Ten to Twelve Pieces. The National Electrical Code (NEC) does not specify how many smoke detectors can be installed in a 15-amp circuit, but does state that the total load on the circuit should not exceed the circuit’s rating. For a 15 amp circuit, the total load should not exceed 15 amps (or about 1800 watts).
Theoretical Value
Typically, smoke detectors use a current of 0.3 to 0.5 amps each. In other words, if we have only detectors connected, a 15-amp circuit could theoretically support 30 to 50 smoke detectors. However, this is only a rough estimate. And, it does not take into account other factors such as the distance between wires, other equipment or detectors.
Practical Suggestion
In practice, we suggest not to have too many smoke detectors on the circuit to avoid overload. It is usually recommended to limit the number of detectors to 10 to 12. This ensures that the circuit is not loaded for reliability. Overloading can lead to potential electrical hazards.
