AERCO Innovation (G-13-1854 and above) - Manual (Page 112)

Innovation Water Heaters Installation, Operation & Maintenance Manual
CHAPTER 9 – WATER HEATER MANAGEMENT
Page 112 of
196 AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913
OMM-0078_0J
PRI: 11/22/2013
Phone: 800-526-0288
GF-128
9.5.2 WHM Modbus Network Wiring
As previously mentioned, all units being controlled by the WHM will be connected to a RS485
Modbus Network. All Modbus networks are wired in a daisy-chain configuration using a
Master/Slave scenario as shown in Figure 9-3.
WHMS
SLAVE
#1
WHMS
MASTER
(See Note)
WHMS
SLAVE
#2
WHMS
SLAVE
#3
WHMS
SLAVE
#4
WHMS
SLAVE
#5
NOTE: The WHMS Master does not necessarily have to be on either end of the Daisy-Chain loop,
Figure 9-3. Typical Daisy-Chain Modbus/RS485 Network
Any one of the C-More WHM units included in the Modbus network can be the Master.
However, it is recommended that you decide which unit will be the Master and which will be the
last unit on the daisy-chain prior to performing the wiring connections. This will simplify wiring
connections and Modbus address assignments,
Modbus network wiring connections must be made using shielded twisted-pair wiring, (18 – 24
AWG) such as Belden #9841, #3105A, #8760, or equivalent. The Modbus wiring connections
are made at the RS485 COMM terminals on the I/O board included with each C-more Control
System.
Connect the Modbus wiring as follows:
Modbus Network Wiring
1. Starting at the first unit, connect the twisted, shielded pair cable to the RS485 Comm plus
(+) and minus (-) terminals on the left side I/O board as shown in Figure 9-4.
2. At the Modbus Master I/O board, activate the DIP switch labeled “MODBUS TERM” by
placing it in the up position. This will connect a termination resistor across the terminals at
the source end.
3. Refer to Figure 9-4 and run the shielded cable to the next unit in the daisy-chain and
connect the + and – wire leads (+ to +, - to -). DO NOT terminate the shield of the RS485
Comm leads to the SHIELD terminal at the Slave. Instead, connect the shields of the
incoming and outgoing RS485 leads together.
4. Continue connecting the + and - wire leads and shields for the remaining units as
described in step 3 for the remaining Slave units in the chain.
5. At the end unit in the chain, activate the DIP switch labeled “MODBUS TERM” by placing
it in the up position. This will ensure that the termination resistors are activated at both
ends of the loop.