Rheem MPi 551 Series Technical Document

This water heater must be installed and serviced by a qualified person.
Please leave this guide with the householder.
Owner’s Guide
and
Installation Instructions
Air Sourced Heat Pump
Water Heater
MPi 551 Series

PATENTS
This water heater may be protected by one or more patents or registered designs in the name of
Rheem Australia Pty Ltd.
TRADE MARKS
®Registered trademark of Rheem Australia Pty Ltd.
™ Trademark of Rheem Australia Pty Ltd.
Note: Every care has been taken to ensure accuracy in preparation of this publication.
No liability can be accepted for any consequences, which may arise as a result of its application.

3
CONTENTS
HOUSEHOLDER –We recommend you read pages 4 to 18.
The other pages are intended for the installer but may be of interest.
About Your Water Heater............................................................................................................ 4
Regular Care .............................................................................................................................. 10
Water Supplies........................................................................................................................... 12
Save A Service Call................................................................................................................... 14
Installation.................................................................................................................................. 19
Heat Pump And Tank Assembly .............................................................................................. 25
Connections –Plumbing .......................................................................................................... 37
Connections –Electrical........................................................................................................... 39
Commissioning.......................................................................................................................... 41
Draining The Water Heater ....................................................................................................... 44
Warranty..................................................................................................................................... 47

4
ABOUT YOUR WATER HEATER
WATER HEATER APPLICATION
This water heater is designed for use in a single family domestic dwelling for the purpose of heating potable
water. Its use in an application other than this may shorten its life.
MODEL TYPE
Your Rheem®air sourced heat pump water heater is designed for outdoor installation only. The model you
have chosen is a 551 series model. The 551 325 model water heater is recommended for connection to a
minimum 16 hour per day power supply. The 551 410 model water heater is recommended for connection to
a 24 hour per day power supply.
A Rheem heat pump water heater consumes less energy than an electric water heater. The impact on an
electricity bill will depend on the tariff arrangement of the water heater replaced and where you live. Contact
your energy provider for more information on tariff arrangements and cost comparisons.
The Rheem air sourced heat pump water heater has a Rheemglas®vitreous enamel lined steel cylinder. The
water heater‟s evaporator absorbs heat from the surrounding air and transfers this heat into the water.
When hot water is drawn off and cold water enters the tank, the thermostat
activates a fan, a compressor and a circulator. The fan draws outside air in
through the air inlet louvres at the side of the heat pump module and the
pump circulates water from the bottom of the storage tank through a heat
exchanger. Heat is absorbed from the air by an evaporator and transferred
into the water through the heat exchanger. The resulting cold air is then
discharged through the air outlet grille back to atmosphere and the heated
water is circulated back into the storage tank. This process continues while
heating is required until the water in the storage tank reaches a
temperature of 60°C.
Even on cloudy or cold days, heat is drawn from the surrounding air. The
heat pump will operate when the ambient air temperature is between a
minimum of 3°C to 5°C and maximum of 45°C to 55°C. The booster
heating unit will operate when the ambient air temperature is outside of this
temperature range if heating is required. The efficiency of the water heater
increases as the ambient air temperature increases within the operating
range of the heat pump.
Automatic safety controls are fitted to the water heater to provide safe and efficient operation.
ELECTRIC BOOSTING
Ice may begin to form on the evaporator reducing the heat pump efficiency, when the ambient air
temperature falls below 7°C and the heat pump has been operating for an extended period. At ambient air
temperatures below 3°C to 5°C, the water heater deactivates the heat pump operation and switches to the
booster heating unit. During this period the evaporator will defrost if necessary.
At ambient air temperatures above 45°C to 55°C, the water heater deactivates the heat pump operation and
switches to the booster heating unit.
The water inside the tank will be heated to a temperature of 70°C by the electric booster heating unit if
heating is required. The temperature setting of the thermostat controlling the booster heating unit is not
adjustable and is set at 70°C.
Boost Capacity
Element size
551 325
551 410
2.4 kW*, 3.6 kW*
180 litres
200 litres
1.8 kW
100 litres
-
* The boost capacity of a 2.4 kW or 3.6 kW low watts density heating
unit if used is 100 litres (551 325) or 125 litres (551 410).

