It is assumed that the power circuit is for the fire alarm system, and it's also assumed that the associated wiring is installed with electrical safety in mind. The question here, though, about the requirements for a dedicated circuit, without any GFCI or AFCI protection, is based on fire-life safety.
GFCI and AFCI Exception
We'll start with the GFCI and AFCI exception. Electrical safety is based on protecting people and property from electrocution and the possibility that the wiring will start a fire. In recent years, Ground Fault Circuit Interrupters (GFCI) and Arc Fault Circuit Interrupters (AFCI) have been included in the Code for people and property protection.
Fire-life safety, though, is based on electrical safety, and added to electrical safety is fire-alarm life safety.
Ground Fault Circuit Interrupters and Arc Fault Circuit Interrupters are automatic devices. If a ground fault or arc fault is detected by the circuit breakers, no one has to take action, the circuit breaker just turns off the power. There is no announcement to the building owner or management that the power is turned off, the management or owner can figure that out for themselves.
Because of fire-alarm life safety concerns, though, the fire alarm system has to be powered on at all times; the breakers should never just automatically turn themselves off.
So that the power is not just turned off automatically, the fire alarm system cannot have an automatic GFCI or AFCI in the power system. This includes the 20-amp branch circuit, and all circuit breakers between the power pole outside and the branch circuit.
In essence, the power for a fire alarm control panel, and any fire alarm power supply or other fire alarm equipment should never automatically turn off.
Dedicated Circuit Breaker
No one should be able to turn off the power to the fire alarm system without knowing that it's the fire alarm system that is being turned off.
The actual rule in the code specifies that anyone having access to the system needs to be authorized. In other words, the owner or management of the building should have control over the person that can turn off the fire alarm system. That's the reason for the lock on the room door and the lock on the panel itself.
Going one step further, often a clip is applied to the handle of the circuit breaker to remind even the authorized people to not turn off the fire alarm system, unless there is a real good reason to turn it off.
To make sure everyone knows about the fire alarm related breakers (including the firefighters), the circuit breaker needs a red marking. It also has to be very carefully labeled to show the authorized person that leaving power on to the fire alarm system is important.
Branch Circuit Other Load Exclusion
Automatic Power Shutoff
- When other devices, like building entry heaters, lighting systems, or wall outlets are on the same power circuit as the fire alarm system, and something shorts out on that other device, the breaker that powers the shorted device and the fire alarm system will also shut off. Not a good thing.
Accidental Manual Power Shutoff
- When the entry heating system, a lighting system, or wall outlets are being serviced, power is turned off. If the fire alarm system is also powered by the same circuit breaker, then at the same time the other system is being turned off, the fire alarm system will be turned off. Sometimes the service work will be done in half an hour, like on the lighting system; sometimes it's not service work, it's actually turning off the other equipment for a whole summer season, like for the building entry heater. This is not a good thing, either.
Yes. When the power to the fire alarm system is turned off, the trouble light and buzzer turn on, calling attention to a trouble on the fire alarm system. Not only that, but there's a backup battery that keeps providing power to the system for at least 24 hours.
The problem is that there are a number of times that I've gotten to a site where I hear the words "I can't reset the trouble, and the buzzer in the panel keeps sounding off every day." In other words, the fire alarm system is sometimes in trouble for several days before the building management or owner calls for service.
The backup battery can't keep the fire alarm system running that long.
Reducing Failure of the Fire Alarm System
To reduce the chances that a GFCI breaker or a AFCI breaker shuts off the power to the fire alarm system, the Code prohibits GFCI or AFCI breakers for the fire alarm system. To reduce the chances of an automatic power shut off from a shorted device, or a person inadvertently shutting off power to the fire alarm system, the Code prohibits any other load on the branch circuit.