Nordic W Series Manual

ISSUE 04: 23-Sep-2022 Page 1 002500MAN-01
Maritime Geothermal Ltd.
P.O. Box 2555, 170 Plantation Road
Petitcodiac, NB E4Z 6H4
[phone]
Water-to-Water Heat Pumps:
W-Series (Standard Range),
WH-Series (High Temperature),
WP-Series (Pool Heating)
Model Sizes 25-80 (Heating/Cooling)
Model Sizes 45-80 (Pool Heating)
Model Size 85 (Domestic Hot Water)
[e-mail]
www.nordicghp.com
002500MAN-01
ISSUE 04: 23-Sep-2022
W/WH-65/75/80
W/WH-25/45/55
WP-45/55/65/75/80
WH-85-H (DHW)
Application, Installation, & Service Manual

ISSUE 04: 23-Sep-2022 Page 2 002500MAN-01
WARNING: Ensure all access panels are in place and properly secured before applying power to the unit.
Failure to do so may cause electrical shock.
WARNING: Before performing service or maintenance on the heat pump system, ensure all power sources
are DISCONNECTED. Electrical shock can cause serious personal injury or death.
WARNING: Heat pump systems contain refrigerant under high pressure and as such can be hazardous to
work on. Only qualified service personnel should install, repair, or service the heat pump.
CAUTION: Safety glasses and work gloves should be worn at all times whenever a heat pump is serviced.
A fire extinguisher and proper ventilation should be present whenever brazing is performed.
CAUTION: Venting refrigerant to atmosphere is illegal. A proper refrigerant recovery system must be
employed whenever repairs require removal of refrigerant from the heat pump.
SAFETY PRECAUTIONS
Model Nomenclature
WH - 65 - HACW - B - 1S - CC - xx
Series:
W = standard temperature water to water
WH = high temperature water to water
WP = pool heating water to water
Nominal Size:
25 = 020/21 compressor
45 = 030/32 compressor
55 = 040/42 compressor
65 = 051/54 compressor
75 = 060/61 compressor
80 = 068/70 compressor
85 = 094 compressor
Functions:
H = heating
AC = active cooling
(reversing valve)
W = DHW desuperheater
Refrigerant:
P = R410a
B = R134a
Voltage Code:
1 = 208/230-1-60
2 = 208-3-60
3 = 265/277-1-60
4 = 460-3-60
5 = 575-3-60
6 = 220-1-50
7 = 380-3-50
Indoor Loop Exchanger:
C = copper coaxial
Y = CuNi coaxial & piping
Z = CuNi coaxial coil only
T = titanium/PVC coaxial
P = brazed plate
D = double wall brazed plate
Revision:
01, 02 etc.
Compressor:
T = 2-stage scroll
S = single stage scroll
Outdoor Loop Exchanger:
C = copper coaxial
Y = CuNi coil & piping
Z = CuNi coil only
P = brazed plate

ISSUE 04: 23-Sep-2022 Page 3 002500MAN-01
APPLICATION TABLE: W-SERIES
MODEL FUNCTION REFRIGERANT VOLTAGE COMPRESOR OUTDOOR
COIL
INDOOR
COIL REVISIONS
W-25 HACW P
1
2
4
6
7
T
C
Y
Z
C
Y
Z
11
W-45 HACW P
1
2
4
5
6
7
T
C
Y
Z
C
Y
Z
11
W-55 HACW P
1
2
4
5
6
7
T
C
Y
Z
C
Y
Z
11
W-65 HACW P
1
2
4
5
6
7
T
C
Y
Z
C
Y
Z
11
W-75 HACW P
1 T
C
Y
Z
C
Y
Z
11
2 T
4 T
5 T
6 S
7 T
W-80 HACW P
1
2
4
5
7
S
C
Y
Z
C
Y
Z
11
This manual applies only to the models and revisions listed in this table
APPLICATION TABLE - FIRMWARE AND PC APP
Firmware Version* Associated PC APP Version
MGT GEN2 Bootload Firmware V3.60+ MGT GEN2 PC APP V2.00+

ISSUE 04: 23-Sep-2022 Page 4 002500MAN-01
APPLICATION TABLE: WH-SERIES
SIZE FUNCTION REFRIGERANT VOLTAGE COMPRESSOR OUTDOOR
COIL
INDOOR
COIL REVISIONS
WH-25
H B
1
2
4
6
7
S
C
Y
Z
C
Y
Z
04
HACW B
1
2
4
6
7
S
C
Y
Z
C
Y
Z
02
WH-45
WH-55
WH-65
H B
1
2
4
5
6
7
S
C
Y
Z
C
Y
Z
04
HACW B
1
2
4
5
6
7
S
C
Y
Z
C
Y
Z
02
WH-75
H B
1
2
4
5
7
S
C
Y
Z
C
Y
Z
04
HACW B
1
2
4
5
7
S
C
Y
Z
C
Y
Z
02
WH-80
H B
1
2
4
5
6
7
S
C
Y
Z
C
Y
Z
04
HACW B
1
2
4
5
6
7
S
C
Y
Z
C
Y
Z
02
WH-85 H B
2
4
5
7
S P D 04
This manual applies only to the models and revisions listed in this table
Maritime Geothermal Ltd. has a continuous improvement policy and reserves the right to modify specification
data at any time without prior notice .
APPLICATION TABLE - FIRMWARE AND PC APP
Firmware Version* Associated PC APP Version
MGT GEN2 Bootload Firmware V3.60+ MGT GEN2 PC APP V2.00+

ISSUE 04: 23-Sep-2022 Page 5 002500MAN-01
APPLICATION TABLE: WP-SERIES
MODEL FUNCTION REFRIGERANT VOLTAGE COMPRESOR OUTDOOR
COIL
INDOOR
COIL REVISIONS
WP-45 H P
1
2
4
5
6
7
S
C
Y
Z
T 03
WP-55 H P
1
2
4
5
6
7
S
C
Y
Z
T 03
WP-65 H P
1
2
4
5
6
7
S
C
Y
Z
T 03
WP-75 H P
1
2
4
5
7
C
Y
Z
T 03
WP-80 H P
1
2
4
5
6
7
S
C
Y
Z
T 03
This manual applies only to the models and revisions listed in this table
S
APPLICATION TABLE - FIRMWARE AND PC APP
Firmware Version* Associated PC APP Version
MGT GEN2 Bootload Firmware V3.60+ MGT GEN2 PC APP V2.00+

