Rheem 310 Series Operating instructions

First Issued March 2007
This document is stored and maintained electronically by Technical Support. All printed copies are deemed uncontrolled.
Rheem Australia Pty Ltd ABN 21 098 823 511
SERVICE INSTRUCTIONS
310 Series Heat Pump
TM025
Revision: AF
Issued: March 2016
Rheem
551310
Everhot
251310
Solahart
310HAV
Edwards
40467791

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
CONTENTS
INTRODUCTION .................................................................................................................3
SAFETY WARNING.............................................................................................................3
POWER SUPPLY................................................................................................................3
ENVIRONMENTAL..............................................................................................................3
HEATER MODEL IDENTIFICATION...................................................................................4
HEAT PUMP WATER HEATER MODELS ..........................................................................5
SPECIFICATIONS...............................................................................................................6
PREVENTATIVE MAINTENANCE ......................................................................................7
PRODUCT CHANGES ........................................................................................................8
REFRIGERATION TERMS AND THEIR MEANING..........................................................10
COMPONENTS AND THEIR FUNCTION .........................................................................11
CONTROLLER..................................................................................................................13
Power and Sensor Strip Connections.............................................................................13
Printed Circuit Board (PCB) ...........................................................................................14
Sensor Strip ...................................................................................................................14
Sensors..........................................................................................................................15
AUTOMATIC AIR ELIMINATOR........................................................................................15
OPERATION......................................................................................................................16
LED STATUS CODES.......................................................................................................24
OPERATIONAL SEQUENCES..........................................................................................25
Standby Mode and Heat Pump Mode ............................................................................25
Faults .............................................................................................................................28
Element Mode................................................................................................................30
WIRING DIAGRAMS .........................................................................................................32
Models manufactured from 31/03/16 (or fitted with a Grundfos Circ Kit from 04/16)......32
Models manufactured from 8/08/13 - 03/16 (or Grundfos Kit fitted during same range).33
Models manufactured from 14/08/2007 –7/08/2013 (Salmson Circulator) ....................34
Models manufactured prior to 14/08/2007 (Salmson Circulator) ....................................35
REFRIGERATION SYSTEM DIAGRAM............................................................................36
COMMON COMPLAINTS..................................................................................................36
SERVICE TECHNICIAN’S HEAT PUMP KIT.....................................................................38
SENSOR STRIP TESTER.................................................................................................39
FAULT FINDING................................................................................................................40
Sensor Strip and Sensor Strip Replacement Kit.............................................................70
Sensors..........................................................................................................................71
Refrigerant Charge.........................................................................................................81
Electrical Insulation Testing............................................................................................81
COMPONENT REPLACEMENT PROCEDURES .............................................................82
Storage Tank..................................................................................................................82
Heat Pump Module.........................................................................................................85
Refrigeration System......................................................................................................90
DOCUMENT REVISION HISTORY...................................................................................98

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
INTRODUCTION
The information provided in these instructions is based on the water heater being installed
in accordance with AS/NZS 3500.4, AS/NZS 3000 and the Owner’s Guide and Installation
Instructions booklet provided with each water heater.
Should you require further technical advice on a 310 Series Heat Pump Water Heater
contact Rheem Technical Support.
SAFETY WARNING
The purpose of this Service Manual is to provide sufficient information to allow a person
with the skills as required by the controlling Regulatory Authorities to carry out effective
repairs to a 310 Series Heat Pump Water Heater in the minimum amount of time.
Safety precautions or areas where extra care should be observed when conducting tests
outlined in this manual are indicated by print in bold italics and / or a warning symbol.
Take care to observe the recommended procedure.
General warning symbol. Observe the instructions accompanying the
symbol.
“Live” testing to be conducted. Personal Protective Clothing (PPE) shall
be worn to reduce the risk of electric shock. Refer to Rheem Safety
Procedure on electrical testing.
Isolate power before conducting the indicated test
Hot surface or liquid. Personal Protective Clothing (PPE) shall be worn to
reduce the risk of scalding.
WARNING: The heat pump must NEVER be operated with the refrigeration
system open to atmosphere.
POWER SUPPLY
310 Series Heat Pumps will only operate on a sine wave at a frequency of
50 Hz. Devices generating a square or saw tooth wave cannot be used to
supply power to the water heater.
ENVIRONMENTAL
R134a refrigerant is a controlled substance under the Ozone Protection
and Synthetic Greenhouse Gas Management Act. Only personnel qualified
and licensed to work with refrigerants may carry out service and repair
work on the sealed refrigeration system. During repair the refrigerant must
always be recovered, never vented to the atmosphere.
At the end of the service life of a Rheem heat pump, the refrigerant must
be recovered by personnel qualified and licensed to work with refrigerants
prior to the unit being disposed of. Refrigerants must not be vented to
atmosphere.

