I am going through a similar experience. My 4 hardwired 2nd floor detectors have no power. I have one in the hall outside of three bedrooms. The hallway unit has three lines of 14/3 in the box. two bedrooms have two lines of 14/3 and one bedroom has one line of 14/3. There is no voltage what so ever. Did someone forget to install a hot line? Where would be the best place to get power to the Hallway unit.

    • BobJackson May 19, 2013 at 4:52 pm #

      What I would so is:
      * Check the circuit breakers to see if any are tripped. If so, reset it and check for power at the smoke alarms.
      * Check for tripped GFCI wall outlets, the type with a Set/Reset button on the face. Reset the GFCI outlet and check for alarm power. Consider re-wiring the smoke alarm so it’s not on the GFCI outlet.
      * Turn on all light switches and check the smoke alarms for power. Someone may have incorrectly wired it to switch-controlled circuit.

      If still no power:
      * Trace the NM-B 14/3 cables in the attic or crawlspace. Look for damage to the cables – breaks, kinks, repairs, rodent bite marks, etc. – or an unconnected cable. Make necessary repairs depending on what you find, if anything.

      If you still can’t trace all the cables and find the problem, I would be very cautious about connecting the smoke alarm circuit to a convenient junction box for power because a hidden break or unconnected NM-B 14/3 cable could short and/or start a fire when energized. At this point it’s best to call a licensed electrician and ask him to trace the wires.

      Let me know what you find.

      Thanks,
      Bob

  4. chris May 19, 2013 at 5:34 pm #

    Bob,
    thanks for the speedy reply. All circuits are in working order. All light switches and receptacles are working. The GFCI’s are not tripped either. I wish I could follow the wires in the attic but I have plywood covering the joists. I guess I have to call an electrician.
    I will let you know

    • BobJackson May 19, 2013 at 7:42 pm #

      > I wish I could follow the wires in the attic but I have plywood covering the joists.
      It shouldn’t be difficult to pull up only those sections of plywood necessary to follow the wires with a hammer and flat nail bar. It’ll make the electrician’s job easier (i.e. less expensive) too. Use wood screws to reattach the plywood so future access will be easy.

      Good luck!

  5. chris May 21, 2013 at 1:09 pm #

    Bob,
    well here is the deal. I traced all the wires coming out of the hallway box. I had to raise a few pieces of attic flooring to do so but it helped. As I said earlier all the smoke detectors had 14/3 in them. Hallway (box #1) had 3 lines (ABC), 2 bedrooms (boxes # 2&3) had 2 lines and one bedroom (box #4) had 1 line. So lines (ABC) out of the hallway, I discovered that line( A) went to bedroom( box #3) which had a line out to (Box #4) bedroom. So back to the hallway, line (B) went to bedroom (Box #2). So where did line (C) go…???? It went to the (Box #2) as well.
    Basically the hallway box had two lines of 14/3 going to one bedroom, one line going to another bedroom and then that bedroom tied over to the last bedroom with a single line. I disconnected and pulled out one of the two lines to the #2 box. I then ran some 14/2 from a hot source and now I have power to all the smoke detectors.

    • BobJackson May 21, 2013 at 8:42 pm #

      I’m happy you found the wiring problem by pulling up the plywood attic floor and tracing the smoke alarm wiring.

      To summarize, what you found was a closed system with no power feed:

      [Hallway Box #1]—NM-B 14/3—[Bedroom Box #3]—NM-B 14/3—[Bedroom Box #4]
      ||
      || Two runs of NM-B 14/3 cable to Box #2
      ||
      [Bedroom Box #2]

      And fixed the problem by removing the redundant cable strand and wiring a new circuit for power:

      [Hallway Box #1]—NM-B 14/3—[Bedroom Box #3]—NM-B 14/3—[Bedroom Box #4]
      |
      | Remove one redundant run of NM-B 14/3 cable to Box #2
      |
      [Bedroom Box #2]
      |
      | Install a new run of NM-B 14/2 cable to power the smoke alarms
      |
      [Existing junction box with power]

      Nice work!

