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...
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What Causes an Open NAC? -- I am going to a job site where on the service call ticket states that a NAC is reading open circuit. What can cause an open circuit on the NAC line?
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What is the Trigger Voltage for a Booster Power Supply? -- Most fire alarm control panels can provide a limited amount of power for the horns and strobes, but extra power for the horns and strobes can be provided by a Booster Power Supply -BPS-. The term -Trigger Voltage- for the BPS is a shorthand term for -Whatever voltage is necessary to turn on the Booster Power Supply-. Depending on...
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Are Breaker Locks Required if There's No Control Panel? -- A Fire Detection and Alarm System is a system that detects fire and warns people of danger. As such, it should never be turned off; it's a life-safety system. If it's 120-volt detectors and pull stations connected to relays that sound bells throughout a building, it's still a life-safety fire alarm system. If it ever was turned off, people occupying a building would not be warned of a fire...
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How do I Address the Pull Stations? -- The numbers that you dial into the devices are address numbers. They're shortcut addresses. Instead of saying -Pull Station, 2nd Floor, North Stair- you dial in the 2 digit number. It's much easier for the electronics to use a 2 digit number instead of the long description; the short number takes a lot less time to send than the long description...
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How are the Horns and Strobes Activated? -- A fire alarm system is a Detect Fire and Warm People about the Fire system. It has automatic detection devices like smoke detectors, heat detectors, and waterflow switches -- it has manually operated input devices like pull stations and MCPs -Manual Call Points-. The detection devices send their alarms to a Fire Alarm Control Panel or FACP. Automatically deciding what to do when there are alarms, the control the control panel has circuitry to sound the alarm. Providing electrical power to...
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Are Addressable Fire Alarm Systems Different from Conventional Systems? -- Many fire alarm people think that an addressable fire alarm system is totally different from a conventional fire alarm system. But is it? A NAC circuit -Notification Appliance Circuit-, for instance, is a totally conventional circuit. Any addressable panel that has a NAC circuit has a conventional NAC circuit. If there are..
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What is Voltage Free Interfacing? -- The terms -Potential Free- or -Voltage Free- are engineering terms for -The module has relay contact outputs only-, and it doesn't provide power for anything, or supervise anything -- it doesn't check continuity of any wires. It also doesn't provide power or voltage to activate anything...
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What Happens to the SLC when a Device is Disconnected? -- A Signaling Line Circuit (SLC) has two purposes: (1. An SLC is used to send signals between the control panel and the devices on the loop (2. An SLC is used to provide power from the control panel to the devices on the loop. To understand what is going on electrically...
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What do We Include in Battery Calculations? -- When deciding what to include in the battery calculations, we look at the reasons for making these calculations in the first place. A fire alarm system is a life safety system; if the system doesn't work, people can get hurt - or worse. The times that the fire alarm system is supposed to work are -Always-, including the time during a power outage...
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What is the Difference Between Class A and Class B NAC Circuits? -- The short explanation is that coming into the panel for Class A, there are a total of 4 wires, and for Class B, there are a total of 2 wires. However, to understand that short explanation, one needs to know the difference between Class B and Class A from a life-safety point of view. Electricity has to get to the horns and strobes in order for the horns and strobes to warn people of a fire. For electricity to flow, however, the electrons require a complete electrical path. Electrons cannot flow through a wire, unless there is somewhere to go...
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Can the Fire Alarm Zones be for Multiple Floors? -- A zone on a fire alarm panel display is shown either with labeled lights -like "Basement", "1st Floor", "2nd Floor", "3rd Floor", Etc.- or with words on a graphic display. -- A zone is where you are going to send the fire department when there's a fire -- A zone is where you are going to send the building owners when there's a false alarm -- A zone is where you are going to send the fire alarm technician when the system needs fixing -- If the fire alarm system is an addressable system that uses words on the display, all the devices are shown as separate devices, each device is actually ...
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What is the Maximum Number of Zones Permitted? -- The NFPA (National Fire Protection Association) doesn't decide how many inputs or outputs can be on a fire alarm panel, and they don't decide how many zones we can attach to a fire alarm control panel. These decisions are left up to the manufacturer of the panel. The NFPA, however, does indirectly control how well the panel is going to work. Once the panel is designed and ready, the manufacturer has to get the panel tested by a...
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How is the Standby Power Calculated? -- In case there's a power outage, the fire alarm system still has to detect fire and warn people of fire. It would be nice if the fire alarm system could do this for days, weeks, or even years, until eventually the power can be restored, but the NFPA (National Fire Protection Association) is reasonable. In most cases, the NFPA is happy if the system can continue to work without power for 24 hours. This is the standby period. If there is a fire detected at the end of that 24 hours, the system still has to sound the alarm. Usually sounding the alarm takes up a much higher level of current than when the alarm system is standing by, so sounding the alarm has to be calculated separately. This is...
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What Is the Difference Between Conventional and Addressable? -- The word conventional doesn't mean Old and Obsolete, the word conventional means Sanctioned by General Custom. The conventional fire alarm system is the standard way, or ordinary way of making a fire alarm system. The Addressable portion of a fire alarm system isn't a replacement for a conventional fire alarm system, the Addressable portion is ...
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How is a Pathway Classified? -- The classification for a pathway is not determined by the method of carrying a signal or the type of signal the pathway is carrying - The classification is determined by what the pathway isn't or can't do - the classification is a process of elimination...
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What is Class N Power Over Internet (PoE)? -- Powering detectors and modules, Class N communication paths using Power over Ethernet (PoE) is coming to a fire alarm system near you. Probably not all of the systems or devices will use Class N PoE paths, but enough...
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Is an EOL Resistor Needed for an Addressable System? -- Normally, as I know, an addressable fire alarm circuit is without end of line resistor and conventional fire alarm circuit has an end of line resistor... But I found some documents online showing the FAS (Fire Alarm System) to work using an end of line resistor to measure electrical current and resistor. So how does an addressable system work?
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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...
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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...
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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...
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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 ...
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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...
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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 ...
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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 ...
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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 ...
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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...
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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 ...
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