Increasing Your Fire Alarm Literacy
FIRE PROTECTION
Part three in a series that examines a vital link in the fire protection system.
The fire alarm panel (FACP) acts as the control center, or brain, for the entire fire alarm system. A fire alarm annunciation panel (FAAP) is an FACP that contains principally readout indicators or lights.
Older FACPs use relays to perform required functions. Today’s technology uses a combination of transistors, diodes, and relays—-called solid state technology. There are drawbacks to solid state technology and each must be carefully evaluated. For one, it has a tendency to fail when the power supply voltage fluctuates up or down, or when lightning strikes nearby. Many alarm system designers have not yet mastered techniques to protect electronic alarm equipment from these electrical system transients.
Fire alarm control panels contain important modules or circuits, indicator lights, and switches. Remember, initiating circuits send signals to the panel. Signaling circuits give notification to building occupants. Following are the more prominent features and controls.
Power supplies. An internal power supply takes the building voltage and transforms it into 24 VDC (volts direct current). This voltage is used to power control panel circuits, initiating circuits, and signaling circuits connected to the control panel. High voltages are neither desirable nor usually allowed on detector and signaling device circuits. The expected fire alarm circuit voltage is 24 VDC.
Fire alarm control panels have emergency power supplies in case the building’s electrical power fails. Batteries usually provide this backup power. Properly designed fire alarm systems contain 24 hours of systemmonitoring battery backup power to initiating devices. On the other hand, if a fire alarm trip occurs, the battery supply must supply power to signaling devices for at least five minutes. Therefore, keep in mind that initiating or signaling devices cannot be arbitrarily added to existing fire alarm systems without recalculating the capacity of the backup batteries.
Types of signals. The FACP generates three types of signals—alarm, supervision, and trouble—and the firefighter must be able to identify each. The differences are distinct and important. Prefire planning activity provides firefighters with an excellent opportunity to review panel operations in their first response district. While it takes considerable effort to obtain this knowledge, it is incumbent on the department to do so.
An alarm signal is the way the FACP tells the “world” that an emergency exists. Operation of a heat or smoke detector, water flow, activation of special protection systems, or any other initiating device causes an alarm signal. A red indicating light and audible signaling devices let the occupants and the firefighter know an alarm condition is in progress. If there is more than one initiating zone, a labeled red light identifies each tripped zone. The following events cause fire alarm indications:
- Activation of any common initiating device on any zone.
- Activation of an automatic sprin-
- kler system flow switch.
- Activation of a specialty fire extinguishing system such as halon, carbon dioxide, or dry chemical.
Supervisory signals indicate that a critical device in a suppression system is in a condition that might prevent the system from performing properly. This condition is referred to as system impairment, A common application of this monitoring condition is sprinkler system control valve supervision. For example, a switch on a post indicator valve (PIV) operates when the valve handle is turned. This alerts the FACP that the valve is being tampered with and that the suppression system may not work properly. In certain cases guard tour stations and lock-boxes at free protection system checkpoints are connected into supervisory signal circuitry.
Supervisory signals light an amber lamp and produce an audible signal on the control panel. Usually they are zoned, and more than one supervisory switch can be on a single zone. The building occupants are not alerted by the signaling devices in the case of a supervisory alarm. The following actions trigger supervisory signals:
- Unauthorized movement of an automatic sprinkler system control valve.
- Failure of a security guard to activate an inspection switch on his tour of inspection.
- Operation of valves, failure of air pumps, or other actions that may disable any type of fire protection system.
- Leaks in the system less than the calculated fire discharge.
Trouble signals indicate that critical FACP components or circuits have failed. The trouble signal is also an amber light and audible signal at the panel. The building evacuation alarm is not activated. Trouble signal circuitry watches over the integrity of initiating and signaling device wiring. If a wire in the initiating or signaling device circuit is cut or is shorted to ground, a trouble signal operates.
Damage to most supervisory circuit wiring does not trigger a trouble signal. However, after this year it is probable that supervisory signal circuits will be trouble-monitored. The following conditions typically cause a trouble indication:
- Removal of detectors from sockets.
- Initiating circuit, open or short.
- Signaling circuit, open or short.
- Building power supply failure.
- Blown fuse.
- Loose or disconnected battery leads.
- Failure of critical FACP components.
There is nothing a firefighter should or can do about any of these failures. System repair is the responsibility of the owner and a qualified service agency.
SWITCHES AND CONTROLS
Fire department personnel operate only a few switches and controls on an FACP. The ones that they do operate help them determine why the alarm occurred. Following are some examples of switches and controls.
Alarm silence switch. When an alarm condition occurs on any initiating device circuit, audible and visible signaling devices within the building operate. A red alarm light operates on the panel, and an alarm zone indicates. The alarm silence switch allows the control panel operator to continue receiving the alarm from the initiating device and continue displaying a visible signal, but it silences any audible signaling devices.
This switch is a potential life hazard in the hands of irresponsible people. Operation of this switch before arrival of the public fire department or even before calling the public fire department has resulted in disaster. For example, people died in hotel fires when unbelieving front desk personnel silenced alarms because they did not want to disturb guests.
