Northern Heatpump RT-SE* Manual

09/29/2010 NI501
Two-Stage Split Geothermal Heat Pump
Installation & Operating Instructions
Model: (RT-SE*)
Application
Retrofit existing forced air installations.
Dual Heat – combine this geothermal unit and A-coil with stand-by gas or oil furnace.
LMC (Load management control) ready.
Information
The air coil furnished with this product has been tested and
certified with this unit. To maintain the specification
performance and product certification, the air coil shipped with
this unit must be used.
This unit is NOT tax credit eligible when a coil other than the
furnished coil is used.
For proper performance, the CFM airflow required in the
specification table must be provided by the installed furnace
blower/air handler.
Since this product requires line sets and air coil installation, an
experienced and licensed refrigeration technician is required.
Domestic Water Heater, Desuperheater
Energy Star promotes the desuperheater and it is standard with this series. However, it only efficiently
produces hot water if the tank temperature is less than 115° F (46° C). Thus, for proper and efficient
application a hot water buffer tank is suggested, see page 17.
Note
The EZGEO control board has a configuration mode dial switch. This must be correctly set during
installation, see EZGEO Controller (HC112) and Field Setup sections.
Drawings: EC001, HC112, NH501, NR501, NS501, XX029
DO NOT DESTROY THIS MANUAL. PLEASE READ CAREFULLY AND KEEP IN A SAFE
PLACE FOR FUTURE REFERENCE BY A SERVICE TECHNICIAN.

09/29/2010 NI501
Table of Contents
Introduction 1
Product Configurator (NC029) 2
Mechanical Specifications 3
Electrical Data 4
Product Dimensions 5
Installation Requirements 6
Mechanical Installation Overview 7
Mechanical Installation Source Water 9
Flushing and Filling Procedure 11
Desuperheater, Domestic Hot Water 16
Duct System/A-Coil 18
Mechanical Installation Refrigeration 19
Charging Procedure 21
Superheat and Subcooling 22
Electrical Hookup 25
EZGEO Controller 26
Temperature Sensors, Field Install 29
Gas Furnace Hookup – Mode D 30
Additional Hookup or Special Equipment Concerns 31
Field Setup or Programming 32
Operation Indicators 34
Power On, Start Up 35
Operational Tips 36
Troubleshooting 37
Accessories/Options 42
Drawings EC001
HC112
NH501
NR501
NS501
XX029

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Introduction
When used and controlled properly, geothermal heat pumps can save hundreds of dollars in heating and cooling
costs per year. Northern Heat Pump NorthStar Series geothermal heat pumps are designed to provide maximum
efficiency, comfort, and reliability. Solid and simple electric controls allow for low maintenance and built in
safety protection.
This is a pre-wired package for converting a new or existing oil or gas furnace into a dual heat system. This is a
complete package for both heating and air conditioning, utility load control, and compatible with DC drive
variable speed furnaces. There are no additional relays or option hardware needed for the outlined application.
The utility load control receiver properly switches the heating mode and properly controls the air conditioning
mode during summer load interrupt. The blower circuit and control is also designed for heating interrupt
(blower handled by gas furnace only) and continuous operating blower during cooling peak load interrupt.
Typically these controls and design features are only found in this product.
Moving and Storage
Units should be stored in original packaging in a clean dry area. Store and move units in normal upright
position. Do not stack units.
Initial Inspection
Be certain to inspect all cartons and crates as units are received before signing the freight bill. Verify that all
items received have no physical damage. Report any damages or shortages on the freight bill. The purchaser is
responsible for filing the necessary claims with the carrier. Concealed or hidden damages not discovered until
removing packaging must be reported to the carrier within 15 days of receipt.
Unit Location and Mounting
Locate the unit in an indoor area where the ambient temperature will remain above 45°F [8°C]. Northern Heat
Pump provides 4 removable panels for ease of servicing; front (2), right and left bottom. This unit is zero
clearance rated; however, allow enough room to remove panels for service and maintenance. Suggest setting
unit on a sound vibration pad, see accessories price sheet, R-PAD-2735-1-**. Water supply should not be hard
plumbed directly with copper pipe as this could transfer any vibration to living space.
Please read and understand conditions associated with proper installation, unauthorized changes, and POWER ON
procedures.
Warranty Statement
See the last page of this manual for detailed limited warranty coverage explanation.
Safety Considerations
WARNING
BEFORE PERFORMING SERVICE OR MAINTENANCE OPERATIONS ON A SYSTEM, TURN OFF
MAIN POWER SWITCHES TO THE INDOOR UNIT. IF APPLICABLE, TURN OFF THE ACCESSORY
HEATER POWER SWITCH. ELECTRICAL SHOCK COULD CAUSE PERSONAL INJURY.
Installing and servicing heating and air conditioning equipment can be hazardous due to system pressure and
electrical components. Only trained and qualified service personnel should install, repair or service heating and
air conditioning equipment. Untrained personnel can perform the basic maintenance functions of cleaning coils
and cleaning and replacing filters. All other operations should be performed by trained service personnel.
When working on heating and air conditioning equipment, observe precautions in the literature, tags and labels
attached to the unit and other safety precautions that may apply, such as the following safety measures:
Follow all safety codes.
Wear safety glasses and work gloves.
Use a quenching cloth for brazing operations.
Have a fire extinguisher available for all brazing operations.

