EAGLE CONTROLLER – INSTALLATION & COMMISSIONING INSTRUCTIONS
EN1Z-0970GE51 R0918 28
BACNET MS/TP BUS CONNECTION
The EAGLE 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) and system GND (terminals 19+37)
BACnet MS/TP Bus Considerations
RS485-1 (isolated)
˗ Max. BACnet MS/TP bus length: 1200 meters (9.6 – 76.8 kbps) or 1000 meters (115.2 kbps) (see also section "RS485
Standard" on pg 9).
˗ Use only shielded, twisted-pair cable and daisy-chain topology.
˗ Must conform to EIA-RS485 cabling guidelines.
RS485-2 (non-isolated)
˗ Max. BACnet MS/TP bus length: 1200 meters (9.6 – 76.8 kbps) or 1000 meters (115.2 kbps) (see also section "RS485
Standard" on pg 9).
˗ 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.
Max. no. of BACnet MS/TP devices
˗ The max. number of BACnet MS/TP devices per RS485 interface depends on the given traffic. The current limit is 200
messages per minute. The max. number of room controllers is 20, assuming a typical traffic of 10 messages per minute.
In the case of non-room applications, the max. number of MS/TP devices can be up to 32 (including the EAGLE, itself) –
provided the traffic does not exceed 200 messages per minute. Following the same logic, the max. number of BACnet
MS/TP devices per EAGLE is 40 room controllers or 62 non-room MS/TP devices – provided the traffic does not exceed
200 messages per minute per RS485 interface.
Connecting RS485-1 to BACnet MS/TP Buses
With regards to Fig. 42 through Fig. 44, please note the following:
NOTE: Always power each EAGLE and the connected BACnet MS/TP modules via separate transformers.
NOTE: For "L," see section "RS485 Standard" on pg. 9.
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. 9.
Example 1: Single EAGLE 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 OHM 150 OHM 550 OHM
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
EAGLE
*CONNECT GND, IF AVAILABLE.
RS485-1
120 Ohm
END
END
BIAS
MID
Fig. 42. Connection of RS485-1 to a BACnet MS/TP Bus
The termination resistor must be inserted directly into the terminals of the last BACnet MS/TP module.
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