Nordic ATWC Series, Installation And Service Manual, Page: 19 / 106

PRELIMINARY: 24-Sep-2021 Page 19 002536MAN-00
Piping
Indoor Loop Water Lines
The connections for the Indoor Loop circuit are 1” or
1-1/4” brass FNPT. They are labelled as INDOOR IN and
INDOOR OUT. The ports are located on the left side of the
unit near the back.
Recommended buffer tank piping is shown in diagrams on
following pages. They show all of the recommended compo-
nents as well as where they should be placed. If other types of
components are used or connected differently, this is done at
user’s discretion with the caution that heat pump may or may
not work properly.
Note there is a separate set of piping diagrams for
DHW heating heat pumps with the double wall condenser
option.
NOTE: It is recommended that the water lines between the
heat pump and the buffer tank be copper or other high tempera-
ture piping.
NOTE: Care should be taken when routing the water lines to
ensure that adequate access to the heat pump is maintained so
as to not compromise ease of serviceability.
The minimum buffer tank size should follow the rule of 8
US gallons per ton of heat pump capacity. The following table
shows the minimum buffer tank size for each heat pump along
with the recommended size. The recommended size will mini-
mize the number of starts per hour and provide longer runtimes
for improved efficiency.
TABLE 12 - Buffer Tank Size
Heat Pump Size
Minimum Size
gal (L)
Recommended Size
gal (L)
45 24 (90) 50 (190)
55 32 (120) 70 (265)
75 48 (180) 70 (265)
100 70 (265) 100 (380)
If a tank size is not available, use the next size larger tank.
65 40 (150) 70 (265)
80 52 (200) 70 (265)
Number of Tanks
All dedicated DHW heat pumps (with the double wall con-
denser option) require one DHW holding tank, equivalent in
function to the single buffer tank systems discussed below.
All space heating/cooling heat pumps with single wall con-
denser require at least one buffer tank . If there is one buffer
tank, it will contain the heated or chilled water. The water in the
tank will be chilled when the “ O” signal is activated. This buffer
tank may have electric elements for auxiliary heat, or an existing
boiler may be used. See piping diagrams on following pages.
If there is need for heating and cooling simultaneously or
in close proximity, or if need for a seasonal switchover is to be
avoided, two buffer tanks maybe installed. One will be always
be heated, and one will be always be chilled, controlled using
the on-board Setpoint Control routine. This routine has two op-
tions: the “ O ” signal from an external controller may be used to
tell the heat pump to switch to cooling mode and cool the cold
tank, or the “ Auto Maintain ” function may be used to automati-
cally maintain both the hot and cold tanks without external input.
See Operation section, and piping diagrams on following pages.
See the chapter One or Two Buffer Tanks? near the begin-
ning of this manual for a discussion of this topic.