  6. chris May 22, 2013 at 8:28 am #

    Thanks Bob,
    Glad you were able to understand my explanation of what I did.
    So now I do have just one more question. Being that Bedrooms 2 and 4 only have 1 line each going to them, there is the unshielded ground wire in each box that is not connected to anything. What to do with the loose ends?
    On the other end of the lines, the grounds are connected in Hallway 1 and Bedroom 3. The new 14/2 power line is properly grounded as well.
    I do appreciate you help
    Chris

    • BobJackson May 22, 2013 at 7:02 pm #

      If the smoke alarm junction boxes are metal, the boxes must be grounded by connecting the NM-B ground wire to a #10-32 green ground screw fastened to the box. Use a ground wire pigtail from the ground screw and nut it to the NM-B ground wire as shown here.

      If your smoke alarm ceiling boxes are plastic, just fold the ground wire for an “end node” into the junction box with no connection as shown in this photo. Some plastic junction boxes may have a metal ground wire lug as a convenience for connecting several ground wires, for example the NM-B and ceiling fan ground wires.

      The reason metal junction boxes must be grounded is for shock protection in case a hot or neutral wire comes loose or is damaged and contacts the metal box. This would make an ungrounded metal junction box “hot” (energized with electricity) and a shock hazard if touched (your body becomes the electricity ground pathway!), whereas a properly grounded metal box will short the current to the ground wire and trip the circuit breaker to let you know something is wrong.

      Plastic junction boxes are non-conductive and therefore not grounded.

  7. Jonathan May 24, 2013 at 8:46 pm #

    Bob – first of all, kudos again on this page. The wiring diagrams were especially helpful.

    That written, I have one question for you. In Box 2 (Smoke Alarm in Unfinished Area) you spliced the wires, with one run ending in the basement and another run ending in the upper floors. From what I have read, you are “supposed” to wire these alarms in series, going from box to box, with only one end run – the last box on the line.

    Electrically speaking, if the alarm trips, current will flow through the traveler (red) wire to all of the boxes in your diagram. Therein lies my confusion – is there a reason why these installation guides only mention series runs and seem to discourage parallel runs?

    Thanks,
    Jonathan

    • BobJackson May 25, 2013 at 9:57 am #

      Hi Jonathan,
      The “daisy chain” wiring diagram illustrated in the Kidde/Firex smoke alarm datasheet and user manual are representative for ease of understanding. The wiring requirements stated by the manufacturer are:
      * A maximum of 24 Kidde devices can be interconnected in a multiple station arrangement.
      * The interconnect system must not exceed the NFPA (National Fire Protection Association)
      limit of 18 initiation devices, of which 12 can be smoke alarms.
      * Make certain all alarms are wired to a single, continuous (non-switched) power line,
      which is not protected by a ground fault interrupter.
      * A maximum of 1000 ft. of wire can be used in the interconnect system.
      * Use standard UL listed household wire (18 gauge or larger as required by local codes).

      The U.S. Consumer Safety Product Commission (www.cspc.gov) Directorate FOR Engineering Sciences published CONSIDERATIONS FOR INSTALLATION OF SMOKE ALARMS ON RESIDENTIAL BRANCH CIRCUITS which illustrates several wiring configurations. In particular, Figure 16 on page 19 in section 4.1 Dedicated Circuits and Smoke Alarms illustrates a splitting the smoke alarm wiring in a junction box T configuration at the 2nd floor.

      The junction box wiring configuration as I’ve used meets the wiring requirements, including:
      1. Interconnected alarms wired in parallel (pigtail connection to the alarms). The failure of a smoke alarm unit will not interfere with the remaining alarms.
      2. Single, continuous (non-switched) power line connection.

      The critical result is when I press the Test button on any of the 7 interconnected smoke alarms in my home (I tested every device); all the alarms sound in unison, but slightly out of phase like an echo as the other alarms respond to the trigger signal. What a racket! The dogs bark, wife and kids yell “Hey! What are you doing?!!”. I smile knowing that the system works correctly.

  8. Jonathan May 25, 2013 at 7:28 pm #

    Thanks, Bob, for the detailed explanation and the links. I am sure my wife and kids will have the same reaction when I test our system.

