Nortec BACnet - Manual (Page 7)

3 | BACnet & LONWORKS Supplemental Install Manual
NH-EL Wiring Connections
Using the correct wiring between the humidifier and the BACnet network is important to ensure
reliable communications and reduce the impact of electrical interference.
BACnet MS/TP
For BACnet MSTP networks, the recommended wire type is 18 -24 AWG, shielded twisted pair
wire with 120 Ohm characteristic impedance. Ensuring the correct shield terminations is
necessary to prevent electrical interference. The wire shield should be terminated at either the
humidifier or the BACnet system, but not both. This allows induced current to “drain”; if the
shield is terminated at both ends it will function as a conductor and can actually increase
electrical interference. To minimize signal loss a wire run should not exceed 2000 feet at 38.4
kbps.
Table 1: BACnet MS/TP Parameters
Signal
Type
Polarity
Recommended Cable
Address
Maximum Recommended Distance
from NORTEC Humidifier
A B
Node
ID
Device
Instance
EIA-485,
2-wire Net
-
Net
+
18-24 AWG Shielded,
Twisted Pair
120
 Impedance
79* 1001*
2300 ft at 9.6 kbps
2000 ft at 38.4 kbps
*Default, may vary for multi-unit orders.