09/17/2010 NC029
Northern Heat Pump Configurator
RT-SE-052-1-CXDX1-XX-US
Geo Source (1)
Unit Type (2)
T = Two Stage
Unit Style (3)
S = Split
Refrigerant (4)
E = R-410A
Nominal BTU (5, 6, 7)
020 = 1.5-ton
026 = 2.0-ton
033 = 2.5-ton
040 = 3.0-ton
045 = 3.5-ton
052 = 4.0-ton
062 = 5.0-ton
Country of Origin (16, 17)
US = United States
Auxiliary kW Option (14, 15)
XX = None
Vintage (13)
1
Miscellaneous Kits (12)
X = None
Desuperheater Option (11)
D = Desuperheater w/ Factory
Installed Pump
X = None
Configuration Option (10)
C = Split Air Coil
X = No Split Air Coil
Heat Exchanger Option (9)
C = Copper
Voltage Option (8)
1 = 208/230V, 1 Ph
2 = 208/230V, 3 Ph
Split System Coils
R-AE-030-21-US
R = Geo
Always A
Refrigerant
E = R-410A
Coil Size
21 = 21”
24 = 24”
Coil Capacity
024 = 24k BTU (2-ton)
036 = 36k BTU (3-ton)
048 = 48k BTU (4-ton)
060 = 60k BTU (5-ton)
R T - S E - 0 5 2 - 1 - C X D X 1 - X X - U S
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Model Number Digits

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Mechanical Specifications – R410A Two-Stage Compressor
MODEL RT-SE-020
(1.5 ton)
RT-SE-026
(2 ton)
RT-SE-033
(2.5 ton)
RT-SE-040
(3 ton)
RT-SE-052
(4 ton) RT-SE-062 (5 ton)
Coax & Piping Water Volume – gal .43 .43 .65 .65 1.1 1.1
Internal Pressure Drop (feet) 6.2 6.2 4.2 5.5 6.2 8.0
Internal Pressure Drop (psi) 2.7 2.7 1.8 2.4 2.7 3.5
Source Temperature °F (min/max) 20°/120° 20°/120° 20°/120° 20°/120° 20°/120° 20°/120°
Nominal source differential* ° F (H/C) 3/10° 3/12° 8/11° 9/11° 6/11° 6/10°
Factory Charge R410A -(oz) * 40 46 46 64 96 96
Static Pressure – Nominal 0.3 0.3 0.3 0.3 0.3 0.3
Static Pressure – Design 0.5 0.5 0.5 0.5 0.5 0.5
Air Filter 7/8 X 21 7/8
X 27 1/2
7/8 X 21 7/8
X 27 1/2 7/8 X 21 7/8
X 27 1/2 7/8 X 28 7/8 X 27 1/2 7/8 X 27 1/2 X 37 7/8 7/8 X 27 1/2 X 37 7/8
Weight– Packaged (lbs) 420 440 460 480 503 530
*Shown as reference information only, see unit nameplate for the supplied factory charge for each specific unit.
HEATING – ISO 13256-1 SPECIFICATION – ENERGY STAR
WLHP – Water Loop GWHP – Ground Water GLHP – Ground Loop
68° F 68° F 50° F 68° F 32° F/41° F 68° F
Model Stage
Source
GPM Capacity
Btu/h
Blower
CFM
Temp
Rise COP Capacity Btu/h
Blower
CFM
Temp
Rise COP Capacity Btu/h
Blower
CFM
Temp
Rise COP
RT-SE-026 FL 7 35.49 900 39 4.52 29.70 900 32 4.24 24.47 900 26 3.82
RT-SE-026 PL 7 24.39 700 33 4.60 21.68 700 29 4.30 18.74 700 26 3.84
RT-SE-033 FL 8 41.36 940 42 4.04 36.30 950 36 3.95 27.65 950 28 3.49
RT-SE-033 PL 8 28.45 720 38 4.66 23.40 700 32 4.02 20.80 714 28 3.73
RT-SE-040 FL 10 52.00 1210 41 4.51 42.72 1205 34 4.27 33.19 1200 27 3.72
RT-SE-040 PL 10 37.47 1020 35 5.47 30.80 1000 30 4.72 27.28 1000 26 4.26
RT-SE-052 FL 13 68.18 1500 43 4.00 53.31 1500 36 3.72 44.93 1500 29 3.31
RT-SE-052 PL 13 47.09 1200 37 4.40 37.75 1200 30 3.72 33.75 1180 27 3.43
RT-SE-062 FL 15 81.87 1840 35 4.02 66.71 1840 35 4.02 53.35 1820 28 3.57
RT-SE-062 PL 15 63.45 1520 40 4.88 50.00 1470 32 4.11 45.40 1475 29 3.82
COOLING – ISO 13256-1 SPECIFICATION – ENERGY STAR
WLHP – Water Loop GWHP – Ground Water GLHP – Ground Loop
86° F 80.6° F 59° F 80.6° F 77° F/68° F 80.6° F
Model Stage
Source
GPM Capacity
Btu/h
Blower
CFM
Temp
Drop EER Capacity Btu/h
Blower
CFM
Temp
Drop EER Capacity Btu/h
Blower
CFM
Temp
Drop EER
RT-SE-026 FL 7 32.46 950 20 13.4 36.87 950 22 20.3 30.17 950 20 16.06
RT-SE-026 PL 7 24.35 750 20 14.5 28.00 750 21 22.0 22.66 750 22 19.2
RT-SE-033 FL 8 33.71 1000 20 14.2 38.87 1000 22 20.5 36.06 1000 21 15.9
RT-SE-033 PL 8 25.28 730 22 13.3 29.16 740 25 21.3 27.05 750 24 18.0
RT-SE-040 FL 10 42.28 1260 22 13.9 47.48 1260 23 20.0 44.68 1260 22 16.1
RT-SE-040 PL 10 31.69 1055 21 17.0 35.55 1055 22 27.1 34.92 1060 21 23.1
RT-SE-052 FL 13 55.75 1600 22 12.9 64.95 1600 23 19.1 58.00 1600 22 15.1
RT-SE-052 PL 13 41.70 1300 20 14.8 48.28 1275 22 24.4 46.63 1275 22 21.4
RT-SE-062 FL 15 71.21 1970 21 14.2 76.65 1970 23 18.7 72.60 1970 23 15.6
RT-SE-062 PL 15 54.06 1600 22 16.2 57.50 1630 21 23.1 60.34 1670 22 22.1
1. Capacities are based on temperatures shown in heading, source is left group, return air is right group.
2. Stated Btu/h are the ISO 13256-1 formula adjusted, actual HP supply energy delivered is 2% greater.
3. Temp rise is based on sensible only.
4. All ratings based upon operation at lower voltage of dual voltage rated models.
5. Ground Loop Heat Pump ratings based on 15% antifreeze solution.

