Watts AERCO Benchmark 2.0 LN Operating & Maintenance Instructions page 16

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
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 2.7.3.
2.6.4 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
connected 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 done using a
shielded twisted pair of 18- 22 AWG wire and
polarity must be maintained.
instructions and wiring diagrams, refer to the
GF-108 Boiler Management System Operations
Guide and the CCP-1 data sheet.
2.7 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 2.9 are described in the
following paragraphs.
CAUTION!
DO NOT make any connections to the I/O
Box terminals labeled
Attempting to do so may cause equipment
damage.
2.7.1 OUTDOOR SENSOR IN
An outdoor air temperature sensor (AERCO Part
No. 122790) will be required mainly 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.
The factory default for the outdoor sensor is
DISABLED. To enable the sensor and/or
choose an enable/disable outdoor temperature,
see the Configuration menu in Chapter 3.
work best with your
For further
"NOT USED".
INSTALLATION
The outdoor sensor may be wired up to 200 feet
from the boiler It is connected to the OUTDOOR
SENSOR IN and SENSOR COMMON terminals
in the I/O box (see Figs. 2.8 and 2.9). Wire the
sensor using a twisted shielded pair cable of 18-
22 AWG wire. There is no polarity when
terminating the wires. The shield is to be
connected only to the terminals labeled SHEILD
in the I/O box. The sensor end of the shield must
be left free and ungrounded.
When mounting the sensor, it must be located
on the North side of the building where an
average outside air temperature is expected.
The sensor must be shielded from direct sunlight
as well as impingement by the elements. If a
shield is used, it must allow for free air
circulation.
2.7.2 AUX SENSOR IN
The AUX SENSOR IN terminals can be used to
add an additional temperature sensor for
monitoring purposes. This input is always
enabled and is a view only input that can be
seen in the operating menu. The sensor must be
wired to the AUX SENSOR IN and SENSOR
COMMON and must be similar to AERCO
BALCO wire sensor P/N 12449. A resistance
chart for this sensor can be found in APPENDIX
C.
2.7.3 ANALOG IN
The ANALOG IN + and – terminals are used
when an external signal is used to drive the
firing rate (Direct Drive Mode) or change the
setpoint (Remote Setpoint Mode) of the Boiler.
Either a 4 to 20 mA / 1 to 5 VDC or a 0 to 20 mA
/ 0 to 5 VDC signal may be used to vary the
setpoint or firing rate. The factory default setting
is for 4 to 20 mA / 1 to 5 VDC, however this may
be changed to 0 to 20 mA / 0 to 5 VDC using the
Configuration Menu described in Chapter 3. If
voltage rather than current is selected as the
drive signal, a DIP switch must be set on the
PMC Board located inside the Control Box.
Contact the AERCO factory for information on
setting DIP switches.
All supplied signals
(ungrounded) signals. Connections between the
source and the Boiler's I/O Box must be made
using twisted shielded pair of 18 –22 AWG wire
such as Belden 9841(see Fig. 2.9).
must be maintained and the shield must be
connected only at the source end and must be
left floating (not connected) at the Boiler's I/O
Box.
must be floating
Polarity
2-7