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A resistor in a sensor circuit is used as a simple way to monitor the function of the circuit. The resistor has a calibrated and known voltage drop and current while the circuit is "normal". If there is a short-circuit, or an open-circuit, the voltage and current will change and trigger the trouble alarm.
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What is the main function of resistances in fire alarm circuit?
Heat changes the resistance of a circuit. The change is detected by the system, and activates the alarm.
Does a fire alarm circuit have to be in a separate conduit?
yes because of it having a signals, if it mix with power cable, fire alarm circuit get distributed.
What is a Fire alarm circuit style y?
Style Y is a designation of circuit performance under different states of the circuit. For example: an initiating circuit and a NAC circuit may both be class B, with a panel on one end of the circuit and a resistor on the other. If there is an open on either circuit (the panel doesn't see the EOL), then a trouble is initiated at the panel. However, if there is a short between the two wires on a circuit, the panel will react very differently on the initiating circuit than it will on the NAC. Style Y means that the fire alarm panel will display a trouble on either an open or a short on the NAC circuit, where style 4 means that the Initiating circuit will generate an alarm on the panel in the event of a short, and a trouble in the event of an open.
Why to use pnp transistor in fire alarm circuit?
You can use a PNP or an NPN transistor in a fire alarm circuit. Both will work. It all depends on how you want to energize the alarm, and with what polarity of signal.
Will manually turning off a shunt trip breaker set off the fire alarm?
Manually turning off a shunt trip breaker should not set off the fire alarm. The only way that the breaker could set off the fire alarm when turned to the off position is if there is an auxiliary contact on the breaker connected to the fire alarm circuit. This is not usually done because the breaker should be able to be turned off when doing maintenance on the breakers circuit. If the breaker is a mandatory feed breaker to a piece of fire alarm equipment and shouldn't be left in the off position it might have a trouble circuit connected to the fire alarm panel. A trouble alarm on a fire alarm panel is different from an alarm circuit alarm.
What is fire alarm style 4?
Stye 4 wiring for fire alarm systems uses a single wire "daisy-chained" between detectors and ending with a resistor.
Does a fire alarm control panel need a dedicated branch circuit?
Under the NFPA Fire Alarm Code, the control panel must have its own dedicated circuit, the circuit must be labeled "Fire Alarm Circuit" and the handle of the circuit breaker must be colored red. Other rules apply in jurisdictions that adopt other standards, or for other types of fire alarms. For example, under New Hampshire Fire Code, you are PROHIBITED from installing self-contained smoke alarms on a dedicated circuit.
What does nacs mean referencing fire alarm?
Notification Appliance Circuit
How is a circuit for a fire alarm marked in the panel?
In the US, NFPA 72 (2007) 4.4.1.4.2.2: "Circuit disconnecting means shall have a red marking, shall be accessible only to authorized personnel, and shall be identified as 'FIRE ALARM CIRCUIT'". Other codes, or earlier versions, may have slightly different requirements, such as marking it "FACP" for "fire alarm control panel."
What are the advantages and disadvantages of open circuit fire alarm system?
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A bimetallic strip can be used as a thermostst in a simple fire alarm system Explain in detail how a fire would cause the alarm to sound And describe how it could be activated at a lower temperature.?
a fire would bend the strip which would complete the circuit for an alarm. When cooled, it might complete another circuit, answering your second question.
How a fire alarm would be raised?
The fire alarm device is usually equipped with an Amercium-241 that is alpha emitter source together with a battery derived electric circuit. In the normal situation the alpha particles ionize the air causing circuit connection. However when there is a smoke the circuit is disconnected due to the smoke that acts as an insulator and hence the alarm is actuated.