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Electrical Data – Single Phase
Voltage Compressor Desup.
Pump
Loop
Pump
(Ext) Total Min.
Model
(60 Hz) RLA LRA FLA FLA FLA Ampac.
Max.
Fuse/
HACR
020 208/230-1 10.3 52 .15 4.4 14.9 17.4 30
026 208/230-1 14.1 70 .15 4.4 18.7 22.2 40
033 208/230-1 16.7 82 .15 4.4 21.3 25.4 50
040 208/230-1 16.7 96 .15 4.4 21.3 25.4 50
052 208/230-1 25.6 118 .15 4.4 30.2 36.6 60
062 208/230-1 27.2 150 .15 4.4 31.8 38.6 60
Electrical Data – Three-Phase
Voltage Compressor Desup.
Pump
Loop
Pump
(Ext) Total Min.
Model
(60 Hz) RLA LRA FLA FLA FLA Ampac.
Max.
Fuse/
HACR
020 200/230-3 7.1 59 .15 4.4 11.7 13.4 30
033 200/230-3 11.2 58 .15 4.4 15.8 18.6 40
040 200/230-3 13.5 88 .15 4.4 18.1 21.4 40
052 200/230-3 17.6 123 .15 4.4 22.2 26.6 50

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Product Dimensions

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Installation Requirements
1. All installation work must be performed by trained, qualified contractors or technicians. Northern Heat
Pump, sponsors installation and service schools to assist the installer. Visit our Website at
www.electromn.com for upcoming service schools.
WARNING
ALL ELECTRICAL WIRING MUST BE IN ACCORDANCE WITH NATIONAL ELECTRIC CODE
AND LOCAL ELECTRIC CODES, ORDINANCES, AND REGULATIONS.
WARNING
OBSERVE ELECTRIC POLARITY AND WIRING COLORS. FAILURE TO OBSERVE COULD
CAUSE ELECTRIC SHOCK AND/OR DAMAGE TO THE EQUIPMENT.
CAUTION
This unit can only be used for its intended design as described in this manual. Any internal
wiring changes, modifications to the circuit board, modifications or bypass of any controls, or
installation practices not according to the details of this manual will void the product warranty,
the safety certification label, and manufacturer product liability. Northern Heat Pump, cannot
be held responsible for field modifications, incorrect installations, and conditions which may
bypass or compromise the built-in safety features and controls.
2. If this is a Dual Heat system, this product relates only to the addition to the furnace ducting system external
to the gas or oil force air furnace. The owner/ installer assumes all responsibility and/or liability associated
with any needed installation of the gas/oil furnace, fuel system, flue, chimney, etc. Any instructions or
comments made within this manual (or factory phone assistance) relating to the gas/oil furnace are provided
as comments of assistance and “helps” only.
CAUTION
This unit shall not be operated (either heating section or blower) until the interior of the
structure is completed and cleaned. This also means all duct work must be complete with filter,
etc. Manufacturer’s warranty is void if this unit is operated during structure construction.
CAUTION
Hazards or unsafe practices could result in property damage, product damage, severe personal
injury and/or death.
3. All removed or discharged refrigerant must be recovered. Local and federal statutes are to be observed.
Should a compressor need replacing, the compressor oil is to remain with the compressor. Refrigerant lines
on the compressor must be sealed.
4. Remember, safety is the installer’s responsibility and the installer must know this product well enough to
instruct the end user on its safe use.
At Northern Heat Pump, the safety of the installer and the end user is of highest priority. Remember, safety
is the installer’s responsibility and the installer must know this product well enough to instruct the end user
on its safe use. Professional installers should be trained and experienced in the areas of handling electrical
components, sheet metal products, and material handling processes.

