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9.7 - RS-485 Network Biasing: Lenze SMVector VFDs (Powerfoil
®
8 & Basic 6
®
fans)
Depending on the design of the RS-485 transmitters and receivers, biasing resistors may be required for proper data transmission. The
biasing resistors keep the data lines on the system at a fixed level while the transmitters are in an idle state. Without these resistors,
data corruption or data packet loss can occur. The SMVector drives fall within these requirements; therefore,
a pair of 680 Ω, ¼ W
resistors must be installed on either the first or last SMVector drive in the network series.
Due to the presence of a 120 Ω
resistor at the end of the line, Big
Ass
Fans recommends installing the 680 Ω resistors at the first fan location to prevent clutter on the
terminal strip.
9 - Big
Ass
Fans Electrical Installation (cont.)
2 TXA TXB 11
AI 2
2 TXA TXB 11
AI 2
CAUTION: Risk of short circuit exists
between terminals TXA and TXB with
resistors installed. Isolate as necessary.
Modbus cable
from Gateway
Modbus cable
out to next fan
(if applicable)
Terminal TXA = Data(-)/Gray
Terminal TXB = Data(+)/White
Terminal 2 = Shield
Install a 680 Ω resistor between terminals 2 and
TXA. Install a second 680 Ω resistor between
terminals TXB and 11.
Note: T
he wire colors shown are applicable to Windy City Wire Modbus cable only. Other cable types may differ. Take note of color/
polarity if using a different model of cable.
680 Ω, ¼ W
680 Ω, ¼ W
bare
white
gray
white
bare
gray
