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A comprehensive guide on replacing hardwired (and battery powered) smoke detectors
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Functioning smoke detectors are extremely important in maintaining the safety of your home. Smoke detectors need to be replaced every 10 years, and smoke detector batteries should be replaced every 6 months. [1] X Trustworthy Source National Fire Protection Association Nonprofit organization devoted to eliminating death, injury, property and economic loss due to fire, electrical and related hazards. Go to source You may need to replace your smoke detector The process takes just a few minutes and only requires a screwdriver and some electric tape.
How to Remove & Change a Smoke Detector
Cut the power to your home at the circuit breaker. Then, twist the smoke detector counterclockwise to remove it from the mounting. Pull out the wire harness and unhook the wires. Connect your replacement wires following the color coding and reinstall the detector in the mount.
Steps
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Shut off the electricity using the circuit breaker. Find your circuit breaker and switch off power to the smoke detector in question. This will remove the danger of electric shock resulting from touching open wires. [2] X Research source
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Remove the old detector from the mounting. Try to rotate the detector about a quarter-turn counterclockwise to remove it. If it doesn’t move, look for a depressed tab and press while turning it. The unit will now be suspended from the ceiling by three wires, all connected to the detector via one plug called the wiring harness. These wires are:
- Black - 120 volts
- White - Neutral
- Red or Yellow - Interconnect (this is the wire that connects the alarm with the remaining alarms in your residence)
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Unhook the wire harness from the detector. Squeeze both sides of the plastic plug while pulling the plug away from the detector. The old detector should now be completely detached.
- In the rare event that the smoke alarm is one of the super old models that has no harness, cut and strip the wires connecting the smoke alarm.
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Remove the mounting plate. Take a screwdriver and remove the two screws that hold the mounting plate to the electrical box in your ceiling. Be careful not to accidentally pull the wires out of the ceiling while removing the mounting plate.
- It’s always worth checking to see if the existing mounting plate will work with your new unit before you replace it.
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Remove the wiring harness. Start by removing any electric tape or wire caps that are attached to the wiring harness. Untwist the wires and remove the wiring harness. The three wires in the ceiling should now just be exposed metal ends. [3] X Trustworthy Source National Fire Protection Association Nonprofit organization devoted to eliminating death, injury, property and economic loss due to fire, electrical and related hazards. Go to source
- Even if you’re replacing a smoke alarm with an identical model, it’s best to not reuse the old wiring harness. It’s rare, but it’s possible the manufacturer changed the amperage or current rating of the harness for their newer models.
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Attach the new wiring harness to the wires in the ceiling. The new smoke detector should also come with a wiring harness very similar to the one you removed. Match the wires using the color coding and attach them by twisting the metal ends around each other. Wrap the newly attached metal ends in electric tape or attach a wire cap. Attach the wires in the following manner: black to black, white to white, and red or yellow to the color of the third wire in your ceiling (this color can vary). [4] X Trustworthy Source National Fire Protection Association Nonprofit organization devoted to eliminating death, injury, property and economic loss due to fire, electrical and related hazards. Go to source
- After attaching the wires, pull down slightly on the wire harness to make sure you have a good connection that can support the weight of the alarm. If the wire harness comes undone you will need to reattach the wires, making sure to wrap them tightly around each other.
- If there are only two wires, you only need to attach black to black and white to white.
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Attach the new mounting plate. Take the new mounting plate that came with the new alarm and pass the wiring harness through the large hole in the center of the plate. Then screw the plate into the ceiling/wall with the two screws that you removed earlier.
- You can do this before attaching the new wire harness if you’d like.
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Connect the new smoke detector to the harness. Plug the wiring harness into the new detector, and then attach the smoke detector to the mounting plate. This can most likely be done by holding the detector up on the mounting plate and turning the detector clockwise. [5] X Trustworthy Source National Fire Protection Association Nonprofit organization devoted to eliminating death, injury, property and economic loss due to fire, electrical and related hazards. Go to source
- If your smoke detector has a backup battery (which most do these days), don’t forget to install new batteries before you attach it to the mounting plate.
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Turn on the electricity and check your work. Flip the circuit breaker back on. All smoke detectors have a “test” button (sometimes it is the only button on the face of the detector). Press and hold the button for at least 5 seconds, and you should hear a beep. [6] X Trustworthy Source National Fire Protection Association Nonprofit organization devoted to eliminating death, injury, property and economic loss due to fire, electrical and related hazards. Go to source
- If you have other working smoke alarms in the house, they may all beep. This is a sign that you connected your new smoke alarm properly.
- If the smoke detector does not beep when tested, check that you matched the wires properly and that they are sufficiently attached at the metal ends. Check the circuit breaker to make sure the power is on.
