Honeywell Centra Line CLEA2026B21 - Page 7

EAGLE CONTROLLER – INSTALLATION & COMMISSIONING INSTRUCTIONS
7 EN1Z-0970GE51 R1112
RS485-1 Bias and Termination Resistors
RS485-1 is equipped with a three-position slide switch which
can be used to switch its bias resistors OFF (position “MID” –
this is the default), ON (position “BIAS”), and ON with an
additional 150 termination resistor (position “END”).
J1 J8
RS485-1
3-POSITION SLIDE SWITCH
END BIAS MID
END BIAS MID
Fig. 10. RS485-1 three-position slide switch
The recommended slide switch setting depends upon the
location and usage of the given EAGLE – see Fig. 11 and
Table 5; it also depends upon the selected communication
protocol (BACnet MS/TP or Panel Bus, respectively).
Table 5. Recommended slide switch settings
setting location / usage
END
Controllers located on both ends of bus should have
this setting.
BIAS
In small bus networks, one controller should have this
setting.
MID
All other controllers (not set to “END” or “BIAS”) on
bus should have this setting (which is the default).
47 kOHM
47 kOHM
+5V ISO
GND-1
RS485-1 (+)
RS485-1 (-)
25
26
MID (DEFAULT)
END BIAS MID
Fig. 11. RS485-1 three-position slide switch setting MID
550 OHM
550 OHM
+5V ISO
GND-1
RS485-1 (+)
RS485-1 (-)
25
26
BIAS
END BIAS MID
Fig. 12. RS485-1 three-position slide switch setting BIAS
550 OHM
150 OHM
550 OHM
+5V ISO
GND-1
RS485-1 (+)
RS485-1 (-)
25
26
END
END BI
A
S
MID
Fig. 13. RS485-1 three-position slide switch setting END
NOTE: All terminals are protected (up to 24 Vac) against
short-circuiting and incorrect wiring - except when
the 3-position slide switch is set to “END,” in which
case the terminals of the RS485-1 bus (24, 25, and
26) have no such protection. Higher voltages may
damage the device.
NOTE: According to BACnet standards, at least one BACnet
device must have its bias resistors switched ON, and
at most two BACnet devices may have their bias
resistors switched ON.
RS485-2 Bias and Termination Resistors
RS485-2 is not equipped with a slide switch. The 550 bias
resistors and 130 termination resistor of the RS485-2 are
thus always ON.