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Kevin, Licensed Electrical Contractor
Category: Electrical
Satisfied Customers: 3729
Experience:  30 years Licensed Electrical Contractor in Illinois, Adjunct College Electrical Instructor, Former Electrical Inspector, Diploma: Digital Electronics, FCC Technician License
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My daughter and son-in-law just moved to a new house. The

Customer Question

Hi I'm Bob. My daughter and son-in-law just moved to a new house. The sellers added hard wired smoke detectors. The system is brand new. Last night she said it went off at 1:00 in the morning for no apparent reason. They checked all units and when they went to the attic and checked that unit the system silenced. Is it too hot?
Submitted: 2 years ago.
Category: Electrical
Expert:  Kevin replied 2 years ago.
Hello name is ***** ***** I will be happy to assist you with your electrical question. My goal is to exceed your expectations on Just Answer!
Shown below are the various reasons why smoke alarms will go into alarm or chirp mode:
Heat has nothing to do with the smoke alarms being triggered unless they are a heat sensing alarm that is connected to a fire alarm/security alarm system.
Often, the problem is caused by a loose wire connection and/or a low battery. Even though the system is hard wired, they may also contain a battery backup.
Why can smoke alarms go into alarm when no smoke is present?
Any of these situations can cause unwanted alarms:
A) Cover or sensor chamber is covered by dust or dirt.
Alarms may look clean, but dust can accumulate inside the cover, especially in newly built
homes. Gently vacuum smoke alarms regularly using the soft brush attachment.
B) Insects covered or clogged the sensor chamber.
C) Alarm was triggered from another part of the home.
In a system of interconnected AC or AC/DC alarms, the unit triggering the alarm is in another
part of the home - smoke may be present, but you can't see it.
D) Power interruptions to AC/DC smoke alarms.
Smoke alarms may alarm briefly when power is interrupted, then restored. Power interruptions are common in areas where utility companies switch grids in the early hours of the morning.
E) A loose electrical connection on AC or AC/DC smoke alarms. In AC or AC/DC smoke alarms, a loose hot wire connection can intermittently disconnect power to the smoke alarm. The effect is the same as a power failure. When power is restored, the units may alarm briefly. Note: A loose or disconnected neutral wire may cause the alarm to chirp or go into alarm. For residential applications, connecting stranded 18 AWG wire from the smoke alarm to solid 14 AWG wire can be difficult. Be sure wire is making a reliable connection.
F) When the furnace is turned on for first use:
Oil and residue is present on and in furnaces and ductwork from the factory to protect the metal surfaces. This can cause smoke to be emitted for a period of time and possibly set off smoke alarms.
G) Dirt, drywall dust and construction debris is often present in ductwork. First use of the furnace can cause fine particles to be blown through the house possibly causing nuisance alarms. This is why the homeowner may be in the house for several months without incident and why nuisance alarms tend to increase during the Fall.
H) Humidity - Ionization smoke alarms are more susceptible to nuisance alarms when placed near a
bathroom or other potentially high humidity area.
I) Near Cold Air Returns
Smoke alarms placed near a cold air return are more susceptible to nuisance alarms because dusty air can be blown through the alarm sensing chamber.
J) Smoke alarm may need to be relocated.
If possible, install smoke alarms at least 20 feet from appliances like furnaces and ovens, which produce combustion particles. Alarms should be at least 10 feet from high humidity areas like showers and laundry rooms, and at least 3 feet from heat/AC vents and fluorescent
lights whenever possible. In areas where a 20-foot (6 meter) distance is not possible – in modular, mobile, or smaller homes, for example – it is recommended the Smoke Alarm be placed as far from these fuel-burning sources as possible. The placement recommendations are intended to keep these Alarms at a reasonable distance from a fuel-burning source, and thus reduce “unwanted” alarms. Unwanted alarms can occur if a Smoke Alarm is placed
directly next to a fuel-burning source. Ventilate these areas as much as possible.
Why do smoke alarms chirp intermittently?
A) The "chirp" will only be caused by issues surrounding the battery or miss wiring. However, a homeowner may confuse the chirp with an intermittent alarm. Try and get the homeowner to be specific as to what they are hearing. A “chirp” will have a higher pitched tone and sound in equal
intervals about once every minute. An intermittent alarm will be random, sound usually for several seconds and have a lower pitched tone. Any of these situations can cause unwanted chirps:
B) Battery pull-tab is still in the alarm.
The battery pull-tab must be removed after AC power is
provided to the alarm.
C) The Battery Drawer is open.
The battery drawer must be completely closed for the
battery to make contact with the terminals.
D) Low battery.
As the battery in a smoke alarm becomes weak, the smoke alarm will "chirp" about once a minute to alert you that the battery needs to be replaced. Note: Only the alarm with a low battery will chirp. No signal is sent through the
interconnect wire. The other alarms will be
E) Battery is present but part of the terminal is obstructed. The battery may not be fully making contact with the terminals in the alarm. Check to be sure the battery pull-tab or some other obstruction is completely removed.
F) Why does the alarm chirp when power is disconnected and the battery is removed?
The circuitry of the alarm contains capacitors that store energy. You must press and hold the test button to dissipate the capacitor. You will hear a steadily weakening sound until it is silent.
Hope this helps………If you have any additional questions, let me know and I’ll be glad to answer them for you.
Otherwise, don’t forget to rate me before you log Off.
The next time you have an electrical question, you can also request for me at: ……….Thanks…………..Kevin!
Expert:  Kevin replied 2 years ago.
If you have any additional questions, let me know and I’ll be glad to answer them for you.
Otherwise, don’t forget to rate me before you log Off.