09/29/2010 7 NI501
Mechanical Installation Overview
This NHP Series unit cannot produce airflow and cannot correct airflow problems inherent within the existing
furnace system. The following items should be carefully considered and properly followed for all installations:
Examination of the existing forced air furnace – Prior to starting this installation or furnace modification,
examine the total furnace system and make necessary comments or recommendations to the homeowner.
Remember, if a marginal condition exists within the existing forced air system, the installation of a geothermal
heat pump will not cure PRE-EXISTING conditions. Consider such items as proper fossil fuel ignition, is the
furnace cycling on hi-limit, filter, adequate cold air return, adequate supply duct and room register (1 register
per 100 CFM) etc.
Heating capacity – Size the geothermal heat pump according to the normal heating requirements as the building
exists today. Do not necessarily match to the existing furnace nameplate because it may be oversized. Do not
oversize the geothermal heat pump.
Supply plenum – Carefully examine all sides of the plenum. The coil must be installed on the supply side of
the fossil fuel furnace. Verify all transitions have angles less than 30, the coil is centered within the plenum,
and there are no odd shaped angles or odd shaped transitions within the plenum.
Other plenum equipment – Auxiliary equipment such as humidifiers, zone plenum dampers, etc., located
within the plenum which may cause a non-uniform airflow issues may have to be removed if they cause to great
reduction to system airflow. Zone dampers within the trunk line at least 12" (30cm) from the coil typically are
no problem. When horizontal zone dampers are involved, perform all check-out functions with smallest zone
open first.
Comment – zone dampers cause back pressure on the blower and overall reduced airflow. Reduced
airflow can cause the geothermal unit to perform poorly or in some cases cause icing or freeze ups in the
geo loop or air coil.
Insufficient cold air return capacity – Installation experience indicates this is a major concern. In fact, it
could represent a problem in as many as 60% of the installations, especially if there is a requirement to increase
airflow with the existing blower and the existing cold air return capacity is already undersized or restricted.
Check the static pressure within the return cabinet or the suction at the filter cabinet door. Do not assume
because there is a register on the wall, the hole behind the register or the passageways are equal to this register.
Sharp offsets and transitions in the cold air return system often cause severe restrictions. Expect to add
additional registers or a relief register in the main cold air return duct.
Blower CFM capacity – The furnace forced air system must have an airflow capacity larger than the minimum
requirement on the NHP Series specification sheet (see unit nameplate and/or Mechanical Specifications on
page 3). It is near impossible to correctly measure CFM airflow in an existing residential installation.
Experience and rule of thumb indicators will have to be followed to determine the existing furnace CFM
capacity. The following may be helpful:
a. Existing furnace nameplate - Typically represents a high or optimistic rating and is a function of
the systems static pressure. What changes have been made to the heating system since
installation?
b. Blower motor size - Used only as a minimal guide.
2 ton unit - 1/3 HP or larger
3 ton unit - 1/2 HP or larger
4 ton unit - 3/4 HP or larger
5 ton unit - 1 HP or larger
c. Observe/examine airflow ducting system and design - Use duct sizing table (ECØØ1), or
industry equivalent duct capacity airflow charts and determine if the system is capable of
delivering the CFM required on the nameplate. Especially check the number of registers and

09/29/2010 8 NI501
Figure 1
Horizontal Closed Loop
the number of “6 inch rounds”. The same would apply to cold air return duct capacity.
d. Calculated CFM - By measuring the temperature rise across the existing furnace, the CFM can
be approximated. The accuracy of this formula will depend upon the estimated or determined
Btu output (actual heat energy across the furnace, not nameplate input).
Btuh (output)
CFM = Temperature Rise x 1.08
Closed Loop Applications – Closed loop system re-circulates the same water/antifreeze solution through a
closed system of underground high-density polyethylene pipe. As the solution passes
through the pipe it collects heat (in the heating mode) that is being
transferred from the relatively warm surrounding soil through the pipe
and into the relatively cold solution. The solution is circulated back to
the heat pump that extracts its heat and then returns to the ground to
absorb more heat from the earth. Earth loops must be sized properly for
each particular geographic area and individual capacity requirements.
The NHP Series heat pumps are designed to
operate on either vertical or horizontal closed loop applications. (Figures 1 & 2)
Vertical loops are typically installed with a well drilling rig up to 200 feet (61
meters) deep or more. Horizontal systems are typically installed with excavating
or trenching equipment approximately six to
eight feet deep, depending on geographic
location and length of pipe used.
Lake or Pond Loops – Closed loop systems may also be used in lakes or
rivers to supply a heat source to the heat pump. Typically a loop consisting
of geothermal pipe can be designed and placed in an area not much deeper
than 15ft (4.5 meters) with some water currents present. In any lake or
pond, municipal and area codes must be observed in regards to a lake or
pond loop. The use of an environmentally friendly loop fluid like ethanol
should be considered should damage ever occur to the loop. Consult an IGSHPA
or CGC certified installer for proper lake or pond loop design.
Figure 2
Vertical Closed Loo
p

