28
Johnson Controls, Inc. SLC Wiring Manual —
P/N 51870:G 04/23/2009
Section 5: SLC Circuits with Isolators
5.1 Overview
There are two isolator devices used to protect critical elements of the FlashScan-mode or CLIP-
mode SLC loop from faults on other SLC branches or segments.
•
Fault Isolator Module
M500XJ
•
Isolator Detector Base
B224BI
A Fault Isolator Module on both sides of a device, or the combination of an Isolator Base and
Isolator Module are required to comply with NFPA Style 7 requirements.
5.2 Fault Isolator Module
The M500XJ module continuously monitors the circuit connected to terminals 3(–) and 4(+). Upon
powerup, an integral relay is latched on. The module periodically pulses the coil of this relay. A
short circuit 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
faulted branch from the remainder of the loop preventing a communication problem with all other
addressable devices on the remaining branches (labeled “Continuation of the SLC” in the figure
belowFigure 5.1). 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 automatically reapplies power to the SLC branch or segment.
5.2.1 Wiring an Isolator Module
Figure 5.1 shows a Style 4 example for wiring of an Isolator Module.
!
CAUTION:
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. IFC-300 or IFC-400 The
address capacity of the loop is reduced by two (2) addresses for every isolator device in excess of
200 when the Isolator Modules and/or Isolator Bases are connected to the SLC loop from the IFC-
320/E/C, IFC2-640/E, IFC-640/E, IFC2-3030, IFC-3030, or IFC-200.
SLC
Isolated branch
of the SLC
S
L
C-iso
wire
.cdr
Continuation
of the SLC
OUT
OUT
IN
IN
Figure 5.1 Wiring the M500XJ Module