Johnson Controls Metasys Intelligent Fire Network Technical Manual page 37

Point-To-Point
Configuration
Ground Fault
Considerations
The following paragraphs highlight ground fault detection considerations
for point-to-point and bus wire configurations. In the examples that follow,
the MIB-WF may be used in place of the MIB-W.
In a point-to-point segment without repeaters, enable ground fault
detection in only one of the two nodes powered by an MPS-24A to
monitor the FN segment between the two nodes. In Figure 12, the left node
is an IFC panel and will therefore provide ground fault detection for the
FN segment between the two nodes. On the MIB node to the left, SW2 is
set to the On position to enable ground fault feedthrough detection on
MIB-W Port B. The corresponding Port A switch, SW1, of the right
MIB-W is set to the Off position, disabling ground fault detection
feedthrough from the node on the right. The node on the right can be any
network node, including another IFC panel, Fire OWS, Fire-Net NCM, or
remotely powered INA.
With the switches set in this manner, the ground fault detection feature of
the power supply located in the node to the left is monitoring the
FN segment between the two nodes.
A
Ports
SW2
Ground Fault
Detection
Enabled
MIB-W
IFC Node
Figure 12: Point-To-Point Ground Fault Detection
If an RPT-W is employed, two ground fault detection schemes are possible
within a point-to-point configuration. One (Example 1 and Figure 13) or
both (Example 2 and Figure 14) nodes may provide ground fault detection,
depending on the number of the repeaters and the setting of the repeater
feedthrough switch (SW3) at each repeater.
Example 3 and Figure 15 show the proper application of ground fault
detection when a number of repeaters are positioned on the FN between
two nodes.
Twisted Pair Wire
B
On
Power
Supply
IFC Networking—Metasys Intelligent Fire Network
A B
Ports
SW1
Off
Ground Fault
Detection
Disabled
MIB-W
Power
Supply
gfd1
Node
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