How Protectowire Linear Heat Detection works
To understand how Protectowire Linear Heat Detector works, it is important to understand the basic construction of the detector.
1. Outer Jacket
Protectowire Linear Heat Detector is available with various outer jackets suitable for different environmental conditions. The outer jacket determines the detectors environmental characteristics. It is important that a suitable jacket type be selected for the environment which the detector will be subjected to. 
2. Mylar Wrap
Beneath the outer jacket is a Mylar™ wrap which provides additional protection for the inner conductors of the detector. 
3. Heat Sensitive Polymer
A Heat sensitive polymer coats the inner conductors of the Protectowire Linear Heat Detector insulating them from each other. The polymer is designed to be physically stable up to the rated alarm set point temperature of the detector. If the rated alarm temperature is reached or exceeded at any point along the detector, the polymer at that point becomes soft. This softening allows the inner conductors to contact each other producing an alarm condition (short) on the initiating circuit. 
4. Steel Twisted Pair
A twisted pair of steel conductors comprises the core of Protectowire Linear Heat Detector. The twist provides evenly distributed tension between the conductors which assures the detector actuates once it's alarm temperature is reached. The nature of a twisted pair also adds a measure of protection from induced electrical interference such as EMI and RFI which could effect monitoring circuitry. Steel conductors are used not only to make a durable detector, but for their unique electrical characteristics, which allow for Alarm Point Location. 
Monitoring of Protectowire Linear Heat Detector utilizes conventional initiating circuits
1. Supervision
The entire length of Protectowire Linear Heat Detector is supervised by a conventional initiating device circuit. A small current is continuously passed through the detector and end of line resistor (ELR). The end line resistor limits the amount of current to a preset level which the monitoring circuit is configured to treat as a normal condition.
 |
FROM CONTROL PANEL |
2. Fault conditions
If an open circuit condition occurs anywhere in the loop, current is no longer allowed to flow through the Protectowire Linear Heat Detector. The monitoring circuit is configured to treat this as a fault or trouble condition.
 |
FROM CONTROL PANEL |
3. Alarm Conditions
If a portion of the Protectowire Linear Heat Detector is exposed to heat above it's rated alarm temperature the heat sensitive polymer breaks down and a short occurs at that point. This bypasses the end line resistor greatly increasing the current flow through the loop. The monitoring circuit is configured to treat this as an alarm condition.
 |
FROM CONTROL PANEL |
3. Alarm Point Location - Protectowire FireSystems Control Panel Exclusive
If the Protectowire FireSystem control equipment is configured with the Alarm Point Location Option, a linear distance representing the length of Protectowire Linear Heat Detector from the start of the Protectowire portion of the circuit to the actuated point can be displayed at the control panel.
 |
ALARM POINT LOCATION AT PROTECTOWIRE PANEL |