This project is continued from Part 1.
Kidde/Firex® 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.
Kidde/FIREX Smoke Alarm Model # PI2010
The alarm includes the 9 volt battery – a nice touch to get started.
Smoke Alarm Wiring Diagram
In Part 1, I described how the smoke alarm in the finished basement was disabled and improperly located in a crawl space. The scope of work for this project is to:
- Remove the old smoke detector and ceiling electrical box.
- 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:
Smoke Detector Wiring Diagram
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 goes off, 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 that you hire a licensed electrician to do the work.
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
Smoke Alarm Installation Tools
NM-B 14/3 and 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 wire 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. 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 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).
NM-B 14-3 versus NM-B 14/2 Wire
For brevity, I use “NM” when referring to “NM-B” in this project. I also use the terms “wire” and “cable” somewhat interchangeably. Cable generally refers to the entire NM-B wire bundle, and wire refers to an individual conductor.
Unfinished Basement Smoke Alarm Installation
I began by removing the old smoke alarm and ceiling box from the crawlspace in 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 14/3 wire that interconnects to the the other smoke alarms in the house.
Basement Smoke Alarm Installation: New Location
Smoke Alarm Ceiling Junction Box Wiring
An octagonal 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 14/2 for power and NM 14/3 for the second smoke alarm to be installed in the finished basement area.
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 octagonal box because it can handle four cables without over crowding.
Smoke Alarm Octogonal Ceiling Box Wiring
The above photo corresponds to these cables in the wiring diagram:
Smoke Detector Octogonal Wiring Diagram
The wires are matched by color, twisted 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 the National Electrical Code (NEC).
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 Wiring: Ready for the Smoke Alarm Trim Plate
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
The smoke alarm is mounted to the trim plate by twisting on until it ratchets into place.
120VAC Branch Circuit Wiring for Smoke Alarm
A new run of NM 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 behind a light switch.
The new circuit for the AC power feed installed in the next step is highlighted in this portion of the wiring diagram:
Smoke Detector AC Branch Circuit Wiring Diagram
Be certain to shut off the circuit breaker and confirm the circuit is dead with your voltage detector before continuing!
The new NM 14/2 cable run for the smoke alarm power feed is brought into the existing junction box and wired in as shown below. Remember to secure your new cable with wire 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 Circuit Wiring
If you don’t have a junction box to wire into, you can splice into an existing circuit as explained in this project.
Jumping ahead to when I’ve installed the 2nd smoke detector and completed all the wiring, the green AC power indicator glows when the alarm is on 120VAC power. For now, the circuit breaker and AC power must remain off.
Kidde PI2010 Smoke Alarm: Green LED AC Power Indicator
Now I’m ready to install a second smoke detector in the finished section of the basement in Part 3.
Thanks for reading,
Bob Jackson
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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?
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.
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
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
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.
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
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
> 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!