ISSUE 04: 23-Sep-2022 Page 6 002500MAN-01
Table of Contents
Documents .......................................................................... 7
Tables ................................................................................... 8
Series System Description ............................................. 9
W-series .................................................................................. 9
WH-series ................................................................................ 9
WP-series ................................................................................ 9
One or Two Buffer Tanks? ............................................ 10
Single Buffer Tank Systems .................................................. 10
Dual Buffer Tank Systems .................................................... 10
Sizing for Space Heating/Cooling ................................ 11
W/WH-Series Heat Pump Sizing .......................................... 11
Auxiliary Heat Sizing ............................................................. 11
Sizing for Pool Heating ................................................... 12
Indoor Pools .......................................................................... 12
Outdoor Pools / Hot Tubs ...................................................... 12
Outdoor Pools / Hot Tub Heat Load ....................................... 12
WP-Series Heat Pump Sizing ............................................... 12
Installation Basics ........................................................... 13
Unpacking the unit ................................................................ 13
Unit Placement ..................................................................... 13
Sample Bill of Materials - W/WH Series on Ground Loop ...... 13
Sample Bill of Materials - W/WH Series on Open Loop ........ 13
Wiring ................................................................................. 14
Power Supply Connections ................................................... 14
Indoor Circulator Pump Wiring .............................................. 14
Outdoor Loop Pump Module Wiring (Ground Loop Only) ..... 14
Control Transformer .............................................................. 14
Open/Closed Loop Wiring ..................................................... 14
Domestic Hot Water (Desuperheater) ................................... 14
BACnet Connections ............................................................. 15
Setpoint Control Connections ................................................ 15
Setpoint Control: Aux. Connections ....................................... 15
Aquastat Connections (Optional) .......................................... 15
Disable Switch (field installed) ............................................... 15
Summer Setback Switch (field installed) ................................ 15
Other Connections ................................................................. 15
002241CDG - Typ. GEN2 Aux. Heat & Circulator Wiring ...... 16
002375QSS - AltSource Tanks: Getting Started ................... 17
002067CDG - Typ. Heating Only Zone Wiring (Setpoint) ...... 18
002068CDG - Typ. Htg/Cooling Zone Wiring (Setpoint) ........ 19
002069CDG - Typ. Heating Only Zone Wiring (Signals) ........ 20
002070CDG - Typ. Htg/Cooling Zone Wiring (Signals) .......... 21
Piping ................................................................................. 22
W/WH-Series: Number of Tanks ........................................... 22
Indoor Loop & Buffer Tank ..................................................... 22
Outdoor Loop ........................................................................ 22
Domestic Hot Water (Desuperheater) Connections .............. 22
WH-HAC: Modulating Water Valve ....................................... 23
WP-Series Pool Piping Connections ..................................... 23
002287PDG - Typical Piping Connections - W/WH 25-80 ..... 24
002366PDG - Recommended Buffer Tank Piping ................. 25
002367PDG - Auxiliary Boiler Piping ..................................... 26
002528PDG - Buffer Tank Piping - Multiple Units .................. 27
002240PDG - DHW with Single Wall Condenser ................... 28
002545PDG - Tank Piping for Direct DHW Heating ............... 29
002252PDG - Two Tank Piping with a Rev. Heat Pump ........ 30
002527PDG - 2 Tank Piping w/Multiple Rev. Heat Pumps .... 31
002288PDG - Two Tank Simultaneous Heating/Cooling ....... 32
001680PDG - Two Tank Simultaneous (Diverting) ................ 33
000530PDG - Typical Zone Types ......................................... 34
002286PDG - Snow Melt w/Ground Loop Re-heating ........... 35
000970PDG - Desup. Connection to DHW Pre-Heat Tank .... 36
002384PDG - Desup. Connection - Multiple Units ................. 37
Ground Loop Installations ............................................ 38
Circulator Pump Module ....................................................... 38
Flushing & Purging ............................................................... 38
Antifreeze Solution ................................................................ 39
Initial Pressurization .............................................................. 39
Pipe Insulation ...................................................................... 39
000608INF - Typical Horiz. Ground Loop Configuration ........ 40
000609INF - Typical Vert. Ground Loop Configuration .......... 41
000906CDG - Circulator Pump Module Installation .............. 42
001823CDG - Dual Flow Pump Module Installation ............... 43
000629PDG - Pump Module Inst - 2 Units on 1 Loop ........... 44
Open Loop Installations ................................................ 45
Well Water Temperature ....................................................... 45
Well Water Flow .................................................................... 45
Well Water Quality ................................................................ 45
Water Discharge Methods .................................................... 45
Water Valve .......................................................................... 46
Water Flow Control ............................................................... 47
Submersible Pump Selection ................................................ 47
Submersible Pump Power Draw ............................................ 47
Plumbing the Heat Pump ...................................................... 47
Pipe Insulation ...................................................................... 47
000907CDG - Typical Open Loop Installation ....................... 48
001822CDG - Dual Flow Open Loop Installation .................. 49
000619INF - Ground Water Disposal Methods ..................... 50
Operation ........................................................................... 51
1. BACnet Control ................................................................. 51
2. Signals / Hardwired Control .............................................. 51
3. Setpoint Control ................................................................ 51
Setpoint Control Method 1 - Indoor Loop (ICR), One Tank .... 51
Typical Temperature Setpoints ........................................... 52
Summer Setback ................................................................ 52
Outdoor Reset .................................................................... 53
Setpoint Control Method 2 - Indoor Loop (ICR), 2 Tanks ....... 54
Setpoint Control Method 3 - External HTS/CTS, One Tank .. 55
a) Heat Pump Mode ........................................................... 55
b) Chiller Mode ................................................................... 56
Setpoint Control Method 4 - External HTS/CTS, 2 Tanks ..... 57
PC Application (PC App) ............................................... 58
LCD Interface & Menus .................................................. 70
BACnet Interface .............................................................. 72
Startup Procedure ........................................................... 76
Startup Record ...................................................................... 78
Routine Maintenance ...................................................... 79
Troubleshooting Guide .................................................. 80
Repair Procedures .......................................................... 90
Pumpdown Procedure .......................................................... 90
General Repair Procedure .................................................... 90
Vacuuming & Charging Procedure ....................................... 90
Compressor Replacement Procedure ................................... 91
Control Board Replacement Procedure ................................ 92
LCD Interface (Display) Board Replacement Procedure ....... 93
Model Specific Information: W-Series ....................... 94
W-Series Refrigerant Charge ................................................ 94
W-Series Shipping Information ............................................. 94
W-Series Operating Temperature Limits ............................... 94
W-Series Required Indoor & Outdoor Loop Flow Rates ....... 94
W-Series Sound Levels (dBA) .............................................. 94
W-Series Pressure Drop Data ............................................... 95
W-Series: Standard Capacity Ratings - Closed Loop ............ 97
W-Series: Standard Capacity Ratings - Open Loop ............... 98