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
HEATER MODEL IDENTIFICATION
All identification numbers are designed to convey detailed information about the water
heater to which it is attached. Model number, serial number and date of manufacture
should be quoted in all correspondence.
Rheem / Everhot Model Identification
5
5
1
310
07
2 –Everhot
5 –Rheem
5 –Integrated
1 –Booster Element
310 - Storage Capacity in Litres
04 –1800 watt element
05 –2400 watt element
07 –3600 watt element
Solahart Model Identification
310
H
A
V
36
Storage Capacity in Litres
H –Heat Pump
A –Air Sourced
V –Warranty Code *
24 –2400 watt element
36 –3600 watt element
* For details refer to the product’s Owner’s Guide.
Edwards Model Identification
40
46
77
91
29
40 –Heat Pump
46 –310L Storage Capacity
77 –Joey Grey Colour
91 –With Heat Pump Module
28 –2400 watt element
29 –3600 watt element

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
HEAT PUMP WATER HEATER MODELS
The 310 Series Heat Pump consists of a Storage Tank and a Heat Pump Module, which
combine to make up the complete heat pump water heater.
The table below details the model numbers of the Storage Tanks and Heat Pump Modules
that comprise each model of heat pump water heater.
“xx” indicates the booster element capacity:
04 = 1.8kW
05 or 24 or 28 = 2.4kW
07 or 36 or 29 = 3.6kW
Brand
Model
Storage Tank
Heat Pump
Module
Rheem
551310xx
=
T551310xx
+
180532
Everhot
251310xx
=
T251310xx
+
180552
Solahart
310HAVxx
=
T310HAVxx
+
180533
Edwards
40467791xx
=
40467700xx
+
4000770009

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
SPECIFICATIONS
Storage Tank
Parameter
Model
551310
251310
310HAV
40467791
Capacity (Litres)
310
310
Boost Mode Capacity (Litres)
220
220
Limp Mode Capacity (Litres)
111
111
Booster Element Rating (kW)
1.8 / 2.4 / 3.6
2.4 / 3.6
T&PR Valve Rating (kPa)
1000
1000
Maximum Inlet Water
Pressure (kPa)
With ECV
680
680
Without ECV
800
800
Water Connections
Inlet / Outlet
Rp ¾” (20mm)
Rp ¾” (20mm)
Heat Pump
Rp ½” (15mm)
Rp ½” (15mm)
T&PR
Rp ½” (15mm)
Rp ½” (15mm)
Anode
Quantity
1
1
Length
1153
1153
Booster Element Controller Thermostat Setting
(Fixed)
62°C
62°C
Booster Element Mechanical Thermostat Setting
(Fixed)
70°C
70°C
Booster Element ECO Setting
88°C
88°C
Heat Pump Module
Parameter
180532 / 180552 / 180533 / 4000770009
Superheat Setting (Factory)
6K at 10ºC saturated suction temperature
Refrigerant Type / Charge
R134a / 1050 grams
Compressor Capacitor
35 µF +10/–5%, 370/440V AC, 50/60Hz
Compressor Current Draw
6.4A
Compressor Internal Overload
Setting (Automatic Reset)
Cut Out:
Cut In:
150°C
90°C
Compressor Winding Resistance
Run Winding –Red & Blue:
Start Winding –Red & Black:
2.2Ω at 20ºC
3.3Ω at 20ºC
High Pressure Switch1
Cut out: 2930kPa (+/- 100kPa)
Manual reset to close < 2240kPa (+/- 200kPa)
Fan Capacitor
2µF, 450V AC, 50/60Hz
Fan Winding Resistance
Run Winding –Black & Brown:
Start winding –Black & Blue:
184Ω at 20ºC
238Ω at 20ºC
Salmson Circulator Winding
Resistance
75.3Ω at 20ºC
Grundfos Circulator Winding
Resistance on Speed Setting 1
602Ω at 20ºC
Grundfos Circulator Capacitor
1.5µF +2/–5%
Grundfos Circulator Speed Setting
1
1HPS only applicable to models produced from 31/03/2016