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Figure 3
P/T Adapter
Mechanical Installation Source Water
WARNING
LOOP DESIGN IS EXTREMELY IMPORTANT FOR PROPER HEAT PUMP OPERATION.
INCORRECT LOOP DESIGN WILL REDUCE HEAT PUMP EFFICIENCY, CAUSE POOR
PERFORMANCE OR MAY RENDER THE SYSTEM UNUSABLE. CONTACT AN IGSHPA OR
CGC CERTIFIED GEOTHERMAL LOOP CONTRACTOR FOR PROPER INSTALLATIONS.
Water Connections General
The following pages outline typical piping arrangements for the most common source water connection options,
as well as flushing and filling procedures and antifreeze requirements for closed loop systems. Do not connect
copper piping directly to the source water connection points on this unit. A section of flexible piping is
recommended to reduce and isolate vibrations transmitting from the compressor into other parts of the system.
Once closed loops are completed, they must be pressure tested to at least 60 PSI to insure integrity. Once
pressure is tested, loop must be purged of all foreign debris and filled with fluid. All air must be removed at this
time by flushing the system. (Table 2) shows approximate fluid volumes.
Pressure/Temperature (P/T) plugs – Should be installed in the adaptor elbow on the entering
and leaving water line of the heat pump on a closed system. (Figure 3) A thermometer can be
inserted into the P/T ports to check entering and leaving water temperatures. A pressure gauge
can also be inserted into these P/T ports to determine the pressure differential between the
entering and leaving water. This pressure differential can then be compared to the engineering
specifications data to determine the flow rate of the system.
Loop Pump Selection – Select a loop circulation pump based upon the GPM required and total system pressure
drop. See specification, page 3. Geo heat pump Btu/h capacity and efficiency are directly related to the GPM
flow though the unit.
Vibration pad – suggest setting the unit on a sound vibration pad, available from most distributors or
accessories price sheet – R-PAD-2735-1-**.
Water quality – models with standard copper heat exchanger coils require the installer to evaluate water quality
and meet minimum water properties.
pH/calcium hardness pH < 7.5 and Ca harness < 100 PPM
Iron fouling < 0.2 PPM (Ferrous)
< 0.5 PPM of oxygen
Hydrogen sulfide (H2S) < 0.5 PPM
Chloride levels < 20 PPM
Erosion/clogging < 10 PPM, particles
Filter, if required < 800 micron size

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Figure 4 – Pressurized Closed Loop with Flow Center – Typical piping arrangement.
Figure 5 – Non-Pressurized Closed Loop with Flow Center – Typical piping diagram.

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To Earth Loop
From Earth Loop
From
Flush
Cart
To
Flush
Cart
Step 3
From Heat Pum
p
To Heat Pum
p
Ste
p
5
To
Flush
Cart
From
Flush
Cart
From Heat Pump
T
o
H
eat
P
u
m
p
To Earth Loop
From Earth Loop
Step 6B
From Heat Pum
p
To Heat Pum
p
Ste
p
6A
From
Flush
Cart
Pressurize Loo
p
Flushing and Filling the System Using 3-Way Valves
Step 1
Use water and a high volume head circulator pump to flush air and debris and to fill the loop system.
Refer to recommendations provided by IGSHPA or CGC when choosing a pump for the flushing
process.
It is recommended that pump suction be from the bottom of a large volume container. Use a suction
line strainer to prevent debris discharged into the container from being recycled to the system.
Step 2
Pump water into the system by connecting the pump discharge hose to one (not both) of the 1.00” NPT water
connections located on the sides of the module.
Connect a return hose to the opposite side of the module to discharge debris and air as water is added to the
loop.
Step 3
Rotate the module valves as shown in step 3 diagram:
Step 4
Start the pump. Add anti-freeze and water to the container as needed so that no air enters the system. This will
push any air out of the loop. If flushing assembly is equipped with valves to reverse flow direction, do so
occasionally to help remove trapped air. When bubbles cease in the return hose container, the earth loop has
been completely flushed.
Step 5
Flush the heat pump. To do so, simply rotate the valves as
shown in step 5 diagram while the pump is running. Flush
the heat pump using the same procedure as used to flush the
earth loop.
Pressurizing the System (does not apply to Figure 5)
Step 6
After flushing and filling the system, rotate the module valve
discharging into the flush container as shown in step 6A
diagram to pressurize the loop. Then turn the valves as in
step 6B.
Step 7
Turn off the flush cart pump. The system should remain
pressurized. Release excess pressure by rotating either
module valve to allow a small amount of water to pass
through and out of the system and into the container. Some
initial loss of pressure can be expected and is due to the
expansion of the earth loop pipe under pressure. The pressure
will stabilize if the system has no leaks.
Step 8
Flushing, filling and pressurization should be complete. Start
the loop pump module circulators.
Step 9
Troubleshoot. If for some reason the circulators are not
operating, power off and diagnose the problem.
Step 10

