Douglas Krantz - Technical Writer - Describing How It Works
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Can the Fire Alarm Control Panel Trip a Remote NAC Panel?

Can the Fire Alarm Control Panel Trip a Remote NAC Panel?


Can the Fire Alarm Control Panel Trip a Remote NAC Panel?


Greetings Douglas,

I want to pose two FA related questions for your review and response; assume this work would be performed in the USA under NFPA and IFC ruled jurisdictions.

Item #1: Many projects we work on have multiple NAC Extender Panels that service NAC circuits in either large common areas or in separate enclosed rooms. The questions relates to the code required means to trip all of the NAC Extender Panels in an alarm situation. What are the code rules for the following:
  • Trip using a separate NAC Circuit from the FACP?
  • Trip using a loop in a NAC circuit fed from the FACP which has other NAC appliances connected to it?
  • Trip using a an addressable control module on a SLC loop?

Item #2: Regarding sprinkler bell circuits, we typically feed the inside and outside bells using a 120V circuit fed through the water flow switch. Does this 120V circuit need to be a dedicated circuit?

Thank you, TM

The following responses are based on supervision, which is a fire alarm system's way of finding out that something's wrong so it will be fixed before a fire occurs.

Trip using a separate NAC Circuit from the FACP?

The panel's output to the NAC Circuit (Notification Appliance Circuit) has two conditions.

When the panel is not in alarm, the panel is supervising the wiring in the circuit by checking the continuity of the Conventional Class A or Class B wires. A small current is run through one of the wires, the end of line resistor, and back through the other wire. If the current stops because the wire breaks or comes loose, the panel's trouble light and buzzer are turned on.

When the panel is in alarm, it is providing 24 Volts Nominal power to the wiring.

Check with the installation manuals that come with the control panel and the expander panel to make sure they are compatible and that they are wired correctly.

Trip using a loop in a NAC circuit fed from the FACP which has other NAC appliances connected to it?

This is a two-layer issue.

One is the legal issue addressed in the installation book provided by the manufacturer of the NAC expander panel. If the installation books for both panels show that the NAC expander panel can be installed that way, and that they can be used with each other, then it is legal.

The other issue is a long-term service and remodeling issue.

The problem is that the people servicing and remodeling the system 5 to 10 years down the road are often not the same people that installed the NAC expander panel. You may have good as-builts, but more often than not, the as-builts are not available to anyone servicing the building's fire alarm system.

I've had to find and fix problems with a building's wiring. Have you ever spent a few hours to locate a NAC expander panel you didn't even know existed, only to find out that the batteries were 8 years old and the panel now considers the batteries bad? Wouldn't it have been nice to have the panel say, in words, that the NAC expander in the Basement North West Hall Ceiling is having trouble? If the panel said that, finding the problem would have been so much easier. Installing the panel that way, though, requires the panel to be on a dedicated NAC circuit.

When remodeling a building, often the fire alarm system has to be remodeled. Ten years down the road, it would be good to have the original fire alarm installing company doing the remodeling, and the person on site should have 10 years of experience. Doesn't happen that often.

When the person working on the fire alarm system doesn't recognize the panel and how it is wired into the system, the panel can be disconnected or mis-wired. With a disconnected panel, the disconnection might not be caught until the system is fully tested. Mis-wiring is worse. I have even seen the mis-wiring of a panel so that if the batteries in one NAC expander panel go bad, half the school building won't hear a fire alarm.

Using properly labeled dedicated NAC circuits, without any extraneous horns or strobes, helps a lot with long-term servicing and remodeling.

Trip using an addressable control module on a SLC loop?

The USB port on a computer is very similar to a Signaling Line Circuit. Modules, both input and output, are part of the control panel's signaling, control, and power system.

USB stands for "Universal Serial Bus" and provides for two-way communication between the computer and peripheral devices like keyboards, monitors, external memories, etc. It also provides power to operate many of these devices.

SLC stands for "Signaling Line Circuit" and provides for two-way communication between the computer (Fire Alarm Control Panel) and peripheral devices like addressable input modules, addressable detectors (which are detectors with internally attached input modules), addressable non-supervised control output modules, addressable supervised output modules, etc. The SLC also provides power to operate these modules.

