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Section 4: Slc Circuits With Isolators; Fault Isolator Devices; 1: Isolating An Slc Branch - Honeywell SLC Installation Manual

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Section 4: SLC Circuits with Isolators

4.1 Fault Isolator Devices

There are three isolator devices used to protect critical elements of the SLC from faults on other
SLC branches or segments.
Fault Isolator Module I300
Six Fault Isolator Module ISO-6
Isolator Detector Base B224BI
A Fault Isolator Module on both sides of a device, or the combination of Isolator Base and Isolator
Module is required to comply with NFPA Style 7 requirements.
• If relay or sounder bases are not used, a maximum of 25 addressable devices can be
connected between Isolator Modules and/or Bases. When relay or sounder bases are used,
the maximum number of addressable devices that can be connected between Isolators is
reduced to seven. Isolator modules will not function properly when these limits are exceeded.
When more than 100 Isolator Modules are connected to an SLC loop, the address capacity
of the loop is reduced by two (2) addresses for every isolator device in excess of 100.
4.1.1 Isolating an SLC Branch
The module continuously monitors the circuit connected to terminals 3(–) and 4(+). Upon power-
up, an integral relay is latched on. The module periodically pulses the coil of this relay. A short cir-
cuit on the SLC resets the relay. The module detects the short and disconnects the faulted SLC
branch or segment by opening the positive side of the SLC (terminal 4). This isolates the faulty
branch from the remainder of the loop preventing a communication problem with all other address-
able devices on the remaining branches (labeled "Continuation of the SLC" in the figure below).
During a fault condition, the control panel registers a trouble condition for each addressable device
which is isolated on the SLC segment or branch. Once the fault is removed, the module automati-
cally reapplies power to the SLC branch or segment.
FireLite SLC Wiring Manual — P/N 51309:P4 9/17/2014

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