Nordic ATWC Series, Installation And Service Manual, Page: 34 / 106

PRELIMINARY: 24-Sep-2021 Page 34 002536MAN-00
Outdoor Reset
As mentioned earlier, lower heating setpoints will translate directly into a higher COP (efficiency).
When Control Source HYD is set to Setpoints , an optional Outdoor Reset control algorithm is available for heating mode, which
reduces the heating temperature setpoints at warmer outdoor temperatures as measured by the outdoor unit. To enable it, simply
click on the Outdoor Reset button at the top of the Setpoint Control window. The button will change to say Enabled, the indicator will
come on and the Outdoor Reset Table will appear.
The table is created by subtracting the value of the Outdoor Reset Factor from the original setpoints once for each table row .
The user-selected Hot Setpoints are located in the top row(<5°F), and the next row down equals the row above minus the Outdoor
Reset Factor. The table row in use based on current outdoor temperature is shown in red.
It can be seen that as outdoor temperature rises and heating load falls, the heating mode buffer tank temperature will be de-
creased and a higher seasonal efficiency will result.
Setpoint Control Method 2 - Indoor Loop (ICR)
Two
Tanks
It is possible to use all of the Setpoint Control Method 1 settings, and operate two buffer tanks: one for heated water and one for
chilled water. The heat pump will switch over to cooling tank when it receives an external “ O ” signal, and this signal (along with C/
GND ) will also energize a 3-way valve to divert flow to the cold tank (see Piping section).
However, it is suggested to use Method 4 (External HTS/CTS with two tanks) for this purpose. This will require two external tank
temperature sensors, but has the benefit of both tank temperatures being constantly monitored and also has the added Auto Maintain
option (maintaining both hot and cold tank setpoints without the requirement for an external “ O ” signal).
RED—Heating
BLUE—Cooling
Click to enable Outdoor
Reset, or use LCD
Actual Setpoint
is reduced by
Outdoor Reset
Row in use will be RED
Outdoor Reset Factor
adjusts the tempera-
ture difference be-
tween table rows
Change units of
Setpoint Control only