09/29/2010 12 NI501
Using a single water pressure gauge, measure the pressure drop at the pressure/temperature plugs across the heat
pump heat exchanger. Compare the measurement with the flow versus the pressure drop table (Table#3) and
determine the actual flow rate. If the flow rate is low, recheck the selection of the loop pump module model for
sufficient capacity. If the model is correct, there is likely trapped air or a restriction in the flow circuit.
System pressure should increase rapidly as the flush pump works to force more water into the system.
Additional flushing of the loop is needed if the water level in the loop falls. This shows that there is air in the
system. System operating pressures should be between 10 to 40 PSI.
Antifreeze
DO NOT mix more than 25% propylene glycol with water to achieve a lower than 15°F [-9°C] freeze
protection. (See Table 3) A more concentrated mixture cannot be pumped through the earth loop at low
temperatures. Lack of antifreeze will cause unit shutdown problems during cold weather operation (longest unit
run time) when the loop temperatures fall below the freeze protection of the antifreeze. Flow rate requirements
for closed loop solutions are higher than open loop systems because water temperatures supplied to the heat
pump are generally lower. Typically 2.0 to 3.0 gallons per minute (GPM) per ton are required for proper
operation of the heat pump and the earth coupled heat exchanger.
Table 3 – Antifreeze Percentages by Volume*
Minimum Temperature for Freeze Protection
10°F 16°F 17°F 21°F 25°F
Type -12°C -9°C -8°C -6°C -4°C
Methanol 25% 21% 18% 16% 10%
Propylene
Glycol
38% 30% 25% 22% 15%
Ethanol 22% 20% 18% 14% 10%
*Reference information only, see product manufacturer
specification for percentage.
WARNING
DO NOT USE CALCIUM AS ANTI-FREEZE. FOLLOW CGC/IGSHPA RECOMMENDATIONS
FOR THE APPROPRIATE TYPE AND AMOUNT OF ANTI-FREEZE.
WARNING
PREVENTING FREEZE-UP IS INSTALLER/USER RESPONSIBILITY. LEAKING HEAT
EXCHANGER OR PIPING (EXTERNAL OR INTERNAL WITHIN THE REFRIGERANT/
COMPRESSOR) ARE NOT COVERED BY WARRANTY.
Table 2 – Approximate Fluid Volume (gal)
per 100ft
Pipe Size Volume
¾” IPS SDR 11 2.8
1” IPS SDR 11 4.5
1-1/4” IPS SDR 11 8.0
1-1/2” IPS SDR 11 10.9
Polyethylene
2” IPS SDR 11 18.0
Rubber Hose 1” 3.9
1” 4.1
1.25” 6.4
Copper
1.5” 9.2

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Open Loop Well to Well – An open system gets its name from the open discharge of water after it has been
used by the heat pump. A well must be available that can supply all of the water requirements of the heat pump
along with any other water requirements drawing off that same well. The well must be capable of supplying the
heat pumps required flow rated for up to 24 hours per day for the coldest winter day.
Figure 6 shows the necessary components for water piping of an open system. First a bladder type pressure tank
with a “draw down” of at least 1-1/2 to 2 times the well pump capacity must be installed on the supply side of
the heat pump to prevent short cycling the well pump. Shut off valves and boiler drains on the entering and
leaving water lines are necessary for future maintenance. A screen strainer is placed on the supply line with a
mesh size of 40 to 60 and enough surface area to allow for particle buildup between cleanings. Pressure
temperature (P/T) plugs are placed in the supply and discharge lines so that thermometers or pressure gauges can
be inserted into the water stream. On the well water discharge side of the heat pump a flow control/shut off
valve must be mounted to regulate the maximum water flow through the unit. Remove handle to prevent
accidental change of flow.
A solenoid valve is then installed and wired to TB C & Y terminal on the heat pump. (Refer to NS501) This
valve will open when the unit is running and close when the unit stops. A visual flow meter is then installed to
allow visual inspection of the flow requirements. The flow meter can also be useful in determining when
maintenance is required. Schedule 40 PVC piping, copper tubing, polyethylene or rubber hose can be used for
supply and discharge water lines. Limit rubber hose to 10 ft. (3 meters) to prevent excessive pressure drop.
Make sure line sizes are large enough to supply the required flow with a reasonable pressure drop (generally
1.00” diameter). Water discharge is generally made to a drain field, stream, pond, surface discharge, tile line, or
storm sewer.
CAUTION
Using a drain field requires soil conditions and adequate sizing to assure rapid percolation or
the required flow rates will not be achieved. Consult local codes and ordinances to assure
compliance. Do not discharge water to a septic system. The heat pump should never be
operated with flow rates (GPM) less than specified. Operation of the unit with less than
required flow rate or no flow may result in freezing water in the water to refrigerant heat
exchanger. This will cause the unit to shut down on low-pressure lockout. If the unit locks
out, verify that the unit has the required flow and reset the unit by shutting off power to the unit
for one minute. Do not continually reset the unit; if the unit locks out more than once call your
service professional. Continued reset of the unit can freeze water inside the water coil to the
point of rupturing the water coil (no warranty for frozen coils).

