Johnson Controls FIRE-MON-17, Technical Manual, Page: 36 / 72

36 IFC Networking—Metasys Intelligent Fire Network
Ground fault detection is an option that is available for twisted pair copper
wire segments and may be provided by any IFC panel node on the network,
which is powered by a main power supply MPS-24A. It may be enabled or
disabled for each FN circuit segment through switches on the MIB.
Since the twisted pair FN communication link between adjacent nodes
can be isolated from the nodes through the MIB (transformer coupling),
a single ground fault on one of the wires will have no effect on circuit
operation. For this reason, detection of ground faults on isolated links may
not be required in some situations. Written approval from the AHJ is
required if ground fault detection is not provided.
In order to have ground fault detection on a wire segment connected to a
Fire OWS, Fire-Net NCM, or INA, one end of the segment must be
connected to an IFC panel with ground fault detection enabled on the MIB
for the segment.
Note: Fire OWSs, Fire-Net NCMs, and INAs do not provide ground fault
detection. The IFC panel provides ground fault detection when
ground fault detection is enabled on the IFC panel’s MIB.
Therefore, Switches SW1 and SW2 (see Figures 5 and 7) on the
MIB-OWS-W installed in the Fire OWS and Fire-Net NCM or on
the MIB-W installed in the INA must always be set to Off.
To maintain isolation between two nodes, only one should have ground
fault detection enabled on the segment between them.
Note: Disabling ground fault detection feedthrough at a MIB on an
IFC panel does not disable other ground fault detection provided
by the IFC panel for its addressable device SLCs, etc.
Since ground fault detection is required in Canada, it is suggested that
either fiber optic cable medium be used exclusively, or follow the
guidelines set forth within this section of the manual.
Ground Fault
Detection