Honeywell CENTRA LINE EAGLEHAWK NX - BACNET MS;TP BUS CONNECTION; BACnet MS;TP Bus Considerations; Connecting EAGLEHAWK NX via its RS485-1 Interface to a BACnet MS;TP Bus

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
24V~ 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
END BI
A
S
MID
BACnet
Module #1
BACnet
Module #2
RS485 +
RS485 -
GND
BACnet
Module #3
BACnet
Module #4
BACnet
Module #N-1
BACnet
Module #N
RS485 + RS485 + RS485 +
RS485 - RS485 -
GND GND GND
R T
RS485 -
RS485 +
RS485 -
GND
*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.