88
Cables
12.3
Typical Optical Power Budget
•
50/125
μ
m: 9.6 dB
•
62.5/125
μ
m: 15 dB
12.3.1
Connecting Fiber Optic Cables
For instructions on wiring the FOM-2000-UM, see LT-6907 FOM-2000-UM Installation and
Operation Manual.
12.4
Ground Fault Reporting
The FleX-Net™ system reports ground faults as required by UL, ULC, and FM. Mircom has
enhanced ground fault reporting to aid the technician in identifying which lead of a pair of wires
is in contact with the ground. To this end, the ground fault report on the panel includes
information about polarity (positive or negative).
•
SLC (signaling line circuits) wires and IDC (input detection circuits) wires:
The
positive ground fault or negative ground fault report on the panel points the technician to
the fault directly.
•
NAC circuits:
The polarity of the ground fault is reversed in the panel report because in
normal supervisory condition, the NAC circuits are driven in the opposite polarity.
•
Annunciator and network connections that use electrical industry standard RS-
485 connections:
The panel reports a ground fault on either lead of these connections
as negative. This is a result of the low voltage circuitry used for such signaling. Neither
the positive lead nor the negative lead of the RS-485 line is of a high enough voltage
level to accurately differentiate between a positive or negative ground fault, so in the
case of a ground fault on either lead of the RS-485 line, only a negative ground fault is
reported.
12.5
Ground Fault Detection
In certain applications, a large number of wires connected to the same panel can cause a high
capacitance to ground, which can cause the FleX-Net™ system to report false intermittent
ground faults.
If the system reports intermittent ground faults when there is no ground fault, turn on
Alternate
Ground Fault Detection
in the Configurator. This compensates for the errors caused by high
capacitance to ground in cables.
Turn on Alternate Ground Fault Detection
1. In the Configurator, open the version of the job that is active on the panel.
2. Select the node that is reporting ground faults.
3. Check
Alternate Ground Fault Detection
at the bottom of the window.
4. Click
Panel
>
Send Job
to send the job to the Fire Alarm Control Panel.