Learn These Common Fire Alarm Codes (Part 2)

By Andrew Erickson

July 8, 2023

The response from my previous article on common fire alarm trouble code definitions has been tremendous. It's been among the most popular articles I've written, and I've actually heard from many of you who have called us (1-800-523-7232), emailed (info@digitize-inc.com), or used the website chat box.

In many cases, I'm sure you'll just get a fast definition from this page and leave happy. In other cases, if you're working on a broader fire alarm project, I hope you'll stick around and use the growing collection of articles here to make your job easier.

Now, to continue our discussion on alarm codes, let's take a look at some others that you may run into. Here's the list:

"Wireless Device Supervision Fault"

The "Wireless Device Supervision Fault" trouble code indicates that the fire alarm control panel is unable to communicate with a wireless device in the system. This can occur if the device has been moved too far from the control panel, if its battery is dead, or if there is interference with the wireless signal.

How do you resolve this? Ensure that wireless devices are within range and powered properly to avoid or clear this trouble code.

This code is obviously not a factor in traditional wired systems, but that's not to say that you should avoid wireless systems. In many ways, they offer superior performance. There are plenty of wire-specific alarms that you're trading away as you gain this additional trouble code.

"Ambient Temp Too High"

The "Ambient Temp Too High" trouble code indicates that the temperature in the vicinity of the fire alarm or a specific sensor is higher than the safe operating range. This could potentially interfere with the device's operation and cause false alarms.

Conditions leading to high ambient temperature should be rectified promptly, especially because fire alarm equipment is generally quite rugged. If it is compelled to report that ambient temperatures are interfering with its operation, imagine what is happening in the building itself. If you don't yet have a fire on your hands, you might be well on your way.

"End of Line Resistor Fault"

The "End of Line Resistor Fault" trouble code indicates a problem with the resistor placed at the end of the line in a fire alarm system. This resistor's purpose is to monitor the line's integrity, and a fault could indicate a wiring issue. The resistor may need replacement, or there could be a break in the wiring that needs to be repaired.

This method of using a resistor is a rather ingenious way of getting 3 states from just one wire. In other remote contexts outside of fire alarms, it's common to use "normally closed (NC)" alarm contacts to self-monitor for wire faults. Unfortunately, these has the effect of making wire faults look exactly like alarms. This works fine for system maintenance alerts, but the cost of a false fire alarm is far too high.

If you see the "EOL" acronym on any fire panel, it's referring to these "End Of Line" resistors.

"NAC Fault"

The "NAC Fault" trouble code stands for "Notification Appliance Circuit Fault". It indicates a problem with the circuit that controls the notification appliances, such as horns, strobes, and bells. This trouble code could mean there's a wiring issue, a short circuit, or a problem with a notification appliance itself.

Although receiving alarms at your central station or proprietary alarm monitoring system is perhaps the most important aspect of fire safety, there's obvious value in the immediate public address provided via notification appliances.

If you have them installed in the first place, it's likely that they're required by NFPA fire codes anyway.

"Pull Station Trouble"

The "Pull Station Trouble" trouble code indicates a problem with one or more of the manual pull stations in the fire alarm system. This could be due to a wiring problem, a faulty pull station, or an accidental or malicious activation of the pull station.

Unlike many other aspects of fire alarm systems, pull stations are required to be placed within reach of building occupants or the general public. That greatly increases the possible mayhem they might encounter.

The affected pull station should be investigated and repaired or replaced as necessary.

"System Reset Required"

The "System Reset Required" trouble code is displayed when the fire alarm system has been triggered and needs to be manually reset. This usually happens after a fire alarm has been confirmed as false or once an actual fire situation has been resolved.

This is similar in concept to what you see after deactivating a burglar alarm. You'll often have to perform an additional acknowledgement step before the system can be re-armed.

All of these functions serve to ensure that no alarm state, however brief, goes unnoticed by the system administrators.

"Sensor Dirty"

The "Sensor Dirty" trouble code indicates that a smoke or heat sensor in the system is dirty and may not be functioning properly. Regular maintenance and cleaning of sensors are essential to avoid this trouble code.

A "sensor dirty" alert is a warning that, at some level, your redundancy has been reduced. This might not currently be a critical loss of functionality, but the coverage provided by your initiating devices does have one small hole in it.

"Silence Switch Active"

The "Silence Switch Active" trouble code is displayed when the silence switch on the fire alarm panel has been activated, muting the fire alarm system's sounders. This is often used during maintenance or testing. However, if this code is displayed unexpectedly, it should be investigated immediately.

There's nothing worse that leaving a system in "test mode" accidentally. In some aviation-equipment monitoring projects I've worked on in the past, the mantra is always: "Better to provide no information than false information."

I'm reminded of that past experience as I think about silence switch activation. This is especially true in this fire-alarm context, when silence during an active fire alarm situation is inherently false information.

"Voice Evacuation Trouble"

The "Voice Evacuation Trouble" trouble code indicates a problem with the system used for voice evacuation announcements. This could be due to a problem with the speaker system, a fault with the audio source, or a problem with the control module.

This is quite similar to the NAC fault, although it's about the alerting device itself rather than the communication circuit.

"Fire Drill Mode Active"

The "Fire Drill Mode Active" trouble code is displayed when the fire alarm system is in fire drill mode. This mode is used during fire drills to simulate a real fire scenario without actually triggering a full-scale alarm. This code should only appear when the system is intentionally placed in this mode. If it appears unexpectedly, it should be investigated.

Imagine the chaos and threat to life safety if your system treated a real-life fire emergency as a simple fire drill.

Find Your Local Distributor/Installer (or Become One!)

At Digitize, we're a manufacturer of fire alarm monitoring systems. We can and will help you directly, and you can also get region-specific help from a local distributor/installer. Just give us a call and we'll connect you with a distributor in your region.

You can also become a Digitize distributor. Call us to talk about that, also.

Call us at 1-800-523-7232 or email info@digitize-inc.com

UPDATE: Get Even More Alarm Codes

I have written additional articles after noticing the popularity of this page:

Andrew Erickson

Andrew Erickson

Andrew Erickson is an Application Engineer at DPS Telecom, a manufacturer of semi-custom remote alarm monitoring systems based in Fresno, California. Andrew brings more than 17 years of experience building site monitoring solutions, developing intuitive user interfaces and documentation, and...Read More