ABOUT YOUR WATER HEATER
5
FREEZE PROTECTION
The water heater has a freeze protection system. The freeze protection system will protect the water heater
from damage, by preventing ice forming in the waterways of the water heater, in the event of freezing
conditions occurring.
If the ambient air temperature falls below 1°C and the heat pump is not operating, the system will operate the
circulator periodically. During this freeze protection cycle, the circulator will operate for thirty (30) seconds
and then rest for fifteen (15) minutes, before the cycle is recommenced. Water is circulated from the storage
tank through the heat pump circuit, to prevent freezing in the connecting pipe work and heat pump module.
The green LED will flash a series of four (4) flashes whilst the circulator is operating.
The water heater has NO WARRANTY for freeze damage if power is unavailable at the water heater.
Warning: In areas where the ambient air temperature may fall below 1°C, power must be available to the
water heater at all times to prevent freezing in the heat pump circuit.
HOW HOT SHOULD THE WATER BE?
The system controls (compressor, evaporator and fan) will
operate until a water temperature of 60°C is reached. If the
ambient air temperature is outside of the heat pump‟s operating
range, the water temperature is boosted automatically to 70°C
by the thermostatically controlled booster electric heating unit, if
heating is required.
To meet the requirements of the National Plumbing Standard
the temperature of the stored water must not be below 60°C.
HOTTER WATER INCREASES THE RISK OF SCALD INJURY
This water heater can deliver water at temperatures which can
cause scalding. Check the water temperature before use, such
as when entering a shower or filling a bath or basin, to ensure it
is suitable for the application and will not cause scald injury.
We recommend and it may also be required by regulations that
an approved temperature limiting device be fitted into the hot
water pipe work to the bathroom and ensuite when this water
heater is installed. This will keep the water temperature below
50°C at the bathroom and ensuite. The risk of scald injury will
be reduced and still allow hotter water to the kitchen and
laundry.
TEMPERATURE ADJUSTMENT
The thermostats controlling the heat pump and the booster heating unit are factory set and not adjustable.
WARNING
This water heater is only intended to be operated by persons who have the experience or the knowledge and
the capabilities to do so. This water heater is not intended to be operated by persons with reduced physical,
sensory or mental capabilities i.e. the infirm, or by children. Children should be supervised to ensure they do
not interfere with the water heater.
This water heater uses 240 V AC electrical power for operation of the control systems and the electrically
operated components. The removal of the access cover(s) will expose 240 volt wiring. They must only be
removed by a qualified person.
Do not use aerosols, stain removers and household chemicals near the water heater whilst it is
working. Gases from some aerosol sprays, stain removers and household chemicals are corrosive to the
materials used in the heat pump system.
Do not store swimming pool chemicals, household cleaners, etc., near the water heater.
Ensure the air flow, air inlet louvres and outlet grille are not obstructed in any way at any time.
typical maximum temperature
from heat pump operation,
minimum recommended stored
water temperature
maximum recommended supply
temperature to bathrooms and
ensuites
booster temperature setting

ABOUT YOUR WATER HEATER
6
SAFETY
This water heater is supplied with a thermostat, two over-temperature energy cut-outs and a combination
temperature pressure relief valve. These devices must not be tampered with or removed. The water heater
must not be operated unless each of these devices is fitted and is in working order.
The operation of the over-temperature cut-out on the thermostat indicates a possibly dangerous situation. If
the over-temperature cut-out operates, it must not be reset and the water heater must be serviced by a
qualified person.
If the electrical supply conduit to the water heater is damaged, it must be replaced by a qualified person in
order to avoid a hazard. Phone Rheem Service or their nearest Accredited Service Agent to arrange for an
inspection.
Warning: For continued safety of this water heater it must be installed, operated and maintained in
accordance with the Owner‟s Guide and Installation Instructions.
The Rheem warranty may not cover faults if relief valves or other safety devices are tampered with or
if the installation is not in accordance with these instructions.
MAINS PRESSURE
The water heater is designed to operate at mains pressure by connecting directly to the mains water supply.
If the mains supply pressure in your area exceeds that shown on page 21, a pressure limiting valve must be
fitted. The supply pressure should be greater than 350 kPa for true mains pressure operation to be achieved.
A minimum water supply pressure of 200 kPa is required to enable the heat pump circulator and heat pump
system to operate effectively.
OPERATING MODE MONITOR
An operating mode monitor is located on the front of the heat pump module and houses a green and a red
LED.
The green LED, marked “NORMAL”, indicates the current operating mode of the heat pump water heater
and the red LED, marked “ATTENTION”, indicates a fault mode.
The green LED will emit either a constant glow or a series of flashes, with a 2 second interval between each
series. A series of long green flashes may also be emitted.
The red LED will emit a series of flashes, with a
2 second interval between each series, only if there
is a particular fault condition with the system.
The modes are:
Green LED
Red LED
Operational Modes
solid green
(remains on)
off
Standby mode –water is hot
1 x green
off
Call for heating received –system checks performed
Note: unit may wait and continue flashing until compressor has cooled from its
last operation
2 x green
off
Heat pump preheating
3 x green
off
Heat pump operation –compressor and fan running
4 x green
off
Freeze protection operation –circulator on
long green
off
Heating unit on –
ambient air temperature below 3°C to 5°C or above 45°C to 55°C
rapid green
off
System start up –heating unit on
no green
(remains off)
off
No power at the water heater or to the heat pump or a possible fault condition
Refer to notes overleaf before calling for service

