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Fire Alarm -- Description

Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer

Can Phone Lines, Fire Alarm Cables, and 120-240 Cables be Put Together? -- Besides the legal aspects, fire and safety issues, there's the interference problem. The voltages and currents from the 120-240 volt cables will be cross-talking to the low voltage cables. How much cross talk is produced will be affected by the actual currents in the high voltage cable, how tight they... Read More

What is a Four Wire Smoke Detector? -- A 4-wire smoke detector is just like a 2-wire smoke detector, except that it receives its power from an auxiliary power supply rather than the conventional Initiating Device Circuit. Both the 4-wire and the 2-wire smoke detector sense particles in the air and call the particles smoke... Read More

The Signaling Line Circuit (SLC) is a Data-Power Bus -- The SLC isn't an RS232 communication circuit. The SLC isn't an RS485 communication circuit. Proprietary to each manufacturer, the SLC is its own type of communication-line/power-supply circuit.... Read More

NFPA's 7 Classes of Fire Alarm Paths -- The NFPA has divided the signal paths in a fire alarm system into 7 classifications: Class A, Class B, Class C, Class D, Class E, Class N, Class X. These classifications don't show how to wire up anything, these classifications show what happens when things go wrong... Read More

Is it OK to Disconnect the Ground Fault Circuitry? -- I was researching a ground fault issue my client is having with his plant fire alarm system and a VFD installed in the plant. Would you happen to have any experience with this sort of failure or could you recommend ... Read More

Why is Supervised Wiring So Important? -- Based on Life Safety considerations, supervision makes the difference between building low voltage wiring and building fire alarm system wiring... Read More

Help - I have a City Circuit Trouble on My Panel -- I have a question about our Simplex 4005 fire panel. It is showing a "City Circuit Trouble 1". It's after hours and on the weekend ... Read More

You are right about keeping power and control wires separated -- Had a fire alarm system many years ago that had 24 volt smoke detector wires and 208 volt fan shut down wires in the same conduit: 250' run in the dirt under the bottom slab of a building. Read More

What are the basic parts generally available in any panel? -- I mean any brand. Let's say Simplex, Siemens, Edwards, Notifier, whatever it may be. There must be some default parts in all the panels. Can you please tell me what are and what the functions are? Read More

What are the Signals on the SLC? -- I would like to know what type of signal is there between addressable fire detectors and the fire alarm monitoring panel. Actually I want to know how the address / location of... Read More

What's the Difference Between Class A and Class B? -- The Fire Alarm System is a Life Safety System - so the occupants of a building can escape quickly, the idea behind a Fire Alarm System is that it will provide a warning that there is a fire. The trouble is, if something is wrong with the system, like a wire is broken somewhere in the building, the Fire Alarm System... Read More

Why Doesn't a Smoke Detector Always Detect? -- The NFPA wants smoke detectors tested in place to make sure smoke enters the smoke chamber. Keep in mind that a smoke detector can't detect smoke that doesn't get to the detector. When a smoke detector doesn't... Read More

Firefighter Don't Reset the False Alarm -- When the alarm sounds and the firefighter arrives, even for a false alarm, the firefighter is on site for property protection and life safety. So when leaving, from the point of view of the firefighter, the ... Read More

Can We Use Waterflow Switches for Liquid Suppression Systems? -- Can we use the Flow Switches and Pressure Switches that are used with water lines, for fire suppression system, if fire suppression system uses NOVEC 1230 liquid? Read More

Are All Smoke Detectors Polarity Sensitive? -- I have a question... Is it important for smoke detectors to be polarity correct? Are all smoke detectors polarity sensitive? Read More

Can the fire department make the owner bring the whole fire alarm system up to code? -- We failed the inspection with city due to lack of signage at pull stations in an existing apartment building. The signs are supposed to say LOCAL ALARM ONLY - IN CASE OF FIRE CALL 911 Read More

Can Fire Alarm Fiber be Run in the Same Conduit as BMS? -- Can fire fiber riser be run in the same riser conduit with BMS? We only have one riser conduit for both. The engineers are saying we need two separate conduits, your thoughts? Read More

Why reverse polarity for fire alarm horns? -- A fire horn is turned like a light; it turns on when power is applied and turns off when power is removed. But then again, to constantly check continuity of the wires (supervise the wires), the Fire Alarm Control Panel (FACP) always has power applied to the circuit. Read More

Can a Backup Generator be Used for a Fire System? -- For backup, does the signal power expander only use batteries as the power source or would a/c or a generator ever be used? Read More

Where Can We Get Parts for our Unsupported System? -- Our fire alarm systems are no longer supported by the manufacturers, can you suggest how we can get the parts we may need in the future?... Read More

