Summary of the Article
1. Mains powered smoke alarms can be wired to the unswitched live feed of the nearest frequently used lighting circuit. This allows them to be connected to the mains power via the lighting circuit.
2. All smoke detectors are wired to a 120-volt household electrical circuit and have a battery backup. The battery backup ensures that the alarm still functions even if there is a power outage.
3. Fire alarm systems need a dedicated circuit for the fire alarm control panel. This circuit should not be used for lights, receptacles, or appliances. It must also be mechanically protected with an automatic disconnecting means.
4. It is a code requirement to connect smoke detectors to a GFCI (Ground Fault Circuit Interrupter) protected circuit. Smoke alarms can also be AFCI (Arc Fault Circuit Interrupter) protected.
5. The maximum number of hardwired smoke alarms that can be installed is dictated by the National Fire Protection Association (NFPA). The maximum quantity is 12 smoke alarms, with an additional 6 devices such as CO alarms, relay devices, heat alarms, strobes, or auxiliaries.
6. Smoke detectors should be positioned at least 300mm away from walls and light fittings/decorative objects. This is to ensure effective circulation of air and to prevent obstructions from obstructing the sensor chamber.
7. Smoke detectors are connected to each other through a red wire. When any alarm detects a fire, it sends a 9-volt signal on the red wire, triggering all interconnected alarms to sound their alarms.
8. A two-wire smoke detector circuit requires the power to be cut when an alarm occurs.
Questions and Answers
1. Can you wire a smoke alarm to a lighting circuit?
Yes, it is possible to wire mains powered smoke alarms to the unswitched live feed of a frequently used lighting circuit.
2. What circuit are smoke detectors wired to?
Smoke detectors are wired to a 120-volt household electrical circuit, with a battery backup for power during outages.
3. Does a fire alarm system need a dedicated circuit?
Yes, a fire alarm control panel requires a dedicated branch circuit that is not used for lights, receptacles, or appliances.
4. Is it a code requirement to connect smoke detectors to a GFCI protected circuit?
Yes, smoke alarms can be connected to a GFCI (Ground Fault Circuit Interrupter) protected circuit as per code requirements.
5. How many smoke alarms can you have on a circuit?
The National Fire Protection Association (NFPA) allows a maximum of 12 smoke alarms to be installed, along with 6 additional devices.
6. How far should a smoke detector be from a light?
A smoke detector should be positioned at least 300mm away from walls, light fittings, and decorative objects to avoid obstruction and ensure efficient sensing.
7. What are smoke detectors connected to?
Smoke detectors are connected to each other through a red wire. When one alarm detects a fire, it sends a 9-volt signal on the red wire to trigger all interconnected alarms.
8. What is a two-wire smoke detector circuit?
A two-wire smoke detector circuit requires the power to be cut when an alarm is triggered.
Can you wire a smoke alarm to lighting circuit
Can mains powered smoke alarms be connected to the mains power via the lighting circuit Yes, hard-wired mains powered alarms can be wired to the unswitched live feed of the nearest frequently used lighting circuit.
What circuit are smoke detectors wired to
All the units are wired to a 120-volt household electrical circuit and each have a battery backup. The battery backup provides extra protection by powering the alarm even if a fire causes the household power to go out. It's important to learn how to install a hard-wired smoke detector yourself.
Cached
Does a fire alarm system need a dedicated circuit
The fire alarm control panel must receive its power from a dedicated branch circuit. The circuit cannot be used for lights, receptacles, or any type of appliances. The circuit must be mechanically protected: meaning it has to be provided with an automatic “disconnecting means” (commonly called a “circuit breaker”).
Is it a code requirement to connect smoke detectors to a GFCI protected circuit
A smoke alarm can be AFCI and or GFCI protected so the answer is yes. Code exempts fire alarm systems installed to code NEC 210.12. A.
How many smoke alarms can you have on a circuit
What's the maximum amount of hardwired smoke alarms I can install The National Fire Protection Association (NFPA) dictates a maximum quantity of 12 smoke alarms with up to 6 additional devices (CO alarms, relay devices, heat alarms, strobes, or auxiliaries).
How far should a smoke detector be from a light
300mm away
It is recommended to position the alarm at least 300mm away from walls and light fittings/decorative objects (See fig 1.). This is because air does not circulate effectively in corners, and objects like light fittings can obstruct smoke and heat from entering the sensor chamber.
What are smoke detectors connected to
The electrician runs the red wire from alarm to alarm to interconnect them. When any alarm detects a fire, it sends a 9-volt signal on the red wire. Any alarm that detects a 9-volt signal on the red wire will begin sounding its alarm immediately.
What is a 2 wire smoke detector circuit
Either of these smoke detectors. Actually need their power to be cut when an alarm occurs. So that they can reset. On a two wire smoke detector. If you have it connected to a vista alarm system zone.
