Eaton PDI JCOMM, Installation And Operation Manual

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Eaton PDI JCOMM Enclosure Installation and Operation Manual P-164001107—Rev 01 25
• There are no separate points lists for main feeds. Main feed current measurements are included in each
panelboard’s points list, whether BCMS measures main feeds with CTs or computes main feed current
from branch circuit measurements.
• If subdistribution feeds are monitored, there is a third small points list for storing data about two
subdistribution feeds. When main feeds are monitored with CTs, subdistribution feeds cannot be
monitored on that BCMS because the large circuit connections are used by the main feeds.
• Points list addresses within a BCMS must be sequential. Assign these addresses during BCMS software
setup.
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If there is no JCOMM monitor, each BCMS responds to the Modbus addresses assigned in BCMS setup. But if
the JCOMM has a monitor, the monitor is connected between the BCMS boards and the Modbus network (
Figure 16 ). The monitor intercepts and responds to Modbus addresses on behalf of the BCMSs, but it must
remap these addresses as explained in the following sections.
Figure 16. BCMS Network Connections with and without a Monitor
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In a Modbus network only the client device can poll a downstream device. There can be only one client,
typically the BMS. However, a JCOMM monitor must also poll its downstream devices.
Because there cannot be two Modbus clients, when both a monitor and BMS are present, the network must
be divided into segments at the monitor with one client per segment (
Figure 17 ).
• Upstream segment: BMS is client to the monitor; monitor is server to BMS.
• Downstream segment : monitor is client to its downstream BCMS devices.
The BMS cannot address BCMS devices downstream of the monitor because the monitor is the endpoint of
that network segment.
Instead, the monitor remaps its downstream device addresses to upstream segment addresses. When the
BMS requests data from a device downstream of a monitor, it addresses the downstream device indirectly
through the monitor. Downstream devices are only visible to the BMS through these remapped addresses.
The monitor caches data from its downstream devices. It responds to BMS requests with cached data or
retrieves fresh data from the downstream device.
Networking