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
PREVENTATIVE MAINTENANCE
It is suggested that the water heater be serviced annually, to retain optimum
performance.
Annual Service
Check for discharge from the T&PR valve. When the heat pump or element is
operating a small discharge of water may be evident. Operate the valve, easing the
lever to ensure the valve opens and reseats properly. Always open and close the
valve gently.
Check for leaks at all fittings.
Check for signs of excessive corrosion on the water heater and heat pump jackets.
Check for sludge build up and if necessary drain and flush tank.
Clear the circulator impellor & ensure free rotation.
Clean the condensate tray and check the condensate drain for blockages –clear if
necessary.
Clean blockages and debris from evaporator fins, fan blades, grilles and louvers.
Isolate power to the water heater and check all electrical connections for signs of
overheating due to poor connection.
Conduct an 'Electrical Insulation Test' on the water heater, refer to page 81.
Check for vibration or excess noise from the compressor, fan and circulator.
Check the refrigerant charge by inspecting the sight glass.
Visually check the unit for any potential problems.
Confirm correct heat pump module operation.
Five Year Service
Replace the T&PR valve.
Inspect and flush the expansion control valve (if fitted). If required, replace the valve.
Inspect and if required, replace the anode.
If the anode is not replaced, it should be replaced within three years of this service.
Check the heating element for excessive calcium build up or corrosion and replace if
necessary.
Check for leaks at all fittings.
Check for signs of excessive corrosion on the water heater and heat pump jackets.
Check for sludge build up and if necessary drain and flush tank.
Clear the circulator impellor & ensure free rotation.
Clean the condensate tray and check the condensate drain for blockages –clear if
necessary.
Clean blockages and debris from evaporator fins, fan blades, grilles and louvers.
Isolate power to the water heater and check all electrical connections for signs of
overheating due to poor connection.
Conduct an 'Electrical Insulation Test' on the water heater, refer to page 81.
Check for vibration or excess noise from the compressor, fan and circulator.
Check the refrigerant charge by inspecting the sight glass.
Visually check the unit for any potential problems.
Confirm correct heat pump module operation.

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
PRODUCT CHANGES
STORAGE TANK
Thermostat: Storage tanks manufactured from 14/08/2007 have an ST type thermostat in
place of the EWT type thermostat. The new ST thermostat is part number 052017, and the
storage tank wiring is revised to suit the new thermostat. The revised wiring diagram may
be found on page 34.
Double Sensor Strip: Storage tanks manufactured from 31/10/2007 have a double sensor
strip in place of the single sensor strip. Only one sensor strip is utilised for operation, the
second sensor strip is provided for redundancy in the event that the first sensor strip fails.
If the sensor strip in service fails and the spare sensor strip is plugged in, the plug must be
cut off the failed sensor strip so it is functionally and visibly disabled and can’t be
inadvertently re-used.
Sensor Strip Replacement Kit: An externally retrofittable sensor strip field kit is available,
for use in the event that both sensor strips have failed. The Sensor Strip Replacement Kit
is Rheem part number 299306.
Hot Water Return Diffuser: Storage tanks manufactured from 8/08/2013 have a diffuser
and new seal on the hot water return fitting. The diffuser and seal replace the short
dropper tube and dropper tube seal. The diffuser improves temperature stratification in the
storage tank.
Obsolete Models: Everhot, Solahart & Edwards branded models are no longer available.
Rheem branded product is compatible and is to be used if replacement is required.
HEAT PUMP MODULE
TX Valve: Heat pump modules manufactured from May 2007 have a TX valve with a brass
body. Heat pump modules manufactured prior to this time have a TX valve with a stainless
steel body. The superheat setting on both valve types is the same.
Automatic Air Eliminator: Heat pump modules manufactured from 14/05/2009 have an
automatic air eliminator installed between the outlet of the circulator and the heat
exchanger. The automatic air eliminator purges any potential air locks which may occur
upon initial installation or after servicing.
The Automatic Air Eliminator is also available in kit form, for retrofitting to models
manufactured prior to 14/05/2009. The Automatic Air Eliminator Kit is Rheem part number
290142.
NOTE: 310 Series Heat Pumps require a minimum supply water pressure of
200kPa to operate correctly. Fitment of this kit will NOT overcome operational
problems where the supply water pressure is not maintained at 200kPa or higher.
Vermin Shield Kit: A retrofittable vermin shield kit is available, for use in the event that
vermin are entering and damaging the heat pump module controller. The vermin shield is
fitted to controller chassis and works in conjunction with the controller cover. The Vermin
Shield Kit is Rheem part number 294008.
Service Valves: Heat pump modules manufactured from 2/02/2011 have suction and
discharge Schrader valves fitted to the refrigeration system.
Evaporator Sensor & Clip: Heat pump modules manufactured from 17/05/2011 have a
revised evaporator sensor and clip. The evaporator sensor is changed to Rheem part
number 056023 and has a dedicated clip, Rheem part number 056022. The new

