CLASS 320 METER
6.10 Modbus RTU Wiring
The Class 320 Modbus option meter communicates with building automation
equipment over a 2-wire (3-conductor) RS-485 network using Modbus RTU protocol.
The meters are networked in a daisy-chain configuration with BELDEN 1120A cable or
equivalent required. The cable rating of 600V allows the RS-485 network to be
connected to 480-volt meters. Up to 52 meters can be installed on a network string.
The maximum combined length of all daisy-chained cables must not exceed 4000 feet.
The meter-to-network connection is through the 3-screw terminal which is located on
the Main Power Board of the meter. Tighten the terminals to 2.2 in-lb.
Fig. 18. RS-485 Terminal.
The meter is shipped with a Modbus ID number of 02. NOTE: Modbus address must
be changed to 01 for open protocol for BACnet (Optional) to function as specified. This
must be changed if the network has more than one meter installed. The change must
be done before the meter is introduced into the network. The meter can be numbered
from 1 to 247. There can be no duplicate numbers on a network, so caution must be
taken when assigning a meter ID number prior to its installation on the RS-485