MERLIN NX ROOM CONTROLLER – INSTALLATION & COMMISSIONING INSTRUCTIONS
EN1Z-1035GE51 R0319
16
COMMUNICATION INTERFACES
BACnet MS/TP Interface
The controller features an RS485 interface (RLxN: terminals
62, 63, and 64; RSxN: terminals 40, 41, and 42) suitable for
BACnet MS/TP communication. The terminal block containing
it is black. The cable length affects the baud rate. See Table
11.
Table 11. Baud rate vs. max. cable length
baud rate
max. cable length (L)
9.6, 19.2, 38.4, 57.6, and 76.8 kbps
1200 m
115.2 kbps
800 m
For information on wire gauge, max. permissible cable length,
possible shielding and grounding requirements, and the max.
number of devices which can be connected to a bus, refer to
standard EIA-485.
Connecting to BACnet MS/TP Buses
The controller communicates via its BACnet MS/TP interface
with other BACnet MS/TP-capable devices (e.g., other room
controllers or plant controllers like the EAGLE / Excel Web II).
In doing so, the following considerations should be taken into
account.
▪ Max. BACnet MS/TP bus length (L): See Table 11.
▪ Twisted-pair cable, e.g.:
- AWG 18;
- J-Y-(St)-Y 2 x 2 x 0,8;
- CAT 5,6,7 cable – use only one single pair for one
bus;
- Belden 9842 or 9842NH);
and daisy-chain topology.
▪ Must conform to EIA-RS485 cabling guidelines and
ANSI/ASHRAE Standard 135-2010.
▪ Max. no. of BACnet MS/TP devices (including the Master)
per BACnet MS/TP channel: 31 (= "N" in Fig. 23).
L
END
EN
D
BI
A
S
MI
D
CLME-RSxN
CLME-RLxN
25 26
62 63 64
BACnet MS/TP
DEVICE #1 (MASTER)
BACnet MS/TP
DEVICE #2
BACnet MS/TP
DEVICE #3
BACnet MS/TP
DEVICE #4
BACnet MS/TP
DEVICE #N
40 41 42
120
Ω
24
GND
GND
RS485 -
RS485 -
RS485 +
RS485 +
C1+
C1+
C1-
C1-
GND
GND
TWISTED
PAIR
NOTE 1
EAGLE / Excel Web II
PLANT CONTROLLER
Fig. 23. Connection to a BACnet MS/TP Bus
NOTE 1:
If any of the devices are electrically isolated, it is
recommended that those devices be connected to
signal ground.
NOTE 2:
The 120-Ohm termination resistor must be inserted
directly into the terminals of the final BACnet MS/TP
device.
NOTE 3:
If shielding is used, the shielding of each individual
bus segment should be separately connected at one
end to earth.
RJ45 Connector for BACnet WiFi Adapter
A BACnet WiFi Adapter can be connected to the controller's
RJ45 connector in order to establish wireless communication
with a PC with Niagara so that the application engineer can
commission the controller.
NOTE:
When the BACnet WiFi Adapter is connected to the
controller's RJ45 connection, it is powered by the
controller. It is then prohibited to simultaneously
power the BACnet WiFi Adapter via a wall adapter.
When, on the other hand, the BACnet WiFi Adapter
is instead connected to the controller's BACnet
MS/TP interface, it is prohibited to simultaneously
use an RJ45 plug; instead, the BACnet WiFi Adapter
must then be powered by a wall adapter (standard 5-
V USB wall adapter with micro USB connector).
See also corresponding Technical Literature listed in Table 15
on pg. 23.
CLME-RLxN
(CLME-RSxN)
8 7 6 5 4 3 2 1
7 8
4
2,3,
5,6
RJ45 CONNECTOR
INTERNAL
CONNECTIONS
BACnet MS/TP
62
(40)
C1+
63
(41)
C1-
64
(42)
GND
1 = DETECT
2 = GND
3 = GND
4 = 24VAC
5 = GND
6 = GND
7 = C1+
8 = C1-
BACnet WiFi
ADAPTER
Niagara
workbench
RJ45
PLUG
Fig. 24. RJ45 interface and BACnet WiFi Adapter
CAUTION
It is permitted to connect
only
the BACnet WiFi
Adapter to this RJ45 connector. Do
not
connect IP!
Sylk Bus
Sylk Bus-capable devices (e.g., the CLCMTR40x/T42x) can
be connected to the controller's Sylk Interface (RSxN: ter-
minals 20 and 21; RLxN: terminals 30 and 31). Specifically:
▪ A max. of one wall module can be connected.
▪ The Sylk Bus is single pair, and polarity-insensitive.
▪ Max. current provided at the Sylk Bus interface: 96 mA.