Basic Documentation

BACnet networks with MS/TP trunks
Application examples
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5.4.2 Network for mid-sized to large BACnet MS/TP project structured
with centralized primary plants
Example for planning and implementing a project.
Demand
● New office building with room automation for 424 rooms over 4 floors as well as preparing the
appropriate primary plants.
● Each floor is leased by another tenant and has its own occupancy and use, i.e. the room operating
mode as well as associated room setpoints, lighting per floor with central operation, and emergency
function.
● Blinds control for each facade including protection, service, and emergency function.
● Central weather station, demand-controlled control of primary plants.
● Schedulers together with a calendar for room operating modes and lighting for each floor, superposed
functions on a monitoring device.
● Primary plants for air handling, heat generation and distribution as well as central distribution of
refrigeration in an equipment room.
● Primary plants and general: 5 PXC100-E.D und 5 PXC00-E.D
● Desigo room automation: 406 DXR2…
● Visualization, operating and monitoring Desigo CC
● Monitoring network components via SNMP
Planning and implementation, IP network
Core level
Core Switch (Managed Layer 3) as the network core, interface for remote maintenance, and office network
as well as building additional IP segments or as a redundant backbone.
Distribution level
Managed layer 2 switches are planned on the distribution level, in the riser zones, i.e. floor distributors that:
● Are connected with copper cabling.
● Ensure that Desigo room automation stations from the given floor are located on its own VLAN and
therefore isolated from other Desigo room automation stations on other floors for the purposes of local
BACnet broadcasts.
● You can configure port mirroring of each VLAN for network diagnostics and troubleshooting.
Edge level
Only unmanaged layer 2 switches are planned as edge switches. BACnet MS/TP networks can have a max.
cable length depending on the set baud rate. If the overall length is, however, exceeded, a new BACnet
network must be created and connected via a BACnet MS/TP IP router to BACnet/IP over the Ethernet.
The rules apply again for BACnet/IP networks, i.e. the Ethernet network must be installed as an
unmanaged layer 2 switch. A PXC.. can integrated in the given zones to control primary plants, depending
on building planning.