ISSUE 04: 23-Sep-2022 Page 7 002500MAN-01
Performance Tables: W-25 .................................................... 99
Performance Tables: W-45 .................................................. 100
Performance Tables: W-55 .................................................. 101
Performance Tables: W-65 .................................................. 102
Performance Tables: W-75 .................................................. 103
Performance Tables: W-80 .................................................. 104
W-Series Electrical Specifications ...................................... 105
W-Series Dimensions ......................................................... 106
Model Specific Information: WH-Series ................... 107
WH-Series Refrigerant Charge ........................................... 107
WH-Series Shipping Information ......................................... 107
WH-Series Operating Temperature Limits .......................... 107
WH-Series Required Indoor & Outdoor Loop Flow Rates ... 107
WH-Series Sound Levels (dBA) .......................................... 107
WH-Series Pressure Drop Data ........................................... 108
Performance Tables: WH-25 ............................................... 110
Performance Tables: WH-45 ............................................... 111
Performance Tables: WH-55 ............................................... 112
Performance Tables: WH-65 ............................................... 113
Performance Tables: WH-75 ............................................... 114
Performance Tables: WH-80 ............................................... 115
Performance Tables: WH-85 ............................................... 116
WH-Series Electrical Specifications .................................... 117
WH-Series Dimensions ....................................................... 118
Model Specific Information: WP-Series ................... 119
WP-Series Refrigerant Charge ........................................... 119
WP-Series Shipping Information ......................................... 119
WP-Series Operating Temperature Limits .......................... 119
WP-Series Required Loop Flow Rates ............................... 119
WP-Series Sound Levels (dBA) .......................................... 119
WP-Series Pool Water Pressure Drop ................................. 119
WP-Series Outdoor Loop Water Pressure Drop .................. 120
WP-Series Capacity Ratings ............................................... 121
WP-Series Electrical Specifications .................................... 122
WP-Series Dimensions ....................................................... 122
W/WH/WP Wiring Diagrams & Electrical Box Layouts .. 123
Refrigeration Circuit Diagrams ........................................ 135
Appendix A: Control Board Description ................... 138
Appendix B: USB Driver Installation ........................ 142
Appendix C: PC App Installation .............................. 143
Appendix D: Updating Firmware ................................ 144
Warranty ........................................................................... 147
002241CDG - Typical GEN2 Auxiliary Heat & Circulator Wiring ............................................................ 16
002375QSS - AltSource Tanks: Getting Started .................................................................................... 17
002067CDG - Typical Zone and Auxiliary Wiring with GEN2 Setpoint Control (Heating Only) .............. 18
002068CDG - Typical Zone and Auxiliary Wiring with GEN2 Setpoint Control (Heating & Cooling) ...... 19
002069CDG - Typical Zone and Auxiliary Wiring with GEN2 Hardwired Option (Heating Only) ............ 20
002070CDG - Typical Zone and Auxiliary Wiring with GEN2 Hardwired Option (Heating & Cooling) .... 21
002287PDG - Typical Piping Connections - W/WH 25-80 ..................................................................... 24
002366PDG - Recommended Hydronic Buffer Tank Piping .................................................................. 25
002367PDG - Auxiliary Boiler Piping ..................................................................................................... 26
002528PDG - Buffer Tank Piping - Multiple Units .................................................................................. 27
002240PDG - High Temperature Single Wall Unit Connection to DHW Tank ........................................ 28
002545PDG - Tank Piping for Direct DHW Heating for Heat Pumps with Double Wall Condenser ........ 29
002252PDG - Two Tank Piping with a Reversing Heat Pump ............................................................... 30
002527PDG - Two Tank Piping with Multiple Reversing Heat Pumps .................................................... 31
002288PDG - Two Tank Simultaneous Heating / Cooling ..................................................................... 32
001680PDG - Two Tank Simultaneous Heating / Cooling (Diverting Arrangement) ............................... 33
000530PDG - Typical Zone Types for Hydronic Applications ................................................................. 34
002286PDG - Geothermal Snow Melt System with Warm-Weather Ground Loop Re-heating ............... 35
000970PDG - Desuperheater Connection to DHW Pre-Heat Tank ....................................................... 36
002384PDG - Desuperheater Connection to DHW Pre-Heat Tank - Multiple Units ............................... 37
000608INF - Typical Horizontal Ground Loop Configuration .................................................................. 40
000609INF - Typical Vertical Ground Loop Configuration ....................................................................... 41
000906CDG - Geo-Flo Circulator Pump Module Installation ................................................................. 42
001823CDG - Dual Flow Circulator Pump Module Installation for 2-Stage Heat Pumps ........................ 43
000629PDG - Circulator Pump Module Installation - Two Units on One Ground Loop ........................... 44
000907CDG - Typical Ground Water (Open Loop) Installation .............................................................. 48
001822CDG - Dual Flow Groundwater (Open Loop) Installation for 2-Stage Heat Pumps .................... 49
000619INF - Ground Water Disposal Methods ...................................................................................... 50
001889SCH - W/WH/WP-**-H***-*-1*-** Schematic Diagram ............................................................... 123
001890ELB - W/WH/WP-**-H***-*-1*-** Electrical Box Diagram ........................................................... 124
001934SCH - W/WH/WP-**-H***-*-2*-** Schematic Diagram ............................................................... 125
001935ELB - W/WH/WP-**-H***-*-2*-** Electrical Box Diagram ........................................................... 126
001936SCH - W/WH/WP-**-H***-*-4*-** Schematic Diagram ............................................................... 127
001937ELB - W/WH/WP-**-H***-*-4*-** Electrical Box Diagram ........................................................... 128
001938SCH - W/WH/WP-**-H***-*-5*-** Schematic Diagram ............................................................... 129
001939ELB - W/WH/WP-**-H***-*-5*-** Electrical Box Diagram ........................................................... 130
001940SCH - W/WH/WP-**-H***-*-6*-** Schematic Diagram ............................................................... 131
001941ELB - W/WH/WP-**-H***-*-6*-** Electrical Box Diagram ........................................................... 132
001942SCH - W/WH/WP-**-H***-*-7*-** Schematic Diagram ............................................................... 133
001943ELB - W/WH/WP-**-H***-*-7*-** Electrical Box Diagram ........................................................... 134
002398RCD - W/WH-HACW Refrigeration Circuit Diagram (Reversing, with Desuperheater) ............. 135
001877RCD - W/WH/WP-H Refrigeration Circuit Diagram (Non-Reversing) ........................................ 136
001674RCD - WH-85 Domestic Hot Water Heating Refrigeration Circuit Diagram ............................. 137
Documents

