AERCO SWDW68 U-Tube Double-Wall Heaters w/ECS - Manual (Page 19)

HE-
111 − INSTALLATION
Rev B Mar 2013 2-9
2.4.4 Verifying Pre-wired Connections
6. Check to ensure that all pre-wired cable harness connectors and wire leads between the Control Box
and the following ECS components are secure:
• Recirculation Pump
• Over-Temperature Solenoid
• Outlet Dual Temperature Sensor
• Mixed Temperature Sensor
7. If the ECS was ordered with the MODBUS Communication Option, proceed to step 8. Otherwise, the
ECS installation is complete.
2.4.5 Wiring the Temperature Controller to the MODBUS Control System
Step 8, below, applies to the Eurotherm, Mode 2408 Temperature Controller equipped with a MODBUS
communication board and connected to an Energy Management System (EMS), Building Automation
System (BAS) or computer. The type of communication port (RS232-9, RS232-25, or RS485) mounted on
the EMS, BAS or computer determines the relevant signal leads (Ground, Receive and Transmit) in the
control cable that you connect to the MODBUS device and the Temperature Controller, as described in
Table 2-1.
NOTE
If required, the procedure for adding a communication board to the Temperature
Controller is provided in Appendix A
Table 2-1. MODBUS Communication Signal Connections
2408 TEMP. CONTROLLER
COMPUTER CONTROL CABLE
RS232 9-PIN RS232 25-PIN RS485
SIGNAL NAME TERMINAL SIGNAL NAME PIN NO. PIN NO. PIN NO.
GROUND HD GROUND 5 7 GROUND
RECEIVE HE TRANSMIT 3 2 A(-)
TRANSMIT HF RECEIVE 2 3 B(+)
8. Refer to Table 2-1, Figure 2-8 and/or the ECS wiring diagram in Appendix B to wire the Ground (HD),
Receive (HE) and Transmit (HF) terminals of the Temperature Controller to the RS232-9, RS232-25
or RS485 connector on the EMS, BAS or computer.
Examples of cable types suitable for this purpose are: Belden 9841, 8761, 3105A, or equivalent.
Ensure that the RS232 or RS485 cable connections do not exceed the following lengths:
• RS232 Cable:
50 feet, maximum
• RS485 Cable:
4,000 feet, maximum
NOTE
For best results, DO NOT run MODBUS communication wiring in the same conduit as
power wiring which can couple excessive noise and/or hum into the MODBUS lines.