What is the NEC code for fire alarm circuits
According to NEC Articles 760 and 725, there are two types of fire alarm system circuits: power restricted and non-power limited. Power Limited Fire Alarm Wires typically work at 24 volts DC, whereas non-power limited cables run at 120 volts AC.
What type of circuit would be used for a fire alarm
Based on the type of detectors and FACU, the signals can be sent over an initiating device circuit (IDC) for conventional systems, or a signaling line circuit (SLC) for addressable systems.
Can a smoke detector be on a GFCI breaker
Based on current requirements in Rule 32-110 (CE Code 2015), however, smoke alarms are not permitted to be supplied by a branch circuit protected by a ground/arc fault circuit interrupter (GFCI/AFCI) because, during a fire situation, the interrupter may trip and potentially disable the smoke alarm.
Does the smoke detector circuit need to be on an AFCI breaker
AFCI is required, but not GFCI, modulo local amendments
As an aside, NFPA 72 29.9. 4 point 5 requires smoke alarms that are AFCI or GFCI protected to have battery backup power.
What does the NEC say about smoke detectors
Activation of a smoke detector in a dwelling unit or sleeping unit shall not activate alarm notification appliances outside of the dwelling unit or sleeping unit, provided that a supervisory signal is generated and monitored in accordance with Section 907.6.
How close can a smoke alarm be to a light
i) within 300mm of a corner of a ceiling and a wall; ii) within 300mm of a light fitting; iii) within 400mm of an air-conditioning vent; or iv) within 400mm of the blades of a ceiling fan.
What is the NFPA 72 0.7 rule
NFPA 72 requires that all points on the ceiling have a detector within a distance of 0.7 times the listed spacing of the detector. This ensures that when detection is used, the entire space on the ceiling is covered by detection. This requirement is commonly called the Point 7 (0.7) Rule.
What is code for smoke detector from the ceiling
Wall-mounted alarms should be installed not more than 12 inches away from the ceiling (to the top of the alarm). If you have ceilings that are pitched, install the alarm within 3 feet of the peak but not within the apex of the peak (four inches down from the peak). Figure A. 29.8.
How do you add a smoke detector to an existing circuit
How to Install Wired Smoke DetectorsTurn Off the Power. Find the existing circuit on your home's circuit breaker that powers your smoke detectors.Cut the Holes.Run the Wire.Attach the Wires to the Electrical Boxes.Secure the Electrical Boxes.Wire the Smoke Detector.Put It All Together.Connect to the Circuit.
Do smoke detectors need to be hardwired
What Does the Hard-Wired Smoke Alarm Ordinance Require Since 1973, the State building code has required that all new homes be provided with a hard-wired smoke alarm. And since March 20, 1995, a hard-wired smoke detector with battery back-up is required outside the sleeping area of the home.
Can a 2 wire smoke detector be connected to the switch power connection
The first smoke detector is connected to the power supply using a 2-wire connection. A wall switch or outlet, circuit breaker panel, or light fixture with pass-through cables can all serve as power source. The smoke detectors are then connected one after the other using 3-wire wires.
Do smoke detectors need 3 wires
If multiple smoke detectors are being installed, your electrician will run a 3-wire cable (with ground) from the first smoke detector to each subsequent smoke detector. The extra wire allows the smoke detectors to communicate with one another so that if one smoke detector detects smoke, all detectors will go off.
Do smoke detectors need to be on a dedicated circuit NEC
Residential smoke alarms should be wired on a dedicated circuit. It's a good idea to have at least one light or receptacle-on the same circuit, to alert the homeowners in case the circuit breaker ever trips. Interconnected alarms are usually wired in a daisy chain, using 14-3 or 12-3 cable.
Where do you put smoke detectors in NEC code
Install smoke alarms inside each bedroom, outside each sleeping area and on every level of the home, including the basement. On levels without bedrooms, install alarms in the living room (or den or family room) or near the stairway to the upper level, or in both locations.
What are the six types of circuits that may be connected to a fire alarm panel
Signalling Line Circuits (SLC)Smoke detectors.Heat detectors (Rate of Rise and Fixed Temperature)Manual call points or manual pull stations.Notification appliances.Responders.Fire sprinkler system inputs.Switch status. Flow control. Pressure. Isolate. Standard switches. Monitor modules.
Which class of wiring in a smoke detector circuit requires the use of an end of line resistor
Class B conventional circuits
Class B conventional circuits go through all devices and terminate in an end of line resistor (EOLR), which provides electrical supervision of the circuit.
Do smoke alarms need to be on an arc fault breaker
AFCI is required, but not GFCI, modulo local amendments
4 point 5 requires smoke alarms that are AFCI or GFCI protected to have battery backup power.
