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EAGLEHAWK NX CONTROLLER – INSTALLATION & COMMISSIONING INSTRUCTIONS
EN1Z-1039GE51 R1218
40
BACNET MS/TP BUS CONNECTION
The EAGLEHAWK NX controller features two RS485 interfaces to which BACnet MS/TP devices can be connected: RS485-1
(consisting of push-in terminals 24 [GND-1], 25, and 26) and/or RS485-2 (consisting of push-in terminals 29, 30, and 31 [GND-
2]).
NOTE:
GND-2 is internally connected with 24V-0 (terminal 1)
BACnet MS/TP Bus Considerations
RS485-1 (isolated)
˗
Max. BACnet MS/TP bus length: 1200 meters (9.6 – 78.8 kbps) or 800 meters (115.2 kbps) (see also section "RS485
Standard" on pg. 10).
˗
Use only shielded, twisted-pair cable and daisy-chain topology.
˗
Must conform to EIA-RS485 cabling guidelines (see section "EIA 485 Cable Specifications" on pg. 35).
RS485-2 (non-isolated)
˗
Max. BACnet MS/TP bus length: 1200 meters (9.6 – 78.8 kbps) or 800 meters (115.2 kbps) (see also section "RS485
Standard" on pg. 10).
˗
Use only shielded, twisted-pair cable and daisy-chain topology.
˗
Ground noise should not exceed the EIA-485 common mode voltage limit.
˗
Must conform to EIA-RS485 cabling guidelines.
˗
Should not extend beyond a single building.
Connecting EAGLEHAWK NX via its RS485-1 Interface to a BACnet MS/TP Bus
With regards to Fig. 44 through Fig. 46, please note the following:
NOTE:
Always power each EAGLEHAWK NX controller and the connected BACnet MS/TP modules via separate transformers.
NOTE:
For "L," see section "RS485 Standard" on pg. 10.
NOTE:
If any of the devices are electrically isolated, it is recommended that those devices be connected to signal ground. See
section "RS485 Standard" on pg. 10.
Example 1: Single EAGLEHAWK NX Controller and Connected BACnet Modules (with inserted termination
resistor)
1 2
24
V~
24
~
0
242526
F1
230 V
24 V
L
GND-1
GND-1
+5V
ISO
RS485-1 (+) RS485-1 (-)
550 kOHM
150 kOHM
550 kOHM
END
EN
D
BI
A
S
MID
BACnet
Module #1
BACnet
Module #2
RS
48
5
+
RS
48
5
-
GN
D
BACnet
Module #3
BACnet
Module #4
BACnet
Module #N-1
BACnet
Module #N
RS
48
5
+
RS
48
5
+
RS
48
5
+
RS
48
5
-
RS
48
5
-
GN
D
GN
D
GN
D
R
T
RS
48
5
-
RS
48
5
+
RS
48
5
-
GN
D
*CONNECT GND, IF AVAILABLE.
120 OHM
EAGLE-
HAWK NX
Fig. 44. Connection of a single EAGLEHAWK NX controller via its RS485-1 interface to a BACnet MS/TP Bus
The termination resistor must be inserted directly into the terminals of the last BACnet MS/TP module.