AERCO BMK 3.0 LN Nat. Gas APRIL 2009 - Manual (Page 18)

INSTALLATION
2-8
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
2-11). 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 can utilize only RS485
signaling to the Boiler.
When using an AERCO Boiler Management
System (BMS), the field wiring is connected
between the BMS Panel and each Boiler’s I/O
Box terminal strip (Figure 2-11). 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 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.
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 Model 168) and GF-124 (BMS II
Model 5R5-384), BMS -Operations Guides.
2.9.4 Remote Setpoint and Direct Drive
Modes
The Benchmark 3.0 Boiler can accept several
types of signal formats from an Energy
Management System (EMS), Building
Automation System (BAS) or other source, to
control either the setpoint (Remote Setpoint
Mode) or firing rate (Direct Drive Mode) of the
Boiler. These formats are:
• 4 to 20 mA/1 to 5 VDC
• 0 to 20 mA/0 to 5 VDC
• PWM – (Pulse Width Modulated signal. See
para. 2.10.4)
• Network (RS485 Modbus. See para. 2.10.7)
While it is possible to control a boiler or boilers
using one of the previously described modes of
operation, it may not be the method best suited
for the application. Prior to selecting one of
these modes of operation, it is recommended
that you consult with your local AERCO
representative or the factory for the mode of
operation that will work best with your
application. For more information on wiring the
4 to 20 mA / 1to 5VDC or the 0 to 20 mA / 0 to 5
VDC, see paragraph 2.9.3.
2.9.5 Combination Mode
NOTE
Only BMS Model 168 can be utilized for
the Combination Mode, not the BMS II
(Model 5R5-384).
With a Combination Mode unit, field wiring is
between the unit’s I/O Box wiring terminals, the
CCP (Combination Control Panel), and the BMS
Model 168 (Boiler Management System). The
wiring must be accomplished using twisted-
shielded pair wire from 18 to 22 AWG. Polarity
must be maintained. For further instructions and
wiring diagrams, refer to the GF-108 Boiler
Management System Operations Guide and the
CCP-1 data sheet.
2.10 I/O BOX CONNECTIONS
The types of input and output signals and
devices to be connected to the I/O Box terminals
shown in Figure 2-11 are described in the
following paragraphs.
CAUTION
DO NOT make any connections to the
I/O Box terminals labeled “NOT
USED”. Attempting to do so may
cause equipment damage.
2.10.1 OUTDOOR SENSOR IN
An outdoor air temperature sensor (AERCO Part
No. 122790) will be required primarily for the
Indoor/Outdoor reset mode of operation. It can
also be used with another mode if it is desired to
use the outdoor sensor enable/disable feature.
This feature allows the boiler to be enabled or
disabled based on the outdoor air temperature.