AERCO XPC GATEWAY Communications - Manual (Page 60)

GATEWAY COMMUNICATIONS MANUAL
60
+
G
-
TERMINATE SHIELD
AT BMS II ONLY
C-MORE I/O BOX
R
S
48
5 C
O
M
M
FIRST UNIT
S
H
IE
L
D
TIE TOGETHER WITH
SHIELDS OF OTHER
C-MORE UNITS
RED (+)
BLUE
(-)
RED (+)
BLUE (-)
SHLD
(JP7, TERM. #3)
485 A
485 B
ISO GND
BMS II RS485 (JP6)
Figure 3-14. BMS II Connections to C-More Controller
NOTE
Refer to AERCO Instruction Manual GF-124 for additional information on
BMS II keypad functions, displays and password entries.
5. With the BMS II in the RS232 MENU, scroll to the MODBUS PASS THRU menu option.
6. If ENABLED is not displayed in the second line of the display, press the
CHANGE key and toggle the
display to ENABLED
using the ▲ or ▼ arrow key. Press the ENTER key to store the setting.
7. With MODBUS PASS THRU set to ENABLED, both the BMS II and the boilers can now be
monitored.
NOTE
The Gateway Response Time for Modbus must be adjusted to 2 seconds in
order for the communication to work efficiently. This is due to the extra lag
in communications to the boiler when going through the BMS II. Since the
BMS II control operations take priority, it may delay the processing of a
Gateway command by a second or two depending on what it is doing at the
moment.
3.3.3 Modulex Boilers Being Network-Controlled by a BMS II
When the BMS II is controlling C-More Boilers on the RS485 Modbus network it is the single “Master”
device. No other device, such as the XPC Gateway or a BAS can assume control of the network.
However, the BMS II also functions as a communications Gateway which permits a BAS to monitor the
BMS II as well as the boilers on the Modbus network. This is accomplished utilizing the RS232 port of the
BMS II.
If the BAS being utilized supports Modbus RTU protocol, it can be connected to the BMS II either directly
or via a RS485-to-RS232 converter. However, if the BAS does not support Modbus protocol and utilizes
BACnet, N2 or LonWorks, the AERCO XPC Gateway must be used as described below.