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
evaporator sensor has the same temperature / resistance relationship as the other heat
pump module sensors.
Start Temperatures: Heat pump modules manufactured from 16/10/2012 have the
temperatures at which heat pump heating is started modified in the controller firmware.
The start heating temperatures have been changed from S3 < 50°C or S4 < 44.5°C, to S3
< 49°C or S4 < 43°C.
Grundfos Circulator and Heat Pump Module Upgrade: Heat pump modules
manufactured from 8/08/2013 (from serial number 2HP0000019) utilise a Grundfos
circulator and contain a number of design improvements. The full scope of changes
includes the following:
Grundfos circulator
Addition of water circuit check valve
Revised controller
oAddition of plugged fan connection
oRevised circulator connection
oRevised firmware
Addition of LED status codes
Addition of Freeze Protection Mode
Addition of compressor start delay
Revised circulator speed control algorithm
Revised controller cover
Addition of operating status LED panel
Revised heat exchanger water inlet and outlet sensors
Addition of protection to flexible hoses to prevent damage from rubbing
A retrofittable kit is available which allows existing installed heaters to be upgraded
to include the same improvements incorporated into models manufactured from
8/08/2013.
The kit, known as the Grundfos Circulator Kit is Rheem part number 290604.
NOTE:
The Grundfos circulator, controller and temperature sensors in the kit MUST
be fitted together. The kit comprises a system and requires that all of the
components are installed. The Grundfos circulator, controller and
temperature sensors are interdependent and failure to install all of the
components in the kit will result in malfunction of the water heater.
The Automatic Air Eliminator Kit (290142) must be fitted prior to fitting the
Grundfos Circulator Kit (290604).
Suction Line: Heat pump modules manufactured from 3/12/2013 (from serial number
1HP0003203) have a revised suction line.
Suction Line Brace: Heat pump modules manufactured from 1/04/2014 have a brace
added to the evaporator coil. The brace is mounted to the evaporator coil end plate and
the suction line is secured to the brace. The brace secures the suction line to prevent
excess movement, which may result in line breakage in the event of rapid power cycling to
the compressor due to the failure of an electronic component.
WARNING: The suction line brace MUST be fitted whenever the heat pump
is in operation.

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
Addition of High Pressure Switch: Heat pump modules manufactured from 31/03/2016
have a high pressure switch (HPS) fitted to provide additional high pressure protection.
The HPS is fitted in the liquid line between the condenser and the drier and will trip (open
circuit) in the event of an over-pressure situation. A trip of the high pressure switch will
result in the following:
Compressor ceases operation
Element heating enabled
Fan continues to operate
Pump continues to operate
Flashing red LED displayed (4 or 5 flashes depending on external conditions)
Green LED off
A tripped high pressure switch will be required to be manually reset before the heat pump
will attempt to resume normal operation. Until the HPS is reset the heater will operate in
element mode with fan and pump continually running during the heating cycle.
The existing HDi controller (part number 051728) is now
obsolete and is replaced with a revised HDi controller (part
number 051738) which has an additional plug jack to
accommodate the HPS. This revised controller can be used
on all HDi models, including earlier models that do not have a
HPS fitted. A HPS bypass plug (part number 051733) has
been developed for use on earlier models that do not have
HPS fitted.
A service kit (part number 299279) consisting of a HPS
bypass plug, replacement HDi controller and an instruction
sheet is available from Spare Parts.
The Grundfos Circulator Retrofit Kit (part number 290604) is
also modified to include this revised HDi controller and HPS
bypass plug.
Obsolete Models: Everhot, Solahart & Edwards branded modules are no longer available.
Rheem branded product is compatible and is to be used if replacement is required.
REFRIGERATION TERMS AND THEIR MEANING
Condense –The action of a substance as it releases heat and changes state from a
vapour (gas) to a liquid.
Evaporate –The action of a substance as it absorbs heat and changes state from a liquid
to a vapour (gas).
Heat of Compression –The heat energy added to a substance by the act of compressing
it.
High Side –Components and pipework of a refrigeration system operating at high
pressure, generally the compressor case where a rotary compressor is utilised, discharge
line, condenser, liquid line, liquid receiver where utilised and filter drier.
HIGH PRESSURE
SWITCH JACK
Bypass
Plug