ISSUE 04: 23-Sep-2022 Page 8 002500MAN-01
Tables
Table 1 - Heat Pump Size vs. Heated Area ........................................................................................... 11
Table 2 - Heat Pump Size vs. Heated Area ........................................................................................... 11
Table 3 - Auxiliary Heat Sizing ............................................................................................................... 11
Table 4 - Power Supply Connections ..................................................................................................... 14
Table 5 - Indoor & Outdoor Circulator Connections ............................................................................... 14
Table 6 - BACnet Connections .............................................................................................................. 15
Table 7 - Setpoint Control Connections ................................................................................................. 15
Table 8 - Setpoint Control: Aux. Connections ........................................................................................ 15
Table 9 - Aquastat (Signals Control) Connections ................................................................................. 15
Table 10 - Buffer Tank Size ................................................................................................................... 22
Table 11 - Antifreeze Percentages ........................................................................................................ 39
Table 12 - Volume of Fluid per 100 ft of Pipe ......................................................................................... 39
Table 13 - Required Flow (Open Loop) .................................................................................................. 45
Table 14 - W-Series Typical Temperature Setpoints ............................................................................. 52
Table 15 - WP-Series Typical Temperature Setpoints ........................................................................... 52
Table 16 - WH-Series Typical Temperature Setpoints ........................................................................... 52
Table 17 - Typical Temperature Setpoints (HTS/CTS Method - Chiller Mode) ....................................... 56
Table 18 - BACnet Objects - Control Signals (Read/Write) ..................................................................... 72
Table 19 - BACnet Objects - Operation Mode Description (Read Only) ................................................. 72
Table 20 - BACnet Objects - Limits Description (Read Only) .................................................................. 72
Table 21 - BACnet Objects - Data (Read Only) ...................................................................................... 73
Table 22 - BACnet Objects - Alarm Descriptions (Read Only) ................................................................ 74
Table 23 - BACnet Objects - Fault Descriptions (Read Only) ................................................................. 75
Table 24 - W-Series Refrigerant Charge ................................................................................................ 94
Table 25 - W-Series Shipping Information ............................................................................................. 94
Table 26 - W-Series Operating Temperature Limits .............................................................................. 94
Table 27 - W-Series Required Indoor & Outdoor Loop Flow Rates ....................................................... 94
Table 28 - W-Series Sound Levels (dBA) .............................................................................................. 94
Table 29 - W-Series Pressure Drop Data .............................................................................................. 95
Table 30 - W-Series Standard Capacity Ratings - Ground Loop Heating 60Hz ..................................... 97
Table 31 - W-Series Standard Capacity Ratings - Ground Loop Cooling 60Hz ..................................... 97
Table 32 - W-Series Standard Capacity Ratings - Ground Water Heating 60Hz ................................... 98
Table 33 - W-Series Standard Capacity Ratings - Ground Water Cooling 60Hz ................................... 98
Table 34 - W-Series Electrical Specifications ...................................................................................... 105
Table 35 - WH-Series Refrigerant Charge ........................................................................................... 107
Table 36 - WH-Series Shipping Information ......................................................................................... 107
Table 37 - WH-Series Operating Temperature Limits .......................................................................... 107
Table 38 - WH-Series Required Indoor & Outdoor Loop Flow Rates ................................................... 107
Table 39 - WH-Series Sound Levels (dBA) .......................................................................................... 107
Table 40 - WH-Series Pressure Drop Data .......................................................................................... 108
Table 41 - WH-Series Electrical Specifications .................................................................................... 117
Table 42 - WP-Series Refrigerant Charge ........................................................................................... 119
Table 43 - WP-Series Shipping Information ......................................................................................... 119
Table 44 - WP-Series Operating Temperature Limits .......................................................................... 119
Table 45 - WP-Series Required Indoor & Outdoor Loop Flow Rates ................................................... 119
Table 46 - WP-Series Sound Levels (dBA) .......................................................................................... 119
Table 47 - WP-Series Pool Water Pressure Drop ................................................................................ 119
Table 48 - WP-Series Outdoor Loop Pressure Drop ............................................................................ 120
Table 49 - WP-Series Capacity Ratings................................................................................................ 121
Table 50 - WP-Series Electrical Specifications .................................................................................... 122
Table A1 - Control Board Connector Descriptions (Top)....................................................................... 139
Table A2 - Control Board Connector Descriptions (Left Side) ............................................................. 139
Table A3 - Control Board Connector Descriptions (Bottom) ................................................................ 140
Table A4 - Control Board Connector Descriptions (Right Side) ........................................................... 141

ISSUE 04: 23-Sep-2022 Page 9 002500MAN-01
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Sep
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9
002500MAN
Series Description
Maritime Geothermal Ltd. has made NORDIC brand pack-
age water-to-water heat pumps in residential sizes (nominal 2 to
6 tons) for almost 40 years. They are used for residential heat-
ing through hydronic distribution systems like radiant in-floor
piping, radiant ceiling panels, radiators, hydronic baseboards, or
hydronic air handlers/fan coils. Reversing units (-HAC/HACW)
can also chill water for hydronic cooling applications.
Being a water source, ’geoexchange’, or ‘geothermal’ heat
pumps, these types of heat pumps do require a heat source in
heating mode, or a place to reject heat in cooling mode. This
can be:
a) a closed ground loop with a circulating water/
antifreeze solution; or
b) an open loop water well, with water re-injected in a
second well or otherwise run off.
1. Heating Mode
In heating mode, the heat pump heats water in a buffer
tank (or swimming pool) to a user-adjustable setpoint tempera-
ture, while extracting heat from the outdoor loop. If a closed
ground loop is used, the pumps are powered and controlled by
the heat pump; if open loop, a water valve is opened by the heat
pump during heating operation and closed when the heat pump
is idle.
Hydronic heating systems are easily zoned, and zones
may be in-floor heating, hydronic air handlers, or other hydronic
devices suitable for the water temperature capability of the heat
pump series. When a zone requires heat, its zone thermostat
calls for a zone circulator pump or zone valve to activate, so that
hot water from the buffer tank is sent to the zone requiring heat.
Note that there is no direct connection between the zone ther-
mostat and the heat pump, the functions of each being separat-
ed by the buffer tank.
2. Cooling Mode (Reversing models HACW/HAC only)
In cooling mode, the heat pump cools water in the buffer
tank. Heat is rejected to the outdoor loop.
Hydronic cooling is usually done through hydronic air han-
dlers, which have condensate drains to remove water that is
removed while dehumidifying the air. In less humid climates, in-
floor or radiant ceiling cooling is sometimes performed; such
systems can’t remove humidity from the air. In this case, care
must be taken to ensure the cooling surface does not fall below
the dew point temperature in order to prevent condensation on
floor surfaces.
There are several types of NORDIC water to water heat pumps:
W-series
This is the standard temperature geothermal space heat-
ing/cooling series, using R410a refrigerant. They can extract
heat from cold northern ground loops, and heat water on the
indoor side up to 120°F (49°C), using a dual-capacity (2-stage)
compressor.
WH-series
The WH-series is a high-temperature-range version of the
W-series, using R134a refrigerant. They can heat water on the
indoor side up to 160°F (71°C), but require a minimum heat
source fluid temperature 45°F (7°C).
For both W and WH series, the indoor and outdoor loop
heat exchangers are heavy duty coaxial copper / steel models
with optional CuNi inner tube. Scroll compressors and Electron-
ic Expansion Valves (EEVs) are standard. The electronic con-
trol board has full hydronic temperature control, laptop connec-
tivity via USB with free PC App, LCD interface, electronic
readout of all pressures and temperatures, data logging & gra-
phing, and BACnet.
The Nordic WH-85-H is a special purpose model with a
brazed plate evaporator and double wall brazed plate conden-
ser for direct domestic hot water heating in commercial applica-
tions. (Other W/WH model sizes may be used for DHW heating
or pre-heating, but normally must be used with a secondary
heat exchanger or indirect tank with coil to satisfy codes.)
WP-series
This is the dedicated pool heating version of the standard
temperature R410a W-series. Normally used for outdoor pools,
it has a titanium/PVC indoor loop coil, single stage compressor,
and no reversing valve. It can heat pool water to as high as
105°F (41°C), which is a suitable temperature for a hot tub or
spa.
* See Piping chapter for
an annotated copy of
this diagram

