M500Xj Isolator Module - Johnson Controls AIM-200 Technical Manual

M500XJ Isolator
Module
24 Addressable Intelligent Module—AIM -200 Addressable Intelligent Module
Figure 17: M500XJ Isolator Module
The loop isolator module (M500XJ) is used to protect critical elements of
the communications loop from faults on other branches or sections of the
loop. The M500XJ continuously monitors the circuit connected to
Terminals 3 ( - ) and 4 (+). Upon power up, an integral relay is latched on.
The M500XJ periodically pulses the coil of this relay. A short circuit on
the loop resets the relay. The M500XJ sees this short and disconnects the
faulted branch by opening the positive side of the loop (Terminal 4). This
effectively isolates the faulted branch from the remainder of the loop. Once
the fault is removed, the M500XJ automatically re -applies power to the
communications loop branch. Figure 18 illustrates the use of an M500XJ
on a non-redundant communications loop. For employing M500XJs on a
redundant or isolated -redundant communications loop, see Figure 13.
Note: During a fa ult condition, the FC -2000 will register a trouble
condition for each zone mapped to the isolated loop branch.
Figure 18: Isolating Non-Redundant Communications Loops
Shorts on this branch of an isolated non -redundant communications loop
will be isolated from all devices installed both upstream of the M500XJ and
on the continuation of the loop (shown as dotted line).