There are some differences between a USB (Universal Serial Bus) and a SLC (Signaling Line Circuit), but the basic concept between the two is the same. They both provide two-way communication and power from the control box to the end devices.

In essence, the fire panel is able to communicate both directions with every module. If the communication stops between the panel and any module, the panel says there's trouble with that module. That's supervision.

Addressable Non-supervised Output Control Module

A Non-supervised Addressable Control Module on a Signaling Line Circuit (SLC) loop is another way of saying relay contacts. There is no direct supervision of anything connected to the relay contacts, there is no way of telling if the NAC Expander Panels (Notification Appliance Circuit) are connected to the system. Even with an Addressable Input Monitor Module to show if there are troubles on the NAC Expander Panels, the wiring from the relay contacts of the control module could come loose and no one would find out there's a problem until there is a fire. In that case, there wouldn't be an evacuation sounding for anyone in the are if there's a fire.

Non-supervised addressable control modules are not a good idea to use for tripping the expander panel without some other way of supervising the wiring.

Addressable Supervised Output Control Module

A Supervised Addressable Output Module on a SLC (Signaling Line Circuit) is another way of saying NAC (Notification Appliance Circuit) Output Module. Besides the terminals for the SLC, it has power input terminals and supervised output terminals.

A supervised output module supervises the Conventional Class A or Class B circuitry on its output exactly the same way as the control panel supervises the NAC Conventional Class A or Class B output. It does a continuity check of the wiring by running a small current through one of the wires, the end of line resistor, and back through the other wire. If the current stops because the wire breaks or comes loose, the panel's trouble light and buzzer are turned on.

The power applied to the power input terminals can be 24 Volts Nominal, Voice Evacuation Audio, Firefighter's Telephone, Etc. The module's output, just like the control panel's NAC output, switches between Supervising the wires when the panel is not in alarm, and providing the external power when the panel is in alarm.

Is It Legal?

All fire alarm systems have to be installed according to how the manufacturer has had the system tested and listed by a third party, nationally known, testing laboratory like UL, FM, ULC (Canada). CE (Europe), Etc.

In order for the manufacturer to get approval for the listing, one of the requirements is that everything provided by the manufacturer has to have accurate installation sheets showing the specifications of the equipment, and exactly how it is to be installed.

If method of installation or wiring is not on the specifications provided by the manufacturer, talk to technical support for the manufacturer. There might be some exceptions that you need to be aware of.

In other words, in order to find out whether or not a control panel, NAC expander power supply, or a module can be used legally, check with the instruction sheets that come with the equipment. That's one of the reasons the installation sheets are there.

Be careful about what you read, though. The sales literature on the web is sales literature and has not gone through the testing and listing process. Read the installation sheets.

If the addressable output control module or NAC expander power supply is installed according to the installation sheets, the equipment is installed correctly.

Outside Bell Circuit Power

The waterflow switch / outside bell is a complete detect and warn fire alarm system, except that it is not supervised in any way.

If a wire breaks, no one will find out until the next time the bell circuit is tested. If a fire breaks out after the wire breaks but before the circuit is tested, it won't work.

On a non-dedicated breaker, if the power is turned off to something else on the circuit breaker for servicing, the bell won't work. Worse yet, if the power is turned off long term to something else on the circuit breaker, no one will find out until the next time the outside bell is tested, or a fire occurs, whichever comes first.

It's probably in the NFPA Code somewhere that the circuit for the waterflow switch / outside horn has to be on a dedicated circuit. But the NFPA Code is based on common sense, and common sense says "This is for life safety, make sure it is reliable". If the circuit is dedicated, there is a lot less chance the circuit will be accidently turned off and left off. Make it a dedicated circuit.

When installing a dedicated circuit breaker, install some sort of lock-on device on the breaker so it won't accidently be turned off. Make sure there's no arc-fault tripping of the breaker and no ground fault circuit interruption device in the system to reduce the possibility of something automatically shutting off power. Use a red breaker as a visible reminder to not mess with the system.

Douglas Krantz

facpdoug@douglaskrantz.com
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