ISSUE 04: 23-Sep-2022 Page 10 002500MAN-01
One or Two Buffer Tanks?
Single Buffer Tank Systems
By far, this is how most systems are config-
ured. The heat pump either heats water in the
buffer tank for zone use during heating season, or
chills water in the buffer tank for zone use during
cooling season. Note that a single tank is always
all that is required for heating-only systems that
don’t do cooling.
Advantages Drawbacks
Simplest piping and control. Seasonal switchover from heating to cooling required, either
automatically through a zone controller or via a manual switch.
Takes the least amount of mechanical room space.
Lower equipment cost than a 2-tank system.
Works well for heating and cooling using 2-pipe air handlers
(and in-floor heating).
Dedicated domestic hot water preheating is not possible in sum-
mer due to no hot tank being available.
Is the go-to option for heating-only systems. Simultaneous heating and cooling is not possible; heating and
cooling in close proximity is not practical.
Dual Buffer Tank Systems
There are some situations in which it
is advantageous to use two tanks, one
always heated and one always chilled.
The heat pump has a built in routine to
automatically maintain both the hot and
cold tank temperatures.
In this system, hot and cold water
are available for use at any time. In the
setup described here, the heat pump
switches back and forth using a 3-way
valve to heat one tank or cool the other.
(With a water to water heat pump, it is also
possible to pump heat from one tank to the
other for true “simultaneous” heating and
cooling, although such a system is more
complex to install.)
Advantages Drawbacks
No seasonal switchover is required. Heating and cooling distribution devices need to be separate
devices or flow directed with the addition of zone 3-way valves.
Works well for heating and cooling using 4-pipe air handlers(and
in-floor heating). Takes more mechanical room space.
Higher equipment cost than a 1-tank system.
Year-round dedicated domestic hot water preheating is possible. Plumbing and control may get complicated if using a standalone
heating device (like a boiler) for auxiliary heat.
Simultaneous heating and cooling is possible; heating and cool-
ing in close proximity is practical
Plumbing and control may get complicated for multiple heat
pumps connected to same buffer tanks.
This is an important design choice that needs to be made when planning an installation. These systems are described more
fully in the following chapters.

ISSUE 04: 23-Sep-2022 Page 11 002500MAN-01
W/WH-Series Heat Pump Sizing
Table 1 shows the above grade size of building that can
typically be heated/cooled in northern climates for:
· W-series on a closed ground loop
· WH-series when indoor loop is normally being heated to
near its maximum temperature (160°F / 71°C).
TABLE 1 - Heat Pump Size vs. Heated Area
Model ft2 m2
W/WH-25 800 75
W/WH-55 2000 185
W/WH-65 2600 240
W/WH-75 3100 290
W/WH-80 3500 325
W/WH-45 1400 130
Table 2 shows the above grade size of building that can
typically be heated/cooled in northern climates for:
· W-series on an open loop (well water)
· WH-series when indoor loop is normally being heated to a
more moderate temperature (~130°F / 54°C).
TABLE 2 - Heat Pump Size vs. Heated Area
Model ft2 m2
W/WH-25 1000 95
W/WH-55 2500 230
W/WH-65 3200 295
W/WH-75 3800 355
W/WH-80 4200 390
W/WH-45 1800 165
THE TABLES ABOVE ARE FOR ESTIMATION ONLY.
THEY SHOULD NOT BE USED TO SELECT A FINAL UNIT
SIZE. They simply show what size unit is required for a north-
ern home with typical construction: R20 walls, R40 ceiling, and
average size and number of windows. The heated area is the
area of the above grade main level; the tables account for a
basement the same size as the heated area.
MARITME GEOTHERMAL LTD. HIGHLY RECOM-
MENDS THAT A PROPER HEAT LOSS/GAIN ANALYSIS BE
PERFORMED BY A PROFESSIONAL WITH APPROVED CSA
F-280 SOFTWARE BEFORE SELECTING THE HEAT PUMP
SIZE. For heating dominant climates, we recommend sizing
the unit to 100% of the heating design load for maximum
long term efficiency with minimal supplementary heat. The
unit should be installed as per CSA standard 448.2-02. For
ground loop applications, the ground loop should be de-
signed using suitable software with a multi-year analysis.
The analysis will result in a heat load for the coldest day,
which is influenced by, for example, the number of levels, the
size of the windows, the orientation of the home, attached gar-
age, bonus rooms, walk-in basement, and coldest outdoor tem-
perature for the region.
A heat pump model size can then be selected by compar-
ing the calculated heat load to the heat pump capacity at the
design indoor loop temperature, which can be found in the per-
formance tables in the Model Specific Information section.
For W-series, the Standard Capacity Ratings rather than de-
tailed performance tables can be used for simplicity. For 100%
heat pump sizing, choose a heat pump with a standard capacity
rating that matches or just slightly exceeds the calculated heat
load.
Some background on Standard Capacity Ratings: closed
ground loops are normally designed to reach a minimum tem-
perature of just below freezing at the end of the heating season,
in order to take advantage of the latent heat of groundwater (at
least in northern climates). Hence, the Standard Capacity Rat-
ings for Ground Loop Heating should apply in all northern cli-
mates. Conversely, the Standard Capacity Ratings for Ground
Water (open loop) heat pumps assume a well water temperature
of 50°F (10° C). In more southerly climates, the groundwater or
ground loop will probably be at a warmer minimum temperature,
and it will be necessary to consult the more detailed perfor-
mance tables for heat pump output at a different ELT.
In cooling dominant climates, the heat pump should be
similarly sized using the Ground Loop Cooling or Ground Water
Cooling Standard Capacity Ratings. Even in northern heating
dominant climates, it should be ensured that 100% of the
cooling load will be covered when sizing the heat pump,
since there is normally no auxiliary or backup cooling avail-
able.
Auxiliary Heat Sizing
The easiest way to provide auxiliary or backup heat for
new installations is by installing a buffer tank that has electric
elements. Buffer tanks with elements that are certified for space
heating use are available as accessories from Maritime Geo-
thermal Ltd., or others may be used. For retrofits, often an ex-
isting heat device can be used for auxiliary heat. Note that if the
geothermal heat pump is sized for 100% of the coldest day heat
load, auxiliary heat is not strictly required (unlike with an air
source heat pump).
For full backup, an option which is good for peace of mind
(should the heat pump experience a problem) but can require
significant electrical service capacity, an element size can be
chosen that covers 100% of the coldest day heat load, accord-
ing to the heat loss analysis mentioned in the last section. If a
heat loss analysis is not available, the following table may be
used as a guide.
TABLE 3 - Auxiliary Heat Sizing
Model Size
Tank Element Size
Recommended EcoUltra Tank Available
25 7 kW 12 kW (50 gal)
45 10 kW 12 kW (50 gal)
55 12 kW 15 kW (70 gal)
65 15 kW 15 kW (70 gal)
75 20 kW 20 kW (70 gal)
80 20 kW 20 kW (70 gal)
For heat pumps that are sized to cover less than 100% of
the coldest day heat load, the elements can be sized to make up
the coldest-day difference. The CSA installation standard al-
lows geothermal heat pumps to be sized to as little as 75% of
the coldest day heat load.
For retrofits, the existing heating device (e.g. an electric or
gas boiler) may be used for auxiliary heat. It should be wired as
described in the Wiring section, and piped in a parallel arrange-
ment as per the diagram in the Piping section.
Sizing for Space Heating/Cooling

