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Do Smoke Detectors Need Dedicated Circuit? (Answered)

Smoke detectors are a must-have item in our houses, offices, and properties. The smoke detectors turn on the alarm when a fire is detected in the building, helping us evacuate during a fire.

As a result, you might be wondering if smoke detectors require dedicated circuits to operate flawlessly. You might also want to know if interconnected smoke detectors can be connected on different circuits.

Let’s find the answers to all your queries regarding the circuit of smoke detectors.

Do smoke detectors need a dedicated circuit?

The smoke detectors in residential properties should be on a dedicated circuit. You should also wire a light onto the same circuit as the smoke detector so that you can immediately detect if the circuit breaker trips. The interconnected smoke detectors are connected in a daisy chain.

Smoke detectors are the most important device in any building. It basically alarms the residents in the building in case of a fire by detecting the smoke.

The smoke detectors should be connected to dedicated circuits for flawless functioning. However, you can connect other small electrical appliances to that circuit.

There are multiple reasons why a smoke detector should be connected to a dedicated circuit. One of the most vital reasons is that if all the smoke detectors are connected on the same circuit on a floor.

And if that circuit’s breaker trips, the whole smoke alarm system of the floor will be dysfunctional.

Although you can connect lights on the same circuit in which all the smoke breakers are connected, it will take time to replace the circuit breaker.

In the meantime, if a fire breaks down in the building, the smoke detector won’t be able to notify the people on the floor.

As a result, connecting the smoke detectors on the same circuit can result in major accidents. Putting the smoke detectors on a separate circuit will prevent the smoke alarms from getting deactivated at the same time.

Smoke detectors need dedicated circuits to operate at their full capacity. If the smoke detectors are connected on separate dedicated circuits, they will get an adequate amount of electricity.

Connecting smoke alarms on a dedicated circuit will also make sure that the circuit breaker doesn’t trip frequently.

This is due to the fact that a smoke detector won’t draw more electric current than what the circuit can handle. As a result, the smoke detector will last for a long period of time on a dedicated circuit.

If you connect smoke detectors on a dedicated circuit, you should also keep a low powered light on that same circuit. This will help you to almost immediately detect if the circuit breaker trips.

Let’s take a detailed look at why you should connect smoke detectors that need a dedicated circuit.

All the smoke detectors won’t become dysfunctional together:

If the smoke detectors are connected to the same circuit, all of them can get dysfunctional at the same time if the circuit breaker trips. It can result in serious accidents if all the smoke alarms turn off at the same time.

A smoke detector will get enough electricity:

When the smoke detector is connected on a dedicated circuit, it will get enough electricity to operate properly. It will make the smoke detectors very effective and error free.

The circuit breaker won’t trip frequently:

If more than one smoke detector is connected to one circuit, it can trip frequently due to over current flow. As a result, by putting a smoke detector on a dedicated circuit you can prevent frequent circuit breaker tripping.

What circuit do smoke detectors go on?

Smoke detectors are directly powered to AC electrical circuits. The circuits that are used for smoke detectors are usually dedicated circuits that only powers up that specific smoke alarm.

Numerous individuals include a battery backup system to keep the smoke alarm functional when there is a power outage in your building.

The smoke detectors are also connected to the lightning circuit. The alarm should sound and function properly, indicating that the battery of the smoke detector is in good condition.

If the detector doesn’t operate and respond, the battery should be replaced as soon as possible. You should change the batteries of the smoke detectors every once in a while.

While connecting a smoke detector to a circuit, you should make sure to connect the wires correctly. If the wiring is done incorrectly, the smoke detectors will cause false fire alarms and the unit can also get damaged.

Can you wire smoke alarm to lighting circuit?

You can definitely wire a smoke alarm to the lighting circuit. Wiring smoke detectors to lighting circuits will save you a lot of money as it ensures cost-effective usage of cables.

You can wire smoke alarms to lighting circuits in one of two ways: through loop-in ceiling roses or through junction boxes. Among them, the loop-in technique is mostly used as it provides economical wire usage.

Lighting circuits, unlike power circuits, are usually circular in nature. This circuit comes handy in buildings that require a huge amount of smoke detectors as it is a cost effective method.

How many smoke detectors can you put on one circuit?

The number of electrical appliances allowed in one circuit breaker is 18. However, according to NFPA 72 guidelines, the maximum number of smoke detectors that you can put on one circuit is 12.

Before connecting the smoke detectors, always double-check that the units you’re attaching are compatible with each other.

Along with the 12 smoke detectors, you can also attach up to six suitable small electrical devices in that one circuit. The compatible devices attached with the smoke detectors will help you to immediately detect when the circuit breaker trips.

Can interconnected smoke detectors be on different circuits?

No, interconnected smoke detectors should not be on different circuits. The wiring of the interconnected smoke detectors should be on the same circuit.

However, only 12 interconnected smoke detectors can be connected on the same circuit.

A circuit has a capacity of connecting 18 electrical appliances or devices. However, according to the electrical code for smoke detectors, only 12 interconnected smoke detectors should be on the same circuit.

All of the interconnected smoke detectors must be powered by the same circuit breaker. The total length of wire used to link the interconnected smoke detectors should not be more than 300 meters.

The interconnected smoke detectors are quite useful in buildings that remain busy most of the time.

This is due to the fact that when one smoke detector in interconnected smoke detectors turns on, all the smoke detectors will activate making the alarm clearly audible.

What is the NEC code for smoke detectors?

Understanding or knowing the NEC code for smoke detectors is very important to install them in the right way.

If you don’t follow the NEC code for smoke alarms, the smoke detectors will provide false alarms, and the device can also get permanently damaged.

There are multiple codes for smoke detectors that are imposed by NEC for safe and effective installation. Let’s take a look at the NEC code for smoke detectors.

Location of installation:

The NEC states that smoke detectors should be installed in all sleeping rooms of the building that are not previously wired for smoke detection.

Outside of each distinct sleeping area, such as in the corridor outside the bedrooms, and on each level of a multi-story dwelling, smoke detectors (alarms) must be installed.

Battery backup:

The smoke detectors should have a battery backup so that they function even when the power is interrupted.

This NEC code is very important as with battery backup the smoke detectors will alarm the residents in case of fire during power outage.


ACcording to NEC, the smoke detectors in a floor should be interconnected with each other. This is due to the fact that when the smoke detectors are interconnected, all of the fire alarms will activate if one of them activates.

With all smoke detectors interconnected, the smoke alarm will be clearly audible in all bedrooms over background noise.

Number of smoke detectors connected in a circuit:

According to the NEC code for smoke detectors, more than 12 smoke detectors shouldn’t be wired into one circuit.

The 12 smoke breakers should be connected in the same circuit breaker. With the 12 smoke breakers, you can also connect 6 low electricity consuming devices.

Final Thoughts

The smoke detectors do not necessarily need a dedicated circuit. However, you can most definitely connect a smoke detector in a dedicated circuit. It will keep the smoke detection active even if one circuit breaker trips. You can also  connect up to 12 connected smoke detectors in a single circuit.