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
Latent Heat –The ‘hidden’ heat energy that causes a change in state of a substance,
without changing its temperature.
Low Side –Components and pipework of a refrigeration system operating at low
pressure, generally the evaporator, suction line and suction accumulator.
Saturated Liquid –A liquid at the point that it will boil with any increase in temperature, at
a given pressure.
Saturated Vapour –A vapour at the point that it will condense with any decrease in
temperature, at a given pressure.
Subcooled Liquid –A liquid at a temperature below its saturation point, at a given
pressure.
Superheated Vapour –A vapour (gas) at a temperature above its saturation point, at a
given pressure.
COMPONENTS AND THEIR FUNCTION
Anode (Sacrificial) –A metal alloy electrode installed in the water heater cylinder that
protects the cylinder from corrosion by galvanic action.
Compressor –An electromechanical device that increases the pressure of superheated
refrigerant vapour by decreasing its volume, as well as increasing its temperature due to
the addition of the heat of compression. The increase in pressure causes the refrigerant to
circulate through the refrigeration system.
Condenser –A heat exchanger containing three chambers; one for the refrigerant, one for
water and a third separating chamber which is open to atmosphere. The refrigerant enters
the condenser as a high pressure, high temperature superheated refrigerant vapour and
gives off its heat. This heat is absorbed by the water from the storage tank which is being
circulated through the water chamber in the condenser. As the refrigerant gives off its heat
and becomes cooler, it condenses (changes state) to a saturated liquid. Cooling of the
saturated liquid refrigerant continues such that it becomes subcooled.
Diffuser –A plastic device installed in the cold water inlet of the water heater cylinder to
assist with stratification. It also acts as a fitting liner.
Evaporator –An aluminium finned copper coil where the low pressure, low temperature
refrigerant absorbs heat from the surrounding ambient air. As the refrigerant absorbs heat
and becomes warmer, it evaporates (changes state) to a saturated vapour. Heating of the
saturated refrigerant vapour continues such that it becomes superheated.
Fitting Liner –A plastic tube installed in the cold water inlet of the storage tank to provide
protection against corrosion through the life of the water heater.
Heating Element –A tubular device containing a resistive element, that converts electrical
energy to heat.

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
High Pressure Switch: An electromechanical device with a set of normally closed
contacts that will open circuit when the detected refrigeration system pressure rises above
a predetermined value. The contacts can be manually reset once the refrigeration system
pressure falls below a predetermined value.
Outlet Delivery Tube (Dip Tube) –A plastic tube installed in the hot water outlet of the
water heater cylinder to conduct water from the highest point to the outlet connection. It
also acts as a fitting liner.
Pressure Limiting Valve (PLV) –A valve that controls its outlet pressure to a
predetermined limit.
Receiver / Filter Drier –A device fitted in the refrigerant liquid line. The filter drier
component traps impurities and removes moisture from the sealed refrigeration system.
The receiver component stores liquid refrigerant.
Sensor –A device which changes resistance with a change in temperature, also known as
a thermistor. Sensors are used to measure temperature and feed the information back to a
control system.
Sensor Strip –A sensor device containing multiple temperature sensors.
Suction Accumulator –A device fitted in the refrigerant suction line, which accumulates
and prevents any liquid refrigerant from entering and damaging the compressor. Any liquid
refrigerant in the suction accumulator is evaporated or “boiled off” to a vapour.
Temperature and Pressure Relief (T&PR) Valve –A valve designed to provide
automatic relief by discharging water in case of excessive temperature, pressure or both.
Never fit a T&PR Valve with a pressure rating greater than that indicated on
the product rating label.
Thermal Cut Out (ECO) –A manually reset temperature sensitive device mounted
against the water heater cylinder, which cuts off the supply of electrical energy.
Thermostat –A temperature sensitive device mounted against the water heater cylinder,
which controls the supply of electrical energy to maintain the stored water at the required
temperature.
Thermostatic Expansion (TX) Valve –A mechanical valve that expands the liquid
refrigerant to a lower pressure as it moves through the TX valve’s orifice. The expansion
process also lowers the temperature of the refrigerant, to a point below that of the
surrounding ambient air. The TX valve has a bulb that senses the temperature of the
suction line at the evaporator outlet. The TX valve thermostatically meters the flow of
expanding refrigerant to the evaporator, in response to the temperature of the suction line
as measured by the bulb.

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
CONTROLLER
The 310 Series Heat Pump has an electronic controller in the heat pump module. Power
and temperature sensor connections are made at the controller.
Power and Sensor Strip Connections
Models Manufactured from 31/03/2016 (or
with Grundfos retrofit kit fitted from 04/16)
Models Manufactured 8/08/2013 –30/03/16 (or
with Grundfos retrofit kit fitted up to 03/16)
Models Manufactured prior to 8/08/2013 (Salmson Circulator)
TANK SENSOR
CABLE PLUG
IN POSITION
POWER
CABLE
CABLE
TIE
BACKUP
PLUG
HIGH PRESSURE
SWITCH JACK
BACKUP
PLUG
TANK SENSOR
CABLE PLUG
IN POSITION
POWER
CABLE
POWER
CABLE
POWER
CONNECTOR
POWER
CONNECTOR
IN POSITION
CABLE
TIE
BACKUP
PLUG
CABLE
TIE
TANK SENSOR
CABLE PLUG
TANK SENSOR
CABLE
TANK SENSOR
CABLE PLUG
TANK SENSOR
CABLE
BACKUP
PLUG
CONTROL BOARD HEAT PUMP with
SENSOR CABLE
POWER CABLE
CONNECTION
SENSOR STRIP
CONNECTION
SENSOR STRIP
CABLE PLUG
SENSOR STRIP CABLE