When and how to operate the alarm silence switch is critical; who operates the switch is even more critical. It is imperative that the authority having jurisdiction set a policy designating the operational procedure for the alarm silence switch.
Understand that even though the fire department operates the alarm silence switch after the first initiating zone trips, if another zone trips the audible and visible signaling devices will again operate until the alarm silence switch is operated a second time. Firefighters must carefully observe and note which initiating zones are showing on their arrival. After they silence the signaling circuits, other zones may trip later, setting off the signaling circuits again. This can be a good indication that smoke, heat, or fire is spreading elsewhere throughout the structure. When entering an occupancy where fire alarm audible devices are sounding, it is acceptable to silence the signaling devices if occupants can be moved efficiently without them.
Fire alarm reset. Some manufacturers label this the system reset switch. When an initiating device activates, the fire alarm panel reacts by going into the signaling mode. Some initiating devices are able to reset themselves. Nevertheless, the FACP stays latched in the signaling mode because of the alarm. Avoid resetting the system until a thorough search has been made of the premises. If it appears that there is a defective initiating device somewhere in a zone, keep records of which zone keeps tripping, the time of day, and other circumstances involved. This information is critical and valuable to inspection and fire alarm service personnel when they attempt to solve unexplained device trip problems.
Trouble silence switch. This switch silences the alarm at or inside the FACP itself without affecting the trouble signal. It does not silence house signaling circuits. If house signaling circuits are sounding, an alarm, not a trouble, condition exists.
Fire department disconnect. This switch is also called the city connection disable switch. It is normally in the “on“ or “connect” position. It disconnects the fire alarm panel from the outside monitoring agency if one is connected. (Remember, all fire alarm panels are not connected to outside monitoring agencies.) Fire companies should not operate this switch unless authorized to do so by the authority having jurisdiction. Most panels produce a trouble signal when this switch is operated to “off’ or “disconnect.”
Battery test switch. This switch temporarily removes the panel from building voltage and connects it to the battery supply. It also may temporarily load the battery with a dummy, or simulated, load to determine whether or not the battery is in good condition. Exactly what this switch does is not important to fire departments as they do not operate it under ordinary conditions.
Indicator lamp-test switch. Modern fire alarm panels use light-emitting diodes (LEDs) for panel visual indicators. This device is closely related to the transistor and diode family. Older panels use incandescent light bulbs, which are similar to flashlight lamps. The LED technology is newer, provides longer life, and is more reliable than incandescent light.
The lamp-test switch connects voltage to all the lamps to make certain they can light. Since this switch is usually spring-loaded, it must be held in position to check the lamps. It automatically returns to the “off’ position.
PERSONNEL HAZARDS
The major hazard in an FACP is the 115-VAC, 60-Hz building supply voltage that powers it. In a well-designed FACP, all terminals with 115 VAC on them are protected. Nevertheless, avoid probing your fingers around inside the panel. It is safe for firefighters to operate panel switches. The normal operating voltage for initiating the signaling circuits is 24 VDC.
OPERATING THE FACP
When responding to an automatic fire alarm incident, the sequence of operations is as follows:
- Locate either the FACP or the FAAP. One should be in the normal path of fire department entry. Panel location should be covered in prefire planning.
- Observe the color of the indicating lamps. There should be at least one green lamp, which indicates the FACP is operating on the building power supply. The absence of a green lamp and presence of an amber lamp indicate the building power supply or FACP power supply has failed.
- Look for a red indicating lamp. If a red lamp and building audible/visible devices are operating, there is an alarm condition. The next question is, What device is tripped? In most cases the panel will not tell you.
When there is more than one zone in a fire alarm system, there is more than one red zone lamp. More than one lighted red lamp means an initiating device of some kind has tripped in each indicating zone. Observe which zones the lamps annunciate. Refer to paper documentation, a chart, or a map associated with the fire alarm system to discover which area of the structure the zones cover.
Zone documentation is another topic to be covered in prefire planning. Without proper documentation, the fire alarm zone indicators are meaningless.
The audible and visible signaling zone annunciators should be sounding on your arrival. If so, on orders of the incident commander you may silence them by operating the alarm silence switch.
4. Look for an amber indicator lamp if there is no red indicator. If there is an amber light, determine whether it is associated with a zone. The zone can be an initiating or signaling zone. There should be an audible alert at the panel.
The building signaling system should not be sounding. When the panel audible is sounding, if the firefighter operates the trouble silence switch it will not disturb the condition of the signal but only silence the FACP panel audible.
5. See if supervisory signals are causing amber lamps to light on the panel. On those panels that have a common trouble lamp, it may be difficult to determine whether the problem is an initiating or signaling circuit trouble, a panel electronics trouble, or a supervisory indication.
If the problem is not apparent, the incident commander can direct firefighters to check all sprinkler control valves. These are valves at the base of the riser, post indicator valves on the lawn, and any electrically supervised valve through which sprinkler water must flow in an emergency.
The only way a fire alarm control panel can communicate with fire service personnel is through audible devices and lights. The more sophisticated ones provide computer screens and printer readouts. Take adequate time to learn the types of signals and exactly what these signals mean. Only then can you decide what actions to take*