  9. Jonathan May 28, 2013 at 8:14 pm #

    Hey, Bob, quick update on what has happened. I wired my house in a similar manner to your wiring diagram: service entrance to a basement detector to first floor detector and basement to 2nd floor detectors. Thus, there was a parallel run, which was spliced in the basement, near the service entrance. The county inspector came, looked around, and gave me my close-in permit. Obviously, code enforcement is different everywhere, but this work passed. I fall under a modified NEC 2008 – thus an AFCI breaker for the run – and a modified NFPA 72. Thanks again for the advice. Jonathan.

    • BobJackson May 28, 2013 at 8:52 pm #

      > Thus, there was a parallel run, which was spliced in the basement, near the service entrance.
      The key requirement being the smoke detectors are all on the same circuit (via the basement junction box splice) for alarm signal continuity.

      > I fall under a modified NEC 2008 – thus an AFCI breaker for the run – and a modified NFPA 72.
      My home was built in 2002 prior to the updated NEC 2008 requirement for AFCI breakers for bedrooms, etc. and I’ve been replacing the older breakers in my panel with AFCIs. If you type “AFCI” in the search box at the top right HandymanHowTo.com page, you’ll find that I’m a believer in AFCIs.

  10. Wayne August 31, 2013 at 2:15 pm #

    Bob I have a very similar scenario as you depicted above. My home is a 1952 home in Washington DC that has no smoke alarms. I purchased 5 of the FireX PI2010 and will be installing them on 3 floors running them in line directly to a 15amp dedicated circuit/breaker.

    I am under the impression that the 18 gauge wire is preferable for installation of fire alarms. Have you heard mention of this and could you give some insight as to the rational behind the use of 18 gauge wire for smoke alarm installation.

    Any information you have would be of value. Thanks in advance.

    -Wayne

    • BobJackson September 3, 2013 at 6:10 pm #

      18 gauge wire is too small for use on a 15 AMP 120VAC circuit and would be:
      * A fire hazard!
      * Violate the National Electrical Code (NEC) and your local Building Code.

      The Kidde/Firex® PI2010 User Manual states:
      “The Make certain alarms are wired to a continuous (non-switched)
      power line. NOTE: Use standard UL listed household wire (as
      required by local codes)
      available at all electrical supply stores
      and most hardware stores.”

      The problem with 18 gauge wire is the ampacity, meaning “The current in amperes a conductor can carry continuously under the conditions of use without exceeding its temperature rating” is not rated for a 15 AMP circuit. Imagine the 18 gauge wire heating until it glows like toaster coils while melting and setting the house on fire.

      You should use a minimum of NM-B 14/2 (14 gauge) or optionally NM-B 12/2 (12 gauge) wire to comply with the NEC/Building Code requirements for a 15 AMP 120VAC circuit.

      While the PI2010 smoke alarm only draws 80mA (equal to 0.08 Amps) and the maximum of 24 interconnected alarms would only draw 1.92 Amps, so it would appear to work on 18 gauge wire, that not the point. The point is it violates the National Electrical Code (NEC)/Building Code because:
      * 18 gauge wire is too small for a 15 Amp circuit (ampacity rating).
      * the overcurrent protection provided by the 15 Amp circuit breaker would not protect the 18 gauge wire from overloading.

      250 feet of NM-B 14/2 wire costs about $50 at Home Depot as of this writing, which is a small price to pay for living safely.

      Also, if you were to sell the home, the home inspector would likely notice the odd looking 18 gauge wires connected to the circuit breaker panel and flag it as a “must correct” by a licensed electrician.

  11. Steve Hnath January 13, 2014 at 11:34 am #

    I replaced an old hardwired smoke detectors since the clips broke off to hold in in place. But when the electric was turned back on, all the other smoke detectors on the line are going off. I replaced the old one and everything works.

    • Bob Jackson January 13, 2014 at 6:09 pm #

      I’m not quite following your description. The smoke detector plastic mounting clips broke and you replaced it. When you turned on the electricity, all smoke detectors started beeping. Was the replacement unit defective?