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Figure 6: Open Loop Well to Well – Typical piping diagram.
Open Loop Freeze Protection Switch – Heat pump installations on open loop systems, using a non-antifreeze
protected water source during the heating mode require the use of a water coil freeze protection switch. If the
water supply to the heat pump is interrupted for any reason, continued operation of the compressor will cause
the water remaining in the water-to-refrigerant heat exchanger to freeze and rupture. The freeze protection
switch will shut the unit down before freezing can occur and protect the heat pump against flow loss and
damage.
Option – 39° F (4° C) pipe clamp-on, part number 6047. Connect in series with low limit.
Water Coil Maintenance – Water quality is a major concern for open systems. Problems can occur from
scaling, particle buildup, suspended solids, corrosion, pH levels outside the 7-9 ranges, or biological growth. If
poor water quality is known to exist in your area a cupronickel water coil may be required when ordering the
system, or installing a closed loop system may be the best alternative. Water coil cleaning on an open loop
system may be necessary on a regular basis.

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Depending on the specific water quality issue, the water coil can be cleaned by the following methods:
Chlorine Cleaning (Bacterial Growth)
1. Turn thermostat to “Off” position.
2. Connect a circulating pump to hose bibs on entering water and leaving waterside of heat exchanger.
3. Using a five-gallon pail of water add chlorine bleach mixture. The chlorine should be strong enough to
kill the bacteria. Suggested initial mixture is 1 part chlorine bleach to 4 parts water.
4. Close shut off valves upstream and downstream of heat exchanger.
5. Open hose bibs to allow circulation of bleach solution.
6. Start pump and circulate solution through heat exchanger for 15 minutes to one hour. Solution should
change color to indicate the chlorine is killing the bacteria and removing it from the heat exchanger.
7. Flush used solution down the drain by adding fresh water supply. Flush until leaving water is clear.
8. Repeat procedure until solution runs clear through the chlorine circulation process.
9. Flush entire heat pump system with water. This procedure can be repeated annually, semiannually, or
as often as it takes to keep bacteria out of the heat exchanger, or when bacteria appears in a visual flow
meter to the point the flow cannot be read.
Muriatic Acid Cleaning
Difficult Scaling and Particle Buildup Problems
Consult installer due to dangerous nature of acids.
Iron out solutions and de-scaling products are also useful.

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Desuperheater, Domestic Hot Water
General
All NHP Series units are equipped with a desuperheater and an integrated circulating pump (can be a price
deduct) that can provide Supplemental Domestic hot Water (SDW). This is done by stripping heat from the
superheated gas leaving the compressor.
Fuses – 3-amp fuses are installed in series with the desuperheater pump. The fuses are located in the line
voltage control box, upper right. Remove the fuses (turn 230 power source off) to disable the pump whenever
the system is not in operation.
General Plumbing and Installation Suggestions
1. Insulated ½” copper piping should be used from the hot water tank to the desuperheater connections on
the left side of the unit. The copper tubing should be straight to maintain good water velocity and
prevent pockets from forming at the pump inlet.
CAUTION
Due to high water temperatures generated by the desuperheater, pex or poly pipe may rupture if
coupled directly to heat pump outlet.
2. Shut off valves should also be used to service the desuperheater pump without draining the entire hot
water tank. Note: Always be sure these valves are open when pump is running.
3. Pump problems develop by running the pump dry or with air in the system. All air must be purged from
the desuperheater plumbing before the pump is engaged.
4. To purge air from the lines, loosen the desuperheater pump from its housing by turning the brass collar.
Let water drip out of the housing until flow is established and re-tighten the brass collar.
5. Never operate the system without the high temperature switch (normally factory installed) otherwise
tank temperatures could become dangerously high.
6. Poor water quality may restrict the effectiveness of using the desuperheater pump and will not allow the
pump to circulate.
7. Desuperheater maintenance includes periodically opening the drain on the hot water tank to remove any
deposits. Hard water may cause scale buildup in the desuperheater coil reducing its effectiveness.
8. The temperature difference between the water entering and leaving the desuperheater should be 5°F to
15°F. The water flow should be approximately 0.4 GPM per ton of nominal cooling.
9. Northern Heat Pump strongly suggests a water heater buffer tank, Figure 7, for the maximum efficiency
from the provided desuperheater module. The Figure 7A single tank plumbing and application is shown
for information only.
There are a number of ways the desuperheater/pump can be plumbed with and into the building/household water
heater tank. However, many common methods used are not very effective because they simply circulate
already heated water from the water heater tank through the desuperheater. The heat pump desuperheater cannot
effectively produce hot water energy if the temperature of the water entering the desuperheater is close to or
beyond the compressor gas capability to transfer energy into this circulated water – typically 110° F (46° C) to
130° F (54° C).
Example – if the water heater electric element thermostat is set at 140° F (60° C), it will maintain
the tank at 140° F (60° C). There is no point in circulating 140° F (60° C) water through the
desuperheater because it is picking up very little or no energy from the compressor hot gas.
In fact, the energy flow may even be negative if the Geo HP loop temperature is too low, it is
possible for a single tank hot water heater to actually flow energy into the Geo HP system with a
negative effect of energy efficiency.

