Nordic ATWC Series, Инструкция по установке и обслуживанию, Страница: 14 / 106

PRELIMINARY: 24-Sep-2021 Page 14 002536MAN-00
Aquastat Connections (Optional)
Most installations will use the internal
Setpoint Control
routine to control buffer tank temperature, in which case no aq-
uastat is required. However, an aquastat or aquastats can be
used if required, for example if heating two loops with different
setpoint temperatures. This is
Signals
or
Hardwired Control
.
C, R, and O connections are located on the main ter-
minal strip. Y1A is located at right side towards the top of the
control board. This is shown on the wiring (SCH) diagram in the
Model Specific Information section. The external device
needs to send the 24VAC signal from R back to Y1A to call for
the single capacity stage of hydronic heating, and R back to O
to activate cooling mode. C is the common or ground terminal
for use in powering the external device.
TABLE 11 - Aquastat (Signals Control) Connections
Signal Description
O Cooling Mode (Reversing Valve)
C 24VAC common (ground)
R 24VAC hot
Y1A Compressor ON (Part Load)
Use an 18ga cable.
Disable Switch (field installed)
A switch to disable demand from the control system may
be installed. On control board, jumper COM_IN to GND, and
toggle 12VDC to IN_SPARE to disable. See the main wiring
diagram in the Model Specific Information section.
Outdoor Unit: Signal Connections
The speed of the fans and the two heating mode expan-
sion valves (EEVs) in the outdoor unit must be controlled by the
control board in the indoor unit, and a temperature sensor must
be read. For ATWC/ATW2 series, this is done by MODBUS
communications between the main control board in the indoor
unit and a small daughter board in the outdoor unit. So the
number of required signal wires is reduced.
Connect the supplied double twisted pair shielded outdoor
rated cable between the terminal strips in the indoor and
outdoor units. The shield itself is connected only to the indoor
unit; do not connect the shield ground to the outdoor unit
(there is no terminal for it). Cut the shield short at the cable
sheath in the outdoor unit.
TABLE 10 - Outdoor Unit Signal Connections
Signal Description
A
MODBUS Communications
(use 1 twisted pair)
B
12
VDC
GND
Shield
Cable shield: connect only to the indoor
unit. In the outdoor unit, cut the shield
short at the cable sheath.
Use provided double twisted pair
shielded
outdoor
rated cable.
Power to MODBUS board in outdoor unit
AVOID INSULATION NICKS ON INDIVIDUAL
OUTDOOR UNIT SIGNAL WIRES
SLICE A LINE ALONG WIRE SHEATHING TO-
WARDS THE END, THEN PULL IT AWAY FROM
THE WIRES BEFORE CUTTING OFF.
DO NOT CUT A CIRCLE WITH UTILITY KNIFE
BEFORE SEPARATING SHEATHING FROM BUN-
DLED SIGNAL WIRES.
Defrost Indicator (field installed)
A 24VAC signal is available for an externally installed
indicator, which is active when the heat pump is in defrost
mode. This may be useful for the building operator or home-
owner, to know when buffer tank is being cooled instead of heat-
ed.
The indicator may be installed between terminals SH
and C(SH) at the lower left side of control board.