Is the Fire Alarm Control Panel Necessary? -- Having detected a fire, a fire alarm system sounds the alarm. Other than the building wires that carry the signal from the fire detector to the fire horn, everything else in a fire alarm system ... Read More

What is a Fire Alarm Zone? -- Building zones aren't determined by where the wires are run for the fire alarm system, building zones are determined by the building's fire-control -- fire-fighting divisions and by the building's smoke-control divisions... Read More

How Does Multiplexing of the Signaling Line Circuit Work? -- Depending on what one needs to understand about a circuit, the circuit can be thought about in different ways. Take for instance a Signaling Line Circuit (SLC). A Signaling Line Circuit is a circuit that starts from the... Read More

What Makes the End of Line Resistor So Important? -- To allow the panel's internal ohmmeter to check the continuity of the wires (supervise the wires), the end-of-line resistor is at the end of the loop: the last device.Read More

What Is Fire Alarm Trouble Power? -- In the "Old School" type of fire alarm system, before the smoke detector was invented, even though the fire alarm systems used AC, all voltages were in a steady state: either on or off. Until someone ... Read More

Just What Is a Signaling Line Circuit (SLC)? -- The SLC (Signaling Line Circuit) is another way of saying Data and Power Circuit. Along with added power to run the sub-computers and their input and output circuits, it's a computer data-buss ... Read More

If It's There -- It Has To Work -- Whether its smoke detectors on the ceiling or the firefighter's telephone system, people think that if it's there, it's real and it works. Sometimes, people even stake their lives on that device or system ... Read More

What is a 4 Wire Smoke Detector? -- Even though it uses an internal protection resistor and internal alarm relay contacts, a 4 wire smoke detector is basically a 2 wire smoke detector; it detects smoke and sends an alarm ... Read More

Why Can't You Reset a Trouble on a Fire Alarm Panel? -- Often times, when going on a service call as a troubleshooter, the building manager or maintenance person says... Read More

Why Have Wire that Lasts 2 Hours in a Fire? -- The fire alarm system is used to tell people when it's their turn to evacuate a burning building. Evacuation sometimes takes time... Read More

What is a Fire Alarm System? -- Long ago, as earliest method of spreading the word of fire danger, people shouted "Fire!" Depending on the circumstances, people would run... Read More

What are those Lights and Buttons on the Fire Alarm System For? -- You're now in charge of the building, be it an apartment building, office building, business complex, or industrial complex and now you have to deal... Read More

What Should One Look For in a Fire Alarm Panel? -- The question has been asked, "Which is the best fire alarm panel?" A fire alarm system isn't: installed for the manufacturer or... Read More

What is Total, Staged, and Defend-in-Place Evacuation? -- For their own safety, when the fire alarm sounds, people want to get out of a burning building. Sometimes, though, there's a hitch ... Read More

What Makes a False Alarm so Dangerous? -- Each false fire alarm increases the severity of a real fire. The increased severity from false alarms comes from the greater chance of loss of life or a greater chance of injury. This is a progression - with no false... Read More

Why Have a Written Fire Evacuation Plan? -- One time, I had a fire inspector tell me that he requires a written evacuation plan for all buildings. The reason... Read More

How good are those Call 911 signs above pull stations? -- The Fire Marshal didn't have the authority to require the owner to upgrade the fire alarm system to use off-site monitoring. Because... Read More

I Can't Fix Fire Alarm Systems that are Reset -- Help! I service fire alarm systems. When I'm on call, I have to respond on a 24/7 basis to fix fire alarm systems . This includes those systems that... Read More

Can One Company Really Keep the Other Company In Line? -- I'd like to tell you a story about dishonesty. Not the kind where a vendor knows he is doing wrong, and... Read More

What is Mass Notification? -- When a disaster or emergency strikes, and everyone in the area is to take action now, a Mass Notification... Read More

What is an Area of Refuge? -- You hear the message "Use the Stairs, "you see the sign "In case of fire, don't take the elevator." To get out of the building from the higher floors, when the building is on fire, the stairs ... Read More

How is a Buffer Relay Wired Into a Door Holder Circuit? -- Like a door stop, a door holder keeps a fire door open. When smoke is detected, the door holder releases, allowing the door to shut. The door holder looks simple and innocuous enough... Read More

How Are Fire Alarm Loops Supervised to Make Sure They Continue to Work? -- Because the fire alarm system is a Life Safety System (people's lives depend on the fire alarm system working in an emergency), using supervision, the panel makes sure the field devices are always... Read More

Why Does the Fire Alarm Panel Supervise the Wires? -- Supervision of building wiring isn't really to make sure the wires are good, supervision of building wiring is to make sure all the devices are ... Read More