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Figure 7 – Desuperheater Piping, Buffer Tank
This is the most effective and efficient arrangement
and the recommended installation. The buffer tank
need not be as big as the standard water heater; 40-
gallon size can be very effective. With this two
tank system the desuperheater will always act as a
city/well water pre-heater and the standard water
heater (electric elements or gas) only requires
tempering energy which is a very small percentage
of domestic water heater energy required.
Figure 7A – Desuperheater, Single Tank Concept
Draw water from the bottom drain and returning it to the cold
water supply line. This method requires a check valve in the
cold water supply to prevent water from flowing into the
building or household cold water supply. A spring-type check
valve with a pressure rating of 1/2 PSI or less is recommended.
Inspect the dip tube in the water heater cold inlet for a check
valve. If a check valve is present it must be removed or damage
to the desuperheater circulator will occur.
Before restoring electrical supply to the water heater, adjust the
temperature setting on the tank.
On tanks with both upper and lower elements, the
lower element should be turned down to the lowest
setting, approximately 100° F (38° C). The upper
element should be adjusted to 120° F (49° C) to
130° F (54° C). Depending upon the specific needs
of the customer, you may want to adjust the upper
element differently.
On tanks with a single element, lower the
thermostat setting to 120° F (49° C).
CAUTION
Do not run desuperheater pump without supply from water heater. This will damage the pump.

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Duct System
An air filter must always be installed upstream of the air coil on the return air side of the air handler or furnace.
If there is limited access to the filter rack for normal maintenance, it is suggested that a return air filter grill be
installed. Be sure that the return duct is properly installed and free of leaks to prevent dirt and debris from
bypassing the filter and plugging the air coil.
In applications using galvanized metal ductwork, a flexible duct connector is recommended on both the supply
and return air plenums to minimize vibration from the blower. To maximize sound attenuation of the unit
blower, the supply and return plenums should include an internal duct liner of 1-inch thick glass fiber or be
constructed of ductboard. Insulation is usually not installed in the supply branch ducts. Ducts in unconditioned
areas should be wrapped with a minimum of 1-inch (25mm) duct insulation. Application of the unit to
uninsulated ductwork in an unconditioned space is not recommended as the unit’s performance will be adversely
affected. If the air handler is connected to existing ductwork, a previous check should have been made to assure
that the duct system has the capacity to handle the air required for the unit application. If ducting is too small,
as in replacement of heating only systems, larger ductwork should be installed. All existing ductwork should be
checked for leaks and repairs made accordingly. The duct system and diffusers should be sized to handle the
design airflow quietly. If air noise or excessive airflow is a problem, the blower speed can be changed to a
lower speed to reduce airflow. This will reduce the performance of the unit slightly in heating; however, it will
increase the temperature rise across the air coil. Airflow must still meet minimum requirements.
Air Coil Installation
This unit is furnished with the air coil matched to the heat pump system and compressor. To maintain the
product ratings, certification, etc. the furnished coil must be used.
Gas or Oil Furnace – Normally as required by the furnace manufacturer’s warranty, the refrigerant coil must be
in the supply or discharge plenum. It is recognized the furnished coil may be large and may present some
physical plenum issues, but it is matched to the size of the heat pump and thus this coil must be accommodated
within the forced air ducting system.
ST Duct Sensor – See page 29 for details relating to installing ST sensor above coil.
Airflow (CFM) – As listed on the unit nameplate and the page 3 specification table the minimum CFM must
flow through this coil. This is a function of the installer discerning the overall ducting system sizing/quality, the
furnace blower size/motor, furnace restrictions, return air restrictions, air filter, etc. This is not simply a
function of looking at the furnace nameplate. Proper CFM must be assured and guaranteed by the installer.
As the plenum is fabricated or rebuilt, all transitions must have angles of less than 30°, the coil must be centered
within the plenum, and there should not be any odd shaped angles or odd shaped transitions within the plenum.