AERCO BMK 2.0 LN Natural Gas (SN G-11-1861 and above) - Manual (Page 24)

Chapter 2
Benchmark 2.0LN Low NOx Boiler
GF-123
Installation Installation, Operation and Maintenance Manual OMM-0046_0E
Page 24 of 170 AERCO International Inc.● 100 Oritani Dr. ● Blauvelt, NY 10913. ● Ph: 800-526-0288 PR1 08/20/12
Figure 2-9: Input/Output (I/O) Box Location
2.9.1 Constant Setpoint Mode
The Constant Setpoint Mode is used when it is desired to have a fixed setpoint that does not
deviate. No wiring connections, other than AC electrical power connections, are required for
this mode. However, if desired, fault monitoring or enable/disable interlock wiring can be
utilized (see paragraphs 2.9.9.1 and 2.9.10).
2.9.2 Indoor/Outdoor Reset Mode
This mode of operation increases supply water temperature as outdoor temperatures decrease.
An outside air temperature sensor (AERCO Part No. 122790) is required. The sensor MUST
BE wired to the I/O Box wiring terminals (see Figure 2-10). Refer to paragraph 2.10.1 for
additional information on outside air temperature sensor installation.
2.9.3 Boiler Management System Mode
NOTE
BMS Model 168 can utilize either pulse width modulation (PWM) or RS485
Modbus signaling to the Boiler. BMS II Model 5R5-384 and the AERCO
Control System (ACS) can utilize only RS485 signaling to the Boiler.
When using an AERCO BMS, BMS II, or ACS (AERCO Control System), the field wiring is
connected between the BMS/BMS II/ACS Panel and each Boiler’s I/O Box terminal strip (Figure
2-10). Twisted shielded pair wire from 18 to 22 AWG must be utilized for the connections. The
BMS Mode can utilize either pulse width modulation (PWM) signaling, or RS485 Modbus
signaling. For PWM signaling, connections are made from the AERCO Boiler Management
System to the B.M.S. (PWM) IN terminals on the I/O Box terminal strip. For RS485 Modus
signaling, connections are made from the BMS/BMS II/ACS to the RS485 COMM terminals on
the I/O Box terminal strip. Polarity must be maintained and the shield must be connected only at
the AERCO BMS/BMS II/ACS. The boiler end of the shield must be left floating.
For additional instructions, refer to Chapter 5, paragraph 5.6 in this manual. Also, refer to GF-
108M (BMS), GF-124 (BMS II Model 5R5-384), and GF-131 (ACS) operation manuals.