Nordic ATWC Series, Installation And Service Manual, Page: 13 / 106

PRELIMINARY: 24-Sep-2021 Page 13 002536MAN-00
Setpoint Control Connections
If using the on-board Setpoint Control routine with sam-
pling to control buffer tank temperature, no external temperature
probe or aquastat is required. In this case, only one control
connection is required, a dry contact from R to O on terminal
strip to switch the heat pump into cooling mode. C may be used
in powering relays as shown in diagrams on following pages.
Note that in a one tank heating/cooling system, the
O
signal must be continuously provided during cooling sea-
son. If it toggles with demand, the tank will be repeatedly
heated and cooled, resulting in high power usage.
TABLE 9 - Setpoint Control: Aux. Connections
Signal Description
R
D1
D2
Hydronic Auxiliary Contactor
D1
Hydronic Auxiliary dry contacts
D2
H1
Hydronic Auxiliary ONLY dry contacts
(for high temperature auxiliary heat)
H2
Use a 2-conductor 18ga cable.
Connect with wire jumper and also connect to
Hydronic Auxiliary Contactor
TABLE 8 - Setpoint Control Connections
Signal Description
C 24VAC common (ground)
R 24VAC hot
O Cooling Mode (Reversing Valve)
Use a 3-conductor 18ga cable.
An external temperature probe may be used with the on-
board Setpoint Control routine; this is the required method if
using an ultra-high temperature boiler in parallel with heat
pump on terminals H1-H2 . Or two probes (one for hot tank
and one for cold tank) may be used. This is HTS/CTS Setpoint
Control; see Piping and Operation sections for details.
Setpoint Control: Aux. Connections
When using Setpoint Control, there are 3 methods for acti-
vating hydronic auxiliary heat. See diagram on a following
page.
First, if using a heating device that doesn’t have its own
electronic controller or control transformer, e.g. a bare heating
element in the buffer tank: connect coil of an external contactor
to R and D2 on terminal strip, and jumper R to D1 as shown.
This contactor can then be used by the heat pump to toggle high
voltage power to the heating device when auxiliary heat is re-
quired. Default will be OFF when heat pump is powered off.
Second, a dry contact on terminals D1 and D2 is available,
to actuate a heating device that has its own controller and trans-
former. In general, these types of devices will have their own
electronic temperature controller. Connection will be made to
that device’s E-E terminals or similar. D1-D2 defaults to ON
when heat pump is powered off. Therefore, it is necessary to
set the temperature control on the external heating device to a
limiting value, e.g. 125°F, and adjust its settings so it is only
activated by the heat pump’s controller. This method should be
used for the Thermo2000 AltSource tank that is available
from Maritime Geothermal as an accessory; see the setup
instruction sheet that comes with tank and on following page.
Third, a dry contact is available on terminals H1 and H2 . It
operates similarly to D1-D2 above, but is only activated when
auxiliary heat is requested AND the compressor is off (i.e. when
the outdoor temperature has dropped below the selectable mini-
mum operating temperature). This should be used to actuate
very high temperature heating devices that would interfere with
heat pump operation if run simultaneously. HTS/CTS control
with tank sensor should be used. Like D1-D2, H1-H2 defaults
to ON .
D1-D2 and H1-H2 default to ON and so must be
used with an auxiliary heating device that has a
HIGH TEMPERATURE LIMITER to avoid a seri-
ous safety hazard.
If it is not desired to have D1-D2 default to ON when heat
pump is powered off, make the following wiring changes in the
heat pump’s electrical box, while referring to the Wiring/
Schematic diagram in the Model Specific Information chap-
ter.

Find the light brown wire connected between terminal strip
terminal D1 and the Elec. Aux. Relay . Move it from pin 5 to
pin 2 of the relay.

Find the purple wire connected between the left side of the
control board and the
Elec. Aux. Relay . Move if from termi-
nal L4 (NOT_HYD_AUX) to DO_2 (HYD_AUX) on the con-
trol board.
Now D1-D2 will work as before, but will default to OFF when
heat pump is off.
BACnet Connections
If using BACnet for external control of heating/cooling de-
mand and/or monitoring of status, use a shielded twisted pair to
the connector at the bottom left of control board. There is an
optional termination jumper located above the connector.
See the BACnet Interface section for details.
TABLE 7 - BACnet Connections
Line Description
A Communi
B Communication -
GND Ground
Use a shielded twisted pair cable.