ISSUE 04: 23-Sep-2022 Page 12 002500MAN-01
Indoor Pools
While both indoor and outdoor pools normally need to be
heated, indoor pools have the additional consideration of requir-
ing dehumidification of the pool room air, to avoid moisture dam-
age to the building envelope.
A NORDIC PC-series indoor pool room dehumidifier re-
jects its heat into the pool room air or pool water, and can pro-
vide all the heat needed for the water in a typical indoor pool
while dehumidifying. Because it fulfills both purposes, it is the
preferred way to heat indoor pools. It is sized according to the
surface area of the indoor pool; see the PC-series manual for
detailed sizing method.
Outdoor Pools / Hot Tubs
On the other hand, outdoor pools or hot tubs have no air
dehumidification requirement. They may be economically heat-
ed by a water source heat pump, which may be:
a) A dedicated WP-series heat pump, which directly heats
pool water circulated by the pool filter pump through its tita-
nium/PVC heat exchanger; and extracts its heat from a
closed ground loop / open loop water well that may or may
not be shared with a heat pump that heats or cools the
house.
b) A heating zone from a zoned hydronic heating system in
the house, using a hydronic water to pool water heat ex-
changer.
Sizing for Pool Heating
Outdoor Pool/Hot Tub Heat Load
The heat load from an outdoor pool or hot tub is influenced
by many factors:
· Difference between desired pool temperature and outdoor
temperature during coldest month of use
· Wind exposure
· Humidity
· Covered vs. not covered
To calculate an approximate heat load for an outdoor
swimming pool or spa, follow these steps:
1. Determine your desired swimming pool or hot tub tempera-
ture in °F. Pools are often kept at 80°F (27°C) and hot
tubs are often kept at 104°F (40°C).
2. Determine the average outdoor temperature in °F for the
coldest month of pool use.
3. Subtract the average temperature for the coldest month
from the desired pool temperature. This will give you
the Temperature Rise needed in °F.
4. Calculate the Pool Surface Area in square feet.
5. Use the following formula to determine the pool heat load
in Btu/hr:
Pool Surface Area x Temperature Rise x 12
This formula is based on a 1° to 1.25ºF temperature rise
per hour and a 3.5 mph (5.5 km/h) average wind at the pool
surface. Temperature rise is a function of the heat pump’s out-
put and depth of the pool, or how much water is in it; this can be
checked after a model size is selected, below. For a 1.5ºF rise
multiply by 1.5. For a 2ºF rise multiply by 2.0.
WP-Series Heat Pump Sizing
Once you have determined the pool’s heat load, you can
match it to a WP-Series model size in the Capacity Ratings
table in the Model Specific Information: WP-Series section.
The table shows the heating capacity at two water tempera-
tures: 80°F (27°C) for a pool, and 104°F (40°C) for a hot tub.
The table also lists two ground loop temperatures; normally in
the summer (when heat is being rejected into a shared ground
loop due to air conditioning) the higher of the two (50°F / 10°C)
can be counted on, regardless of whether an open or closed
loop is used.
Note that heat load from an outdoor pool can be very high,
and even the largest model size WP-80 might not meet the heat
load. In this case, an auxiliary heater could be considered; or
another approach would be to expect the pool to be cooler than
the setpoint temperature during colder weather. The heating
shortfall on colder days can be mitigated through consistent use
of an insulated pool cover.
Note that any water to water heat pump is designed to be
installed in an indoor mechanical room, rather than outdoors
near the pool like an air source pool heat pump.