How Do You Troubleshoot Using Supervision Voltage? -- With Fire Alarm Systems , one method of troubleshooting is measuring supervision voltage . It's the voltage at the panel's IDC input terminals (Initiating Device Circuit for... Read More

How Does the Fire Panel Know Addressable Detectors are OK? -- It's assumed that fire alarm systems have to work all the time because fires happen anytime, but, then again, this is the real world. Problems with... Read More

What's the Difference Between Class A and Class B? -- The Fire Alarm System is a Life Safety System - so the occupants of a building can escape quickly, the idea... Read More

What is Fire Alarm Class B Wiring? -- Fire alarm people are paranoid. They're afraid everything is working against them. They're in fear that that if anything goes wrong... Read More

How Does Class A Fire Alarm Wiring Work?-- Fire alarm systems save lives and protect property. Fire alarm systems also break down because... Read More

How is an End of Line Resistor a Pull-Down Resistor? -- Sometimes when troubleshooting, the technician has to think inside the box. For instance, take... Read More

Why Use Class A to Network Fire Alarm Panels Together? -- In a tall building, should the network connecting the fire alarm panels together be Class B, or Class A? Read More

How Does Resistance Affect the Initiating Device Circuit (IDC)? -- IDC circuits (Initiating Device Circuits) are input circuits to the fire alarm control panel, and...Read More

What is a Booster Power Supply or Signal Power Expander? -- A fire alarm system consists of input devices to detect a fire (automatic detectors and manual pull stations), output devices to notify occupants of... Read More

What Is a Conventional Notification Appliance Circuit or NAC?-- NAC is the acronym for Notification Appliance Circuit. Notification: Tells people of a Fire or other Life... Read More

What is Notification Appliance Circuit (NAC) Supervision? -- In the Notification Appliance Circuit (NAC), conventional fire horns, bells, strobes, chimes, and speakers, all have the... Read More

What will a Shorted Fire Strobe Do? -- Some time ago, at a high rise business and condominium building, I inspected a fire alarm system. On arrival, the fire alarm control panel showed...Read More

Why is the Voltage on the Notification Appliance Circuit (NAC) so Weird? -- Normally, when the Notification Appliance Circuit (NAC) isn't in trouble, the NAC is in one of two states or conditions: Alarm (making noise and... Read More

Why does Fire Alarm Strobe Current Go Up as Voltage Goes Down? -- In a fire alarm system, strobes are notification appliances; the flashing strobes get people's attention. They're constant... Read More

What is a Fire Alarm Klaxon? -- Before there were DC fire horns, and as an alternative to clanging bells, klaxons were used to notify... Read More

Why Can't a 70 Volt Speaker be Used With a Fire Alarm System? -- When the fire alarm system is active and is being used for EVAC or voice, there is no difference between the speaker audio used... Read More

What is an RTU (Roof Top Unit)? -- "Help! I have an alarm on my fire alarm panel saying something about RTU, but it won't reset," so goes the cry... Read More

What is Smoke Power on a Fire Alarm Panel? -- 2 Wire Smoke Detectors are connected to the Zone Inputs of a conventional Fire Alarm Control Panel (FACP) , and so too are 4 Wire... Read More

Conventional Four Wire Air Duct Smoke Detectors -- Conventional Air Duct Smoke Detectors are assemblies that include a smoke detector, support electronics, and an internal power supply. The minimum requirements... Read More

What is Smoke Detector Verification?-- Because smoke comes in so many varieties, smoke detectors have to be sensitive... Read More

Should the Detector be Photo, Ion, or Both? -- In a smoke alarm, the smoke detector senses particles in the air from a fire and then the alarm sounds. Hearing the... Read More

Why do Fire Alarm Pull Stations Break? -- Ever wonder why a manual pull station tends to break when someone attempts to push it back after setting off the alarms ? I, too, have been wondering... Read More

Why Does a Smoke Detector Stop the Elevator? -- Back in the early '70s, the disaster movie "Towering Inferno" depicted a fire in a high rise office building. Trapping partygoers... Read More

What is a Firefighter's Telephone System? -- In a large building, so they can talk to each other while battling fires, firefighters use their two-way radios. But when the radios just don't work, the firefighter's... Read More

What is a Stair Pressurization Fan (SPF)? -- In case of fire in a high rise building, an SPF uses clean outside air to pressurize the air in stairwells. The pressurized air helps people escape... Read More

Is the NFPA Code the Law or a Recommendation? -- In the United States, the National Fire Prevention Association (NFPA) fire codes are strange. They aren't codes; they're... Read More

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