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
Printed Circuit Board (PCB)
The main features of the controller’s printed circuit
board (PCB) are shown on the diagram opposite.
The connection marked “Relay Control” energises or
de-energises a relay that switches from heat pump
heating to electric element heating.
The “Compressor TRIAC” switches the power to the
compressor on and off.
The green and red LED’s display information about
the heat pump’s operating status and / or fault
conditions –see the LED Status Codes section on
page 24.
Models manufactured prior to 8/08/2013 have LED’s
mounted on the printed circuit board.
Models manufactured from 8/08/2013 or with a
Grundfos Circulator Kit installed have an external
LED panel that plugs into the printed circuit board at
the location noted “LEDs” in the diagram.
These models (manufactured from 8/08/2013 or with a Grundfos Circulator Kit installed)
utilise additional functionality and detailed Fault Codes –see the LED Status Codes
section on page 24.
Sensor Strip
A sensor strip containing 6 temperature sensors is located inside the
storage tank. The sensor strip is inside the storage tank’s insulation, located
on the outside wall of the storage tank’s internal cylinder.
The sensors on the sensor strip are numbered S0 –S5, from the top to the
bottom.
The sensor strip is monitored by the controller and provides information on
the temperature of the water over the height of the storage tank. This
information is utilised to determine heater operation.
For more information on the sensor strip refer to the Sensor Strip Testing
section on page 70.
Relay
Control
S0
S1
S2
S3
S4
S5

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
Sensors
Five independent temperature sensors (thermistors) are
utilised in the heat pump module.
The sensors are identified as follows:
Heat exchanger (HX) water outlet (T0)
Heat exchanger (HX) water inlet (T1)
Evaporator (T2)
Compressor (T3)
Ambient (T4)
The sensors are monitored by the controller and provide information on specific
temperatures in the heat pump module. This information is utilised to determine heater
operation.
For more information on the sensors refer to the Sensor Testing section on page 71.
AUTOMATIC AIR ELIMINATOR
In order for the automatic air eliminator to function correctly, the following steps must be
taken:
1. Open the air bleed valve screw by rotating anticlockwise one turn.
2. This will allow air to bleed from the heat pump module’s water circuit during filling of
the tank.
3. Leave the air bleed valve screw in this position.
4. Ensure the screw is not removed, nor left screwed shut.
Models Manufactured prior to 8/08/2013
(Salmson Circulator)
Models Manufactured from 8/08/2013
or with a Grundfos Circulator Kit Installed
INSULATION
ROTATE AIR BLEED VALVE
SCREW ONE TURN
ANTICLOCKWISE

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
OPERATION
The heat pump utilises a form of heating called “top down”heating.
This means that heated water from the heat pump is returned to the
top of the storage tank, meaning the water at the top of the tank is
always at a usable temperature.
The controller varies the speed of the circulator (1), so that the
temperature of the water leaving the heat exchanger is always
maintained at a usable temperature.
The circulator (1) draws cold water from the bottom of the storage tank
via the long dropper tube (2). The water passes through the heat
exchanger (3), also known as the condenser, where it is heated by the
refrigerant. The water is then returned to the top of the storage tank
via the short dropper tube (4).
The controller contains a main relay that ensures power can only be delivered to the
refrigeration compressor or the booster element. The main relay will enable element
operation in its un-powered (off) state. A manual reset high pressure switch is wired in
series to the main relay and will de-energise the relay in the event of a refrigerant over-
pressure situation.
Whenever power is available and with no faults present, the controller energises the main
relay to enable compressor operation. Power for the compressor is then passed through
an electronic switch called a triac, which is downstream of the relay and allows the
controller to switch the compressor on and off in response to the demand for heat pump
heating.
The 310 Series Heat Pump water heaters utilise R134a refrigerant to
transfer heat from the atmosphere to the water in the storage tank.
The four main components of the sealed refrigeration system are the
compressor (6), condenser (heat exchanger) (3), thermostatic
expansion (TX) valve (7), and the evaporator (5).
Refrigerant enters the compressor as a low pressure superheated vapour. The
compressor increases the pressure of the refrigerant vapour by decreasing its volume, as
well as increasing its temperature due to the addition of the heat of compression.
The high pressure, high temperature superheated refrigerant vapour flows to the
condenser (heat exchanger), where it gives off its heat. This heat is absorbed by the water
from the storage tank which is being circulated through a separate chamber in the
condenser. As the refrigerant gives off its heat and becomes cooler, it condenses
(changes state) to a saturated liquid. Cooling of the saturated liquid refrigerant continues
such that it becomes subcooled, meaning it is cooled to a temperature below its saturation
point.
7

