Standard Digital (PHSC)

Standard Digital (PHSC)

The Standard Digital Protectowire Heat Sensitive Cable (PHSC) Linear Heat Detector can best be described as a continuous run of spot heat detectors. It is capable of sensing heat anywhere along its length and initiates an alarm once its fixed activation temperature is reached.

The Standard Digital (PHSC) Linear Heat Detector works in the following manner. Once the ambient temperature meets or exceeds its fixed temperature, the heat sensitive polymer weakens, which in turn allows the twisted spring steel conductors to make contact, which results in an electrical short that triggers an alarm signal.

The Standard Digital (PHSC) Linear Heat Detector is designed to be used on a compatible fire alarm control module or panel.

All Protectowire Linear Heat Detectors must be installed in accordance with applicable sections of NFPA 72 or as required by the local AHJ.


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    Unique advantages of Protectowire Linear Heat Detectors include:

    • Detects heat at any point along its length
    • Low maintenance
    • Outer jackets resist corrosion, chemicals, moisture, and extreme temperatures
    • Can be installed close to hazards to provide rapid response
    • Long service life


    * Proper handling and storage is mandatory to ensure detector performance. Exposure to heat above its fixed temperature rating will render the linear heat detector unusable and may not be obvious by its visual appearance.

    What is the primary difference between Protectowire PHSC and PLR Digital Linear Heat Detectors?
    Protectowire PHSC series is manufactured using spring steel conductors, while the PLR series is manufactured with low resistance tri-metallic conductors that are engineered to enable longer detector zone lengths on other manufacturers' control equipment. The amount of Protectowire (PHSC or PLR series) that can be installed on another manufacturers' control equipment is directly determined by the maximum loop resistance of the equipment’s initiating device circuit. Protectowire’s PHSC digital linear heat detectors have an approximate resistance of 0.185 Ohms per foot (0.607 Ohm per Meter). Protectowire’s PLR digital linear heat detectors have an approximate resistance of 0.058 Ohms per foot (0.191 Ohm per Meter). The PLR series detectors allow for approximately 3x longer lengths on the same initiating device circuit.
    Can Protectowire Linear Heat Detectors with different alarm temperature ratings be installed in the same zone?
    Yes. Protectowire offers two series of detectors capable of supporting different activation temperatures on the same series initiating device circuit. This allows a single Protectowire Linear Heat Detector zone to protect multiple areas with different ambient temperatures. The PHSC Series can support 135°F, 155°F, 190°F, 220°F, 280°F and 356°F being spliced into the same initiating device circuit. The PLR Series can support 155°F and 190°F being spliced into the same initiating device circuit.
    Is the alarm operating criteria in Protectowire PFS Series Fiber Optic Linear Detectors the same as standard digital type Protectowire Linear Heat Detectors?
    Unlike standard Protectowire Linear Heat Detectors, which operate on a fixed temperature alarm principle, the PFS Series Fiber Optic Detectors are user programmable by zone to operate on any one of the following alarm criteria:
    • Maximum temperature per zone
    • Temperature difference between a measurement location and the zone average (zone differential)
    • Temperature development per zone in terms of time (time differential/rate-of-rise)
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