Trane E50 Series - RS-485 Communications

BAS-SVX076C-EN
23
RS-485 Communications
The RS-485 secondary port allows the power meter to be connected in a daisy chain with up to
63, 2–wire devices.
–
+
S
Shielded Wire
120 Ω terminators on the rst/last devices of daisy chain
Notes:
• The voltage and current ratings on the terminals are compliant with the requirements
of the EIA RS-485 communications standard.
• The RS-485 transceivers are ¼ unit load or less.
• RS-485+ has a 47 kΩ pull up to +5V, and RS-485- has a 47 kΩ pull down to
Shield (RS-485 signal ground).
• Wire the RS-485 Bus as a daisy chain from device-to-device, without any stubs.
Use 120 Ω termination resistors at each end of the bus (not included).
• Shield is not internally connected to Earth Ground.
• Connect Shield to Earth Ground somewhere on the RS-485 bus (only at one point).
For all terminals on E50 meters:
• When tightening terminals, apply the correct torque: 0.37-0.44 ft·lb (0.5-0.6 N·m).
• Use 14-24 gauge (2.1-0.2 mm
2
) wire.