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
The liquid refrigerant then moves through the thermostatic expansion (TX) valve, where it
is expanded to a lower pressure by moving through the TX valve’s orifice. The expansion
process also lowers the temperature of the refrigerant, to a point below that of the
surrounding ambient air.
The TX valve has a bulb that senses the temperature of the suction line at the evaporator
outlet. The TX valve thermostatically meters the flow of expanding refrigerant in response
to the temperature of the suction line.
Following expansion, the low pressure, low temperature refrigerant moves into the
evaporator where it absorbs heat from the surrounding ambient air. As the refrigerant
absorbs heat and becomes warmer, it evaporates (changes state) to a saturated vapour.
Heating of the saturated refrigerant vapour continues such that it becomes superheated,
meaning it is heated to a temperature above its saturation point. This low pressure
superheated vapour then returns to the compressor to complete the cycle.
STANDBY MODE
Standby is an idle mode where power is available, but water heating is not required.
All faults are cleared from the controller whenever the system is in Standby Mode,
however the system continues to check for new faults. In models manufactured from
8/08/2013 or with a Grundfos Circulator Kit installed, the Insufficient Water Flow Rate
Warning is not cleared during Standby Mode –see the Heat Pump Heating section on
page 18 for further explanation of this warning.
Models Manufactured from 8/08/2013 or with a Grundfos Circulator Kit Installed
Whilst in Standby Mode, if the compressor temperature is less than 60°C, the green
LED is on solid. If the compressor temperature is greater than or equal to 60°C, the
green LED will display one flash.
If the Insufficient Water Flow Rate Warning is current, the green LED is on solid and
the red LED will display one flash. This warning is only displayed during Standby
Mode and does not inhibit operation or any function –see the Heat Pump Heating
section on page 18 for further explanation of this warning.
A Freeze Protection function is utilised in Standby Mode, in order to prevent the
water within the heat pump module freezing during low ambient conditions. (Only
models manufactured from 8/08/2013 or with a Grundfos Circulator Kit installed are
susceptible to freezing in the water circuit, due to the presence of a check valve.)
During Standby Mode, if either the heat exchanger water outlet temperature or the heat
exchanger water inlet temperature fall below 3°C, the circulator is switched on at full speed
in order to circulate heated water from the storage tank through the water circuit, to
prevent freezing. The circulator remains on for at least 30 seconds and will switch off when
the heat exchanger water outlet temperature and the heat exchanger water inlet
temperature have both risen above 5°C. The circulator will also switch off if the system
detects that heat pump heating is required, at which point the system will go to Heat Pump
Mode.
Models Manufactured prior to 8/08/2013 (Salmson Circulator)
Whist in Standby Mode, the green LED is illuminated and remains on.

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
HEAT PUMP MODE
Models Manufactured from 8/08/2013 or with a Grundfos Circulator Kit Installed
Heat pump heating is initiated under the following conditions, as determined by the sensor
strip: S3 detects a temperature less than 49°C or S4 detects a temperature less than
43°C.
Heat Pump Mode consists of three stages –System Check, Circulator Pre-Run and Heat
Pump Heating.
System Check
During system check, the green LED will display one flash.
If the compressor sensor detects a temperature greater than 60°C, the system will
remain in Standby Mode until the compressor has cooled.
The controller checks that the 5 minute start delay has elapsed. The start delay may
have already elapsed, as it begins from the last compressor shut down. To begin
the start delay, the control system requires that power is available. The start delay
does not occur when power is applied to a new system for the first time. The 5
minute start delay cannot be bypassed or cancelled.
Once the compressor has cooled and the start delay has elapsed, the system goes
to Circulator Pre-Run.
Circulator Pre-Run
During Circulator Pre-Run, the green LED will display 2 flashes.
The circulator will commence operation at full speed for a period of 30 seconds.
Heat Pump Heating
During Heat Pump Heating, the green LED will display 4 flashes.
After the Circulator Pre-Run, the compressor and evaporator fan also commence
operation and heat pump heating commences.
When the compressor and evaporator fan commence operation, the controller
begins to vary the circulator speed by pulsing the circulator’s power supply, to
control the heat exchanger water outlet temperature to 62°C.
This means that 62°C water is delivered to the top of the storage tank for the remainder
of the heat pump operational cycle.
Heat Pump Heating ceases and the system returns to Standby Mode under the
following conditions, as determined by the sensor strip:
S4 detects a temperature greater than 53°C or S5 detects a temperature
greater than 50°C.
After 4 minutes in Heat Pump Heating, the controller constantly monitors the
circulator speed and heat exchanger water outlet temperature, looking for specific
conditions that suggest the circulator is unable to provide a sufficient water flow
rate.
If the controller detects that the circulator is running at full speed and the heat
exchanger water outlet temperature is greater than 65°C, the controller initiates the
Insufficient Water Flow Rate Warning.