- You can use an aerosol can of smoke to perform a real test of the detector, if desired.
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Locate all of your smoke detectors. There should be at least one detector on every floor of the house, including finished attics or basements. You may even have multiple smoke detectors on each floor, so make sure to check every room.
- If you notice you’re missing a smoke detector on a floor, install one!
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Check the manufacture date and replace ancient detectors. The location of the manufacture date should be easy to find but varies by model. If you find a smoke detector that is over 10 years old, replace it immediately. If you can't find a manufacture date on the smoke detector, the detector is probably over 10 years old anyway and should be replaced. [8] X Research source
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Test your smoke detectors monthly to ensure they work. Find the button on the face of the detector and hold it for at least 5 seconds. If the smoke detector beeps, it is functioning properly. If the detector does not beep, something is wrong. [9] X Trustworthy Source National Fire Protection Association Nonprofit organization devoted to eliminating death, injury, property and economic loss due to fire, electrical and related hazards. Go to source
- You may hear all of your smoke alarms beep while only testing one of them; this is normal, and indicates the smoke detector in question is functioning properly.
- You can buy an aerosol can of smoke to test your detector if you wish.
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Use the right type of smoke detector for your space. Deciding on a smoke detector is mostly personal preference, but there are some features to know about. [10] X Trustworthy Source National Fire Protection Association Nonprofit organization devoted to eliminating death, injury, property and economic loss due to fire, electrical and related hazards. Go to source
- Some newer smoke detectors also function as a carbon monoxide detector. If you don’t have a CO detector in your house, this is a good option. It is only necessary if you use gas in the house.
- Wireless smoke detectors are convenient, but they can only connect to other wireless alarms of the same model. If you’re replacing all of the smoke detectors in your house and choose the wireless option, make sure to purchase the same make and model.
- Check the manufacture date. Since smoke alarms have a fairly static 10-year lifetime, buying one that has been on the shelf for two years will only give you 8 years of use.
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Expert Q&A
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QuestionCan I use the existing wire harness to connect the new smoke detector?Mark Spelman is a General Contractor based in Austin, Texas. With over 30 years of construction experience, Mark specializes in constructing interiors, project management, and project estimation. He has been a construction professional since 1987.Yes, you can, as long as it has 2 wires with a ground.
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QuestionCan I keep and reuse the old harness with my new smoke detecter?Mark Spelman is a General Contractor based in Austin, Texas. With over 30 years of construction experience, Mark specializes in constructing interiors, project management, and project estimation. He has been a construction professional since 1987.Yes, you do not have to replace the house wiring.
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References
- ↑ https://www.nfpa.org/education-and-research/home-fire-safety/smoke-alarms/changing-clocks-and-batteries
- ↑ https://www.getprepared.gc.ca/cnt/rsrcs/sfttps/tp201011-en.aspx
- ↑ https://www.nfpa.org/education-and-research/home-fire-safety/smoke-alarms/installing-and-maintaining-smoke-alarms?l=841
- ↑ https://www.nfpa.org/education-and-research/home-fire-safety/smoke-alarms/installing-and-maintaining-smoke-alarms?l=841
- ↑ https://www.nfpa.org/news-blogs-and-articles/blogs/2023/03/06/what-kind-of-smoke-alarm-smoke-detector-should-i-buy
- ↑ https://www.nfpa.org/news-blogs-and-articles/blogs/2023/03/06/what-kind-of-smoke-alarm-smoke-detector-should-i-buy
- ↑ https://www.nfpa.org/education-and-research/home-fire-safety/smoke-alarms/changing-clocks-and-batteries
- ↑ https://www.tdi.texas.gov/tips/smoke-alarms-where-to-put-them-how-often-to-replace-batteries.html
- ↑ https://www.nfpa.org/news-blogs-and-articles/blogs/2020/08/17/how-do-i-maintain-my-smoke-detector
About This Article
Article Summary
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Before you replace a smoke detector, you should switch off the circuit breaker for the smoke detectors to avoid electrocuting yourself. To remove your old smoke detector, twist it counterclockwise and disconnect its wires by squeezing the plastic plug. Then, you’ll need to unscrew the mounting plate and disconnect the wires from it. Screw your new mounting plate in its place and attach the new smoke detector. Give your smoke detector a quick test and you’re good to go! For more tips from our Electrical co-author, including how to work out if your smoke detectors need replacing, read on!
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"Very informative. Breaking down the instructions into steps was a great idea. Using both words and pictures is helpful, especially if someone is a visual learner. Videos provided extra information that you could skip if you didn't need more information."
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