ISSUE 04: 23-Sep-2022 Page 13 002500MAN-01
Installation Basics
Unpacking the Unit
When the heat pump reaches its destination it should be
unpacked to determine if any damage has occurred during
shipment. Any visible damage should be noted on the carrier's
freight bill and a claim filed.
Unit Placement
The placement of a hydronic heat pump has negligible
effects on the efficiency and operation of the system. The buffer
tank should be placed next to the heat pump. For open loop
systems, the unit can be placed near the well water system.
Ground loop system units can be placed near where the ground
loop pipes enter the structure to keep the ground loop piping,
heat pump and circulator pump module in one location. The
hydronic layout may make a particular location ideal for the unit
installation.
Looking at the side of the heat pump where the pipes
come out, the front and right side access panels should remain
clear of obstruction for a distance of 2 feet to facilitate servicing.
Two units may be stacked, with a continuous rubber pad (not
just point supports) or pink/blue styrofoam between them.
It is recommended that the heat pump be placed on a
piece of 2'' Styrofoam, or the rubber pad available as an acces-
sory from Maritime Geothermal. This will deaden compressor
noise emitted from the bottom of the cabinet, and prevent cabi-
net corrosion.
Sample Bill of Materials -
W/WH Series on Ground Loop
FROM MARITIME GEOTHERMAL
• W/WH SERIES HEAT PUMP
• BUFFER TANK W/ELEMENTS __kW
(or INDIRECT TANK FOR DEDICATED DHW)
• P/T PORTS AND HOSE ADAPTERS (2)
• 1 OR 2 PUMP PACK
• PIPE ADAPTERS FOR PUMP PACK
OPTIONAL FROM MARITIME GEOTHERMAL
• ANTI-VIBRATION PAD
• SOUND JACKET
• SECURE START
• AHW-65 AIR HANDLER(S)
• MODULATING WATER VALVE FOR OUTDOOR LOOP
DHW
• PREHEAT TANK, 40 OR 60 GAL
• ½” COPPER PIPE
• ½” FITTINGS, BALL VALVES, BOILER DRAINS, CV
GROUND LOOP
• ¾” PE PIPE
• 1-1/4” PE PIPE
• PE PIPE FITTINGS
• 1” CLEAR HOSE (HEAT PUMP TO PUMP PACK)
• HOSE CLAMPS
• ANTIFREEZE: METHANOL OR PROP. GLYCOL
ZONES
• CIRCULATOR: HEAT PUMP TO TANK
• 1” PIPE & FITTINGS: HEAT PUMP TO TANK
• ZONES CIRCULATOR(S)
• ZONE TRANSFORMER & CIRC CONTACTOR
• ZONE VALVES (IF NOT INDIVIDUAL PUMPS)
• IN-FLOOR PIPING
• OTHER AIR HANDLERS, DUCTING
• ZONE THERMOSTATS
• ZONE SUPPLY & RETURN HEADERS
• PIPE & FITTINGS TO ZONES
• EXPANSION TANK
ELECTRICAL
• HEAT PUMP SERVICE WIRE 6-3 OR 8-3
• BUFFER TANK ELEMENT SERVICE WIRE
• HEAT PUMP BREAKER
• BUFFER TANK ELEMENT BREAKER
• ELEMENT CONTACTOR & ELEC. BOX (IF NOT WITH TANK)
• THERMOSTAT WIRE 18-4
• THERMOSTAT WIRE 18-2
• FORK TERMINALS FOR TSTAT WIRE (6)
• 2” STYROFOAM INSUL. (IF PAD NOT PURCHASED)
Sample Bill of Materials -
W/WH Series on Open Loop
FROM MARITIME GEOTHERMAL
• W/WH SERIES HEAT PUMP
• BUFFER TANK W/ELEMENTS __kW
(or INDIRECT TANK FOR DEDICATED DHW)
• P/T PORTS AND HOSE ADAPTERS (2)
• DOLE VALVE
• MOTORIZED WATER VALVE
OPTIONAL FROM MARITIME GEOTHERMAL
• ANTI-VIBRATION PAD
• SOUND JACKET
• SECURE START
• AHW-65 AIR HANDLER(S)
DHW
• PREHEAT TANK, 40 OR 60 GAL
• ½” COPPER PIPE
• ½” FITTINGS, BALL VALVES, BOILER DRAINS, CV
WATER SYSTEM
• 1” BLACK PLASTIC WATER PIPE
• 1” BARBED FITTINGS & HOSE CLAMPS
• SUBMERSIBLE PUMP (IF NOT EXISTING)
• PRESSURE TANK (IF NOT EXISTING)
• CYCLE STOP VALVE (OPTIONAL)
ZONES
• CIRCULATOR: HEAT PUMP TO TANK
• 1” PIPE & FITTINGS: HEAT PUMP TO TANK
• ZONES CIRCULATOR(S)
• ZONE TRANSFORMER & CIRC CONTACTOR
• ZONE VALVES (IF NOT INDIVIDUAL PUMPS)
• IN-FLOOR PIPING
• OTHER AIR HANDLERS, DUCTING
• ZONE THERMOSTATS
• ZONE SUPPLY & RETURN HEADERS
• PIPE & FITTINGS TO ZONES
• EXPANSION TANK
ELECTRICAL
• HEAT PUMP SERVICE WIRE 6-3 OR 8-3
• BUFFER TANK ELEMENT SERVICE WIRE
• HEAT PUMP BREAKER
• BUFFER TANK ELEMENT BREAKER
• ELEMENT CONTACTOR & ELEC. BOX (IF NOT WITH TANK)
• THERMOSTAT WIRE 18-4
• THERMOSTAT WIRE 18-2
• FORK TERMINALS FOR TSTAT WIRE (6)
• 2” STYROFOAM INSUL. (IF PAD NOT PURCHASED)

