AERCO BMS 168 - Manual (Page 13)

Connect the RS485 wiring at the BMS as
follows:
• Connect the positive (+) lead to the +(B)
terminal of JP11.
• Connect the negative (-) lead to the -(A)
terminal of JP11.
• Connect the shield to the SHLD terminal
of JP11.
3.4.2 RS485 Wiring At Boilers
RS485 wiring connections are made at the
RS485 COMM terminals of each boiler’s I/O
Box as shown in Figures 6 (KC1000) and
Figure 8 (Benchmark). Connect the wiring
as follows:
• Connect the positive lead to the +
terminal
• Connect the negative lead to the -
terminal
• DO NOT terminate the shields to the
Ground (G) terminal at the Boiler end of
the RS485 loop. Connect the shields of
the incoming and outgoing leads
together. The RS485 loop should only be
terminated at the BMS.
RS485 loops should not exceed 4000 feet.
Detailed wiring diagrams for RS485 Modbus
communication networks are provided in the
Modbus Communication Manual GF-114.
3.5 S
ENSOR
I
NSTALLATION
AND
W
IRING
There are two types of sensors that may be
installed -- header sensors and outside air
sensors. While an outside air sensor is
required for Indoor/Outdoor Reset mode, it
is not required for Constant Setpoint or 4-to-
20-mA modes of operation. However, it is
recommended to take full advantage of all
BMS features. The header sensor is
required for all modes of operation.
Sensor wiring and power wiring should be
run separately to reduce the chance of
electrical noise entering the sensor wiring.
3.5.1 Header Sensor
The header sensor to be used with the BMS
is a sensor that requires a well as shown in
Figure 11. When installing the sensor, use a
1/2 inch NPT tapped coupling or a 4 x 4 x
1/2 Tee fitting. Use heat-conductive grease
when installing to aid in its response. The
sensor probe must be inserted at least 2
inches into the flow of water for proper
response. The header sensor must be
installed between 2 and 10 feet downstream
of the LAST boiler in the plant’s supply
water header.
The header sensor is a thermistor type
sensor. The Resistance vs. Temperature
Chart for the sensor is provided in Appendix
F. See Figure 11 for installation details.
Shielded pair 18 AWG cable (Belden # 8760
or equiv.) is recommended for header
sensor wiring. There is no polarity to be
observed. Connect the wires from the
sensor to BMS terminals 4 and 5 on JP3.
The ground for the shield is at BMS end of
the link, not the header sensor. Connect the
ground to JP3, terminal 8 (SHIELD). The
header sensor can be installed up to 600
feet from the BMS.
3.5.2 Outside Air Sensor
The Outside Air Sensor, AERCO part no.
122662, must be mounted on the North side
of the building, shielded from direct sunlight,
and away from air intakes or outlets from
the building. See Figure 12 for a typical
installation. The sensor includes a plate for
wall mounting. Shielded pair 18 AWG cable
(Belden # 8760 or equiv.) is recommended
for sensor wiring. There is no polarity to be
observed. Connect the sensor wires to BMS
terminals 1 and 2 on JP3. Connect the
shield to JP3, terminal 3 (SHIELD) at the
BMS. The shield must not be grounded on
the sensor end. The sensor can be mounted
up to 600 feet from the BMS.
3-3