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
When the Insufficient Water Flow Rate Warning is raised, Heat Pump Heating will
stop irrespective of the tank water temperature as determined by the sensor strip
and the system will return to Standby Mode.
The warning does not inhibit operation or any function.
The Insufficient Water Flow Rate Warning is automatically cleared from the
controller whenever the heat pump successfully completes a full cycle in Heat
Pump Mode without detecting the conditions that generate the Insufficient Water
Flow Rate Warning. There is no other way to clear the Insufficient Water Flow Rate
Warning.
Models Manufactured prior to 8/08/2013 (Salmson Circulator)
During Heat Pump Heating, the green LED flashes.
Heat pump heating is initiated under the following conditions, as determined by the sensor
strip:
Models Manufactured prior to 16/10/2012
S3 detects a temperature less than 50°C or S4 detects a temperature less than
44.5°C.
Models Manufactured from 16/10/2012
S3 detects a temperature less than 49°C or S4 detects a temperature less than
43°C.
Once heat pump heating is initiated:
If the compressor sensor detects a temperature greater than 60°C, the system will
remain in Standby Mode until the compressor has cooled.
The circulator will commence operation at full speed for a period of 30 seconds.
After the 30 second circulator operation, the compressor and evaporator fan also
commence operation and heat pump heating commences.
When the compressor and evaporator fan commence operation, the circulator drops to
its lowest speed to allow the refrigeration system to reach operating temperature as
quickly as possible.
When the heat exchanger water outlet sensor detects a temperature greater than or
equal to 59°C, the refrigeration system has reached operating temperature.
At this point, the controller begins to vary the circulator speed by pulsing the circulator’s
power supply, to control the heat exchanger water outlet temperature to 62°C.
This means that 62°C water is delivered to the top of the storage tank for the remainder
of the heat pump operational cycle.
Heat pump heating ceases and the system returns to Standby Mode under the
following conditions, as determined by the sensor strip:
S4 detects a temperature greater than 53°C or S5 detects a temperature
greater than 50°C.

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TM025: 310 Series Heat Pump Service Instructions
Rev AF: Issued March 2016
ELEMENT MODE
At all times when power is available, the controller monitors the condition of the heat pump
system. Should the ambient temperature be too low for heat pump operation or a fault is
detected, the controller exits Heat Pump Mode and initiates Element Mode.
In models manufactured from 8/08/2013 or with a Grundfos Circulator Kit installed, the
LED’s will display a fault code during Element Mode.
In models manufactured prior to 8/08/2013 (Salmson circulator), the red LED flashes
during Element Mode.
Boost Mode
Models Manufactured from 8/08/2013 or with a Grundfos Circulator Kit Installed
If S0 or S1 on the sensor strip is functional, Element Mode will utilise Boost Mode. If both
S0 and S1 are functional the controller will use S1, otherwise it will use whichever of the
two sensors is functional.
When Element Mode utilises Boost Mode, the controller continues to use the circulator to
control the temperature of the water in the storage tank, however the main relay is de-
energised thereby supplying power to the element.
During Boost Mode, the element operates instead of the heat pump and the controller
uses the sensor strip to continue to drive top down heating. The element heats the water
until the temperature of the water detected by S0 or S1 is greater than 62°C. The controller
will then operate the circulator, thereby bringing cold water from the bottom of the storage
tank to the top of the storage tank. The circulator continues to operate until the
temperature of the water detected by S0 or S1 is less than 61°C. At this point the controller
switches the circulator off and the element continues heating the water until again the
temperature of the water detected by S0 or S1 is greater than 62°C.
This process continues until the temperature of the water detected by S4 is greater than
53°C, or the temperature of the water detected by S5 is greater than 50°C. At this point the
controller re-energises the main relay, thereby switching the element off.
The system returns to Standby Mode, the green LED is illuminated and remains on, the
fault is cleared and normal operation is resumed when heating is next required.
If Element Mode is in use due to the ambient sensor detecting a temperature of less than
0°C, normal heat pump operation will resume when the ambient sensor detects a
temperature above 2°C.
If Element Mode is in use due to the evaporator sensor detecting a temperature of less
than -3°C, normal heat pump operation will resume when the evaporator sensor detects a
temperature above 2°C.
Note: If S4 on the sensor strip has failed, the system will still operate in Boost Mode,
unless S3 or S5 have also failed. If S4 and S3 have both failed, or S4 and S5 have both
failed, Element Mode will utilise Limp Mode.