ISSUE 04: 23-Sep-2022 Page 14 002500MAN-01
Wiring
Power Supply Connections
Power supply for the heat pump from the breaker panel is
supplied to the unit via concentric 1.093” / 0.875” knockouts.
There are also several 0.875” knockouts and a 3/8” plastic
grommet for electrical connections to the indoor circulator,
ground loop circulator pump, and controls.
A schematic diagram (SCH) and electrical box layout
diagram (ELB) can be found on the electrical box cover of the
unit as well as in the Model Specific Information section of this
manual. The Electrical Tables in the Model Specific Infor-
mation section contain information about the wire and breaker
per the voltage of the circulator pump module. Ground wire
should be connected to the ground lug in the electrical box.
Ensure that the total current draw does not exceed the value
indicated on the label in the heat pump electrical box.
For 460/575VAC models, 24VAC and ground are provid-
ed on the terminal strip for use with an external contactor to
control the circulator pump module.
NOTE: A properly qualified electrician
should be retained for all connections to the
heat pump and associated controls.
TABLE 4 - Power Supply Connections
Line Description Voltages
L1 Line 1 All
L2 Line 2 All
L3 Line 3 3-phase only
GND Ground All (connect to ground lug)
** For 208/230-1-60 and 208-3-60, N is required only if connect-
ing 115VAC circulators to the unit. The heat pump itself does
not require a neutral.
For 380-3-50, N is not required if not using desuperheater
and not connecting 220V circulators to the unit.
N** Neutral 208/230-1-60, 208-3-60, 380-3-50
Indoor Circulator Pump Wiring
The indoor loop circulator provides flow between the heat
pump and the buffer tank, and is powered from the heat pump.
The heat pump has provisions for connecting the indoor circula-
tor pump so that it will be turned on whenever the compressor
operates, and also when sampling water temperature during the
use of the Setpoint Control feature.
Connect the circulator pump to the appropriate two termi-
nals (115VAC or 230VAC) of the terminal strip marked INDOOR
CIRCULATORS in the heat pump, as per the voltage of the
circulator pump. Ground wire should be connected to the
ground lug in the electrical box. Ensure that the total current
draw does not exceed the value indicated on the label in the
heat pump electrical box.
For 460/575VAC models, 24VAC and ground are provid-
ed on the terminal strip for use with an external contactor to
control the circulator. Refer to the schematic and electrical box
drawings in the Model Specific Information section and on the
electrical box cover for more information.
Outdoor Loop Pump Module Wiring
(Ground Loop Only)
The heat pump has provisions for connecting the circulator
pump module so that the pumps will be turned on whenever the
compressor operates. Connect the circulator pump module to
the appropriate two terminals (115V or 230V) of the terminal
strip marked OUTDOOR CIRCULATORS in the heat pump, as
Control Transformer
The low voltage controls for 208/230-1-60 and 208-3-60
models are powered by a class II transformer with resettable
breaker on the secondary side for circuit protection. Should the
breaker trip, locate and correct the problem and then reset the
breaker by pressing in on it.
All other voltage models have a transformer with primary
and secondary fuses for circuit protection.
TABLE 5 - Indoor & Outdoor Circulator Connections
Terminal Description
115V Connection for 115V circulator
115V
230V
230V
Use a 2-conductor 14ga cable.
Connection for 230V circulator
IMPORTANT NOTE: For 208/230VAC-1-60
units, if connecting to 208VAC power supply
move the red wire connected to the 240 ter-
minal of the transformer to the 208 terminal
of the transformer.
Open/Closed Loop Wiring
The heat pump is provided configured for closed loop op-
eration. For open loop operation, the jumper plug must be re-
moved from the wiring harness found behind the pipe post and
the water valve harness plugged in. This will select the proper
temperature limit settings (although there may be no difference
between the open/closed loop settings for WH). See the “Water
Valve” section in the Open Loop Installations chapter for details.
A modulating water valve may be required; see Piping &
Open Loop Installation chapters, and wiring diagram in Model
Specific Information section.
Domestic Hot Water (Desuperheater)
The desuperheater function on HACW/HW models is pre-
wired and no field connections are necessary.
After the desuperheater is filled with water and purged of
air, activate the built-in DHW circulator by connecting the brown
wire with the blue insulated terminal to L1 of the compressor
contactor as shown on the wiring diagram in the Model Specific
Information section. Ensure the power is off when connect-
ing the wire. Also, turn on the DHW ON/OFF switch.
12VDC from
bottom of board
IMPORTANT NOTE FOR 3-PHASE UNITS: If
on startup compressor is noisy and not
pumping, reverse L1 and L2 supply wires.

ISSUE 04: 23-Sep-2022 Page 15 002500MAN-01
Both D1-D2 and D2-CD default to ON and so
must be used with an auxiliary heating device
that has a HIGH TEMPERATURE LIMITER to
avoid a serious safety hazard.
Aquastat Connections (Optional)
Most installations will use the internal Setpoint Control
routine to control buffer tank temperature. However, an aq-
uastat or external controller can be used if required, for example
if heating two loops with different setpoint temperatures, or us-
ing a time-of-day or lead/lag third-party programmable control-
ler. This is Signals or Hardwired Control.
The CA, RA, Y1A, & Y2A connections are located on the
right side towards the top of the control board, as shown on the
wiring diagram in the Model Specific Information section. The
external device needs to send the 24VAC signal from RA back
to the Y1A/Y2A terminals to call for compressor. CA is the com-
mon terminal for use in powering the external device.
TABLE 9 - Aquastat (Signals Control) Connections
Signal Description
CA 24VAC common (ground)
RA 24VAC hot
Y1A Compressor ON
Y2A Compressor stage 2 (not present for WH)
Use an 18ga cable.
Setpoint Control Connections
If using the on-board Setpoint Control routine with sam-
pling option (ICR) to control buffer tank temperature, no external
temperature probe or aquastat is required. For either Setpoint
Control option (ICR or HTS/CTS), only one control connection is
required, and only for reversing models: a dry contact from R
(24VAC) to O on the terminal strip to switch the heat pump into
cooling mode. C (ground) 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 8 - Setpoint Control: Aux. Connections
Signal Description
D1 Hydronic Auxiliary dry contacts
D2
R
D1
D2 24vac to actuate aux. heat contactor coil
CD Contactor coil ground
Use a 2-conductor 18ga cable.
Jumper R and D1
TABLE 7 - 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, 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 2 methods for acti-
vating hydronic auxiliary heat. See diagram on following page.
First, a dry contact on terminals D1 and D2 is available, to
actuate a heating device that has its own temperature controller
and transformer. 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 Ther-
mo2000 AltSource tank that is available from Maritime Geo-
thermal as an accessory; see the setup instruction sheet that
comes with tank and on a following page.
Second, a 24VAC signal can be used to power the coil of
an external contactor to operate auxiliary heat. Choose this
method if using a heating device that doesn’t have its own elec-
tronic controller or control transformer, e.g. a bare heating ele-
ment in the buffer tank. As per the diagram on the following
page, connect a jumper between R and D1 on the terminal strip,
and use D2 and CD to power the coil of the external contactor.
Under this method, the auxiliary heat also defaults to ON (as
long as the heat pump is powered ON to provide 24VAC), so the
tank’s temperature limiter must remain in operation.
Disable Switch (field installed)
A switch or dry contact to disable demand from the con-
trol system may be installed. On control board, jumper COM_IN
to GND, and toggle 12VDC to IN_SPARE to disable. See wiring
diagrams in the Model Specific Information section.
Summer Setback Switch (field installed)
A switch to enable summer setback mode may be in-
stalled. On control board, toggle R to PM2 to enable. See wir-
ing diagrams in the Model Specific Information section.
Summer setback disables stage 3 (AUX), drops setpoints
to 70°F (21°C), and decreases temperature sampling frequency
to 2 days. Can also be enabled through PC App or LCD.
Other Connections
Hot tank and/or cold tank temperature sensors can be
used in place of the ICR sampling routine with Setpoint Control.
This is the HTS/CTS option.
A 3-way valve can be controlled from the heat pump’s L3
output, for use with the HTS/CTS 2-tank auto-maintain feature.
An accessory current sensor can be installed, for com-
pressor status monitoring.
An accessory outdoor temperature sensor, to enable
Outdoor Reset functionality.
See the following chapters and the schematic (wiring)
diagram in the Model Specific Information section for details.
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 6 - BACnet Connections
Line Description
A Communication +
B Communication -
GND Ground
Use a shielded twisted pair cable.

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