  12. cw April 15, 2014 at 7:32 pm #

    If a smoke detector is still working but the mounting clips are broken, does it need to be replaced or is there some other way it can be clipped togeher?

    • Bob Jackson April 15, 2014 at 8:20 pm #

      You could try reattaching the smoke alarm to the trim ring with three small 1/4 inch squares of double-sided sticky tape. It’s a tradeoff between enough tape to hold the smoke alarm in place but not so much tape that it can’t be pulled off to replace the batteries or install a new unit some years down the road.

  13. Todd April 23, 2014 at 8:25 pm #

    Bob…I have a similar problem as CW. I have attempted to replace two of several smoke detectors in my house with Kidde Smoke/CO detectors. In my house, it is a hardwired, interconnected, non-switched system with NM-B 14/3 wires. When I reattached the new ones to power, all detectors in the house go into alarm state; not chirping. I have tried the units separately, but to no avail. I have returned them to the store and got two new ones. Same problem. If the two units are left out, the other detectors seem to work, but I would like to get these two locations back into service ASAP.

    I cannot find any information of a similar problem. Has anyone heard of such an issue?

    • Bob Jackson April 24, 2014 at 3:07 pm #

      Hi Todd,
      The new Kidde Smoke/CO detectors are probably incompatible with the existing smoke detectors in your home.

      You didn’t indicate the model # of the new Kidde detectors, but the Kidde PI2010 User Guide states:

      Kidde alarms and accessoriesCAN ONLY BE interconnected with other Kidde alarms and accessories
      as well as specified brands and models of interconnect compatible
      alarms. Connection of Kidde products to a non-specified manufacturer’s
      interconnect system, or connection with non-specified equipment
      from another manufacturer into an existing Kidde system could result
      in nuisance alarming, failure to alarm, or damage to one or all of the
      devices in the interconnect system. Refer to the User’s Guide supplied
      with each Kidde product for interconnect compatible models, brands,
      and devices.

      Thanks,
      Bob

  14. Joan McDermott August 15, 2014 at 4:50 am #

    Less than 40 days ago we had 8 brand new Kiddie smoke alarms installed by a professional. This was done because the alarms went off after they were serviced by the same professional, cleaning, new batteries, wiring checked, etc.
    Tonight, the alarms again went off, not all eight at first but one in the MBR, A very short while later they all went off.

    Do we have a major problem or what? Thank you,

    • Bob Jackson August 15, 2014 at 3:49 pm #

      If the alarms are correctly installed and wired, then it may be a environmental factor triggering the false alarms.

      Check the items in the User Manual for external causes. See Section 2. LOCATIONS TO AVOID and 5. NUISANCE ALARMS.

      > not all eight at first but one in the MBR
      Is the alarm in the master bedroom within 3 feet of the bathroom door (steam/humid air), too close to a heating/AC vent or a fluorescent light (electrical noise)?

  15. Andy Vitch August 21, 2014 at 8:16 am #

    I too have had issues with nuisance alarms in the kidde or garrison systems. I have suspected in the past that spiders or dust has triggered the alarm from locations in crawl spaces. I have a difficult one today. A series of 7 fired last night. I suspect, not 100% confident, the primary alarm going off is in a cathedral ceiling hallway. I am considering moving to a location out of the hallway where potentially there will be more air flow. Does this make sense to you? Do you have any other ideas? There was no shower/bath moisture issue as it was 3am but it was raining slightly outside and windows were open in the room.

    • Bob Jackson August 24, 2014 at 10:03 am #

      > There was no shower/bath moisture issue as it was 3am
      > but it was raining slightly outside and windows were open in the room.
      That could have been the problem due to condensation. The Kidde Knowledgebase states:

      “Your smoke alarm may sound when its very cold outside, or if a door adjacent to a heated area is opened, like in an entryway. This is due to condensation (water vapor) in the detection chamber. The sensor is a particle sensing device, when water condenses in the sensor the unit will go into alarm.”

