Whm Modbus Network Wiring - Watts Aerco Innovation 800 User Manual

Innovation Hot Water Hot Water Boiler User Manual

8.8.3 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 8-3.
WHM
MASTER
# 1
Figure 8-3. Typical Daisy-Chain Modbus/RS485 Network
The WHMS Master does not necessarily have to be on either end of the Daisy-Chain loop
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:
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 8-4.
2. At the I/O board of the first unit in the daisy chain (not necessarily Master), 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 8-4 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.
OMM-0120_0A
GF-128-I
CHAPTER 8 – WATER HEATER MANAGEMENT
WHM
WHM
SLAVE
SLAVE
# 3
# 2
Modbus Network Wiring
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913
Phone: 800-526-0288
WHM
SLAVE
# 4
NOTE
- INTERNATIONAL
WHM
SLAVE
# 8
Page 119 of 174
11/15/2016