Douglas Krantz - Technical Writer - Describing How It Works

Can You Put Initiating Devices on a NAC Panel?

The NAC Panel, or NAC Power Supply, only provides power to the Notification Appliances like Horn, Strobes, Speakers, etc. The Notification Appliances don't detect fires, but warn (or Notify) people of fires.

A NAC Panel or NAC Power Supply provides power to the Notification Appliance Circuit in the building.

Greetings Douglas,

Do you usually put initiating devices on a NAC Panel? Or is it notification devices only?

Thank you, JD

The easy answer would be to say no, you can only use the notification devices on the NAC Panel. But you deserve a more complete answer.

The NAC Panel is a Power Supply

The letters "NAC" don't stand for the panel-on-the-wall, the letters "NAC" actually stand for the electrical circuit that's outside of the panel. The Notification Appliance Circuit (NAC) is the electrical "Circuit" that carries power to the Notification Appliances like horns and strobes.

For the fire alarm auxiliary panel, most manufacturers use a model name like "Booster Power Supply (BPS)", "Signal Power Expander (SPX)", "NAC Power Booster", or some other descriptive model name for the "NAC" box-on-the-wall. Even though the power supply is often referred to as a NAC Panel, it's really a fire alarm rated power supply for the Notification Appliance Circuits.

In essence, when there's a fire alarm, this "NAC Panel" provides power for the horns so they make noise and power to the strobes so they will flash.

Because often, the Fire Alarm Control Panel (FACP) just does not have enough power to run all of the horns and strobes, the auxiliary power supply is often used to provide the needed extra power. This auxiliary panel is also used so the wires between the power supply and the horns and strobes can be kept short.

Most of the time, the power supply does not provide power to the horns and strobes. It's only when the fire alarm control panel "turns on the auxiliary panel's power" (sends an alarm signal) that the "NAC Panel" provides the power on the NAC circuits coming out of the panel.

The NAC Panel is Also a Continuity Checker

Most the time, whenever the power supply isn't in alarm and powering the horns and strobes, the Notification Appliance Circuit Power Supply is checking (monitoring) the wires that are used to carry the power for the horns and strobes. It supervises the wires.

The problem is that the panel is too dumb to actually check to see if the horns and strobes themselves work. However, to make sure all of the horns and strobes are connected, the panel can run a continuity check of the wires.

As long as there is a complete electrical path conducting electricity from the panel, out to the end of line resistor, and back to the panel, the panel considers that all the devices are connected.

This is the wire supervision voltage/current that is normally measured on the circuit.

Connecting Devices

The alarm initiating devices (the devices like smoke detectors and pull stations that detect fire and send an alarm signal to the panel) cannot be powered by the NAC power supply; initiating devices can only be connected to the control panel using the IDC (Initiating Device Circuit) or using the SLC (Signaling Line Circuit).

The horns and strobes have to receive their power from the NAC circuit power output from the Fire Alarm Control Panel (FACP) or from an auxiliary NAC Booster Power Supply. A few addressable type horns and strobes can receive their control signals from the FACP through the SLC, but the power itself still has to come from an auxiliary circuit power output from the FACP or from a fire rated auxiliary power supply.

Douglas Krantz
Life Safety
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