      The FireX Alarm FAQ Answer for “What causes my FireX alarm to false alarm (alarm sounds when no smoke is present)?” lists several possible cause for nuisance or false alarms:
      * Age if the unit is over 8 to 10 years old
      * Location – near steamy areas (bathrooms/kitchens), in direct airflow near heating/cooling vents, dusty areas
      * Dust or insects in the sensing chamber
      * Cleaning solvents – especially ammonia

      Electrical interference from fluorescent lights is another cause.

      Also see: Preventing False Alarms by the City of Surrey.

      Thanks,
      Bob

  16. Wire Nut September 30, 2014 at 7:00 pm #

    A smoke alarm system should NEVER share a circuit with receptacles or lights. What if another yuck with no knowledge electrical safety disconnects the circuit for a reno or whatever? No protection. And pulling up plywood in the attic? What, did you get a deal on electrical work by the carpenter? Junction boxes are never allowed to be concealed, they have to be accessible. Most states the electrician has to be licensed and insured. We take code updates to renew licenses. And we have a responsibility to protect life and property. But if you want to put your safety in the hands of Joe Blow the carpenter or yourself who has to ask how to wire smoke alarms go for it.

    • Bob Jackson September 30, 2014 at 8:34 pm #

      Hi Wire Nut,
      I don’t understand the reason for your rant.

      Are you replying to the thread about Chris’ problem where he pulled up the attic floor plywood trace the wiring and locate the missing connection?

      > A smoke alarm system should NEVER share a circuit with receptacles or lights.
      Yes, I stated in the project:

      “In How to Install a Hardwired Smoke Alarm – Part 1 I described how the smoke alarm in the finished basement was disabled and improperly concealed in a ceiling crawl space in violation of the Building Codes.

      120VAC power for the smoke alarms will provided by a new branch circuit from an existing junction box on a continuous (i.e. non-switched) circuit (emphasis added in this reply). The new work is indicated by the green box in this wiring diagram

      Nor are any of the junction boxes concealed as shown in the project.

      Wire Nut wrote:
      > A smoke alarm system should NEVER share a circuit with receptacles or
      > lights. What if another yuck with no knowledge electrical safety disconnects
      > the circuit for a reno or whatever? No protection.
      You’re talking about several different issues. A smoke alarm must be connected to a non-switched circuit. Lights are controlled by a switch and agree with you. However, the statement about “receptacles” is just plain wrong.

      The NFPA 72®: National Fire Alarm and Signaling Code Handbook, 2013 Edition states in article 29.6.3(4) AC Primary Power Source:

      “AC primary (main) power shall be supplied either from a dedicated branch circuit or the unswitched portion of a branch circuit also used for power and lighting.”

      Take care not to confuse Fire Alarm requirements as commonly found in commercial buildings with interconnected smoke alarms in single family residential dwellings.

      Recall the National Electrical Code (NEC) is part of the National Fire Codes published by the NFPA.

      There is the possibility the local Authority Having Jurisdiction (AHJ) may have amendments requiring a residential smoke alarm be connected to a dedicated circuit. If you know of any, please cite references.

      The major change for residential smoke alarm wiring requirements is the 2008 NEC which requires it to be protected by an AFCI circuit breaker if it’s in a bedroom.

      Thanks,
      Bob

  17. Cole October 30, 2014 at 9:03 pm #

    This might sound like a silly question: is the fuse switch associated with connected smoke alarms the same one for ceiling lights? Thank you.

  18. brian October 31, 2014 at 11:29 am #

    Bob

    Your explanation to Wire Nut regarding the power source for Residential fire alarm smoke detectors seems to make a lot of sense.

    “AC primary (main) power shall be supplied either from a dedicated branch circuit or the unswitched portion of a branch circuit also used for power and lighting.” Although I prefer the latter of your statement

    In a nutshell if I have my smoke detectors connected to one of my bedroom circuits. I would know that power to my fire detection system is on (energized). Namely because the lighting and receptacles in that bedroom are working (energized).

    • Bob Jackson October 31, 2014 at 11:50 am #

      Hi Brian,
      I think Wire Nut (pseudonym) is an electrician by trade, which worries me because he’s clearly not up to speed the National Electrical Code (NEC).

      That quote you cited straight out of the NEC 2013 Handbook and it’s good advice.

      Thanks,
      Bob

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