Network and device requirements and limitations
The following requirements apply to the MR5 controller for network communications:
• The controller requires an RS485 bus cable to connect to a BACnet or Verasys network.
• When you connect to a network, you must set the MS/TP connectivity for the controller to
BACnet or Verasys as appropriate.
• The controller does not have an end-of-line (EOL) switch. You must connect a 220 ohm EOL
resistor to an ADPT-MR5 adapter to configure it as an EOL controller. See Figure 26.
Communications adapter wiring connections
The following image shows the MR5 RS485 adapter SHD, REF, -, and + field wiring connection ports.
Table 26 describes the connection ports and the best practice wiring sizes.
Figure 25: MR5 RS485 adapter field wiring connections
Table 26: MR5 RS485 adapter field wiring connections
Terminal
label
Description
Wire size
SHD
Shield connection: the SHD is a dead-end or blank terminal
that you use to connect all the network cable shield drains.
REF
RS485 BACnet signal common or reference
-
+
The RS485 communications terminal block enables a
network connection to RS485 MS/TP BACnet networks,
including Johnson Controls Verasys networks.
0.14 mm
2
to 0.34 mm
2
(26 AWG to 22 AWG)
stranded wires and
twisted-leads cable
Wiring the RS485 communications port to a communications network
About this task:
Follow these steps to wire the RS485 communications port to a communications
network on an isolated RS485 bus. The isolated cable shield drain (SHD) terminal on the network
terminal block splices the cable shields along the daisy chain. See Figure 26.
1. Set the EOL switch on the master device to off unless the master device is also an EOL device.
2. Set the MS/TP connectivity of the controller to BACnet or Verasys as appropriate.
3. Connect the network terminal block on the ADPT-MR5-RS485 adapter to the other network
devices in a daisy-chain configuration using 3-wire twisted, shielded cable.
4. Determine the physical location of the MR5 controller connection on the daisy-chain network
trunk.
5. If the MR5 controller is an EOL terminating device on the network trunk, connect the 220 ohm
resistor between the + and - terminals on the adapter. This configures the adapter as an EOL
MR5 Series Panel Mount Case Controller Technical Bulletin
58
Discontinued