ABOUT YOUR WATER HEATER
7
Notes:
Power must be available at the water heater and to the heat pump for the LEDs to glow or flash.
Time controlled power supply (power must be available at the water heater)
If the water heater is connected to a time controlled power supply, then during periods of no power
supply at the water heater the LEDs will be off.
This is not a fault condition, but a result of no power being available to energise the LEDs.
The green LED will recommence glowing or flashing when power is available again at the water heater.
Heat pump operating range (power must be available to the heat pump)
The heat pump‟s operating range is between an ambient air temperature of a minimum of 3°C to 5°C
and a maximum of 45°C to 55°C. The heat pump will not operate when the ambient air temperature is
outside the heat pump‟s operating range.
If heating is required, the water heater will commence heating with the booster heating unit in booster
heating mode (long green flash) instead. The water will be heated to 70°C during these periods.
At the completion of this heating cycle by the booster heating unit (long green flash), the thermostat
controlling the booster heating unit opens circuit cutting power to the heat pump causing the green LED
to go out. This is not a fault condition, but a result of the power being cut to the heat pump by the
thermostat.
Refer to “Heat pump operating range” on page 15 in the “Save A Service Call” section of this Owner‟s
Guide for further explanation.
Possible fault condition –Green LED is off or red LED is flashing
If there is power to the water heater and the green LED is off or the red LED is flashing, this indicates
there may be a fault condition with the water heater. The red LED may emit up to nine flashes in each
series of flashes.
There may be a fault condition with the water heater if either:
there is power available at the water heater and the green LED is off, and
the water heater has not operated outside of the heat pump‟s operating range – refer to “Heat
pump operating range” on page 15.
Before phoning to arrange a service inspection due to the green LED being off, refer to “Heat Pump
Is Not Operating” on page 15 in the “Save A Service Call” section of this Owner‟s Guide.
or
the red LED is flashing –the red LED may emit up to nine flashes in each series of flashes
The fault condition which led to the red LED flashing may be cleared after the backup heating cycle
by the booster heating unit has completed. When heating is next required the red LED will
recommence to flash the fault code for 27 seconds and then extinguish. If the red LED then
recommences to flash or recommences to flash after the heat pump next operates, a service call
may be required.
Before phoning to arrange a service inspection due to the red LED flashing, refer to “Heat Pump Is
Not Operating” on page 15 in the “Save A Service Call” section of this Owner‟s Guide.
TIMER CONTROL
A timer can be installed in the electrical circuit to the water heater. The timer must be weatherproof if it is
installed outdoors.
It may be desirable for the water heater not to operate between certain hours, such as during the peak
period when connected to a Time of Use electricity supply due to a more expensive tariff rate applying.
A timer will affect the operating times of both the heat pump circuit and the booster heating unit.
Note: The 551 325 model water heater is recommended for connection to a minimum 16 hour per day power
supply. The 551 410 model water heater is recommended for connection to a 24 hour per day power supply.

ABOUT YOUR WATER HEATER
8
TO TURN OFF THE WATER HEATER
If you plan to be away from home for only a few nights, we suggest you leave the water heater switched on.
If it is necessary to turn off the water heater:
Switch off the electrical supply at the isolating switch to the water heater.
Close the cold water isolation valve at the inlet to the water heater.
Note: If there is a risk of freezing conditions, the electrical supply to the water heater should not be switched
off, otherwise damage could result (refer to “Freeze Protection” on page 5).
TO TURN ON THE WATER HEATER
Open the cold water isolation valve fully on the cold water line to the water heater.
Switch on the electrical supply at the isolating switch to the water heater.
Check and if required reset the timer, if one is installed.
When power is turned on or reconnected to the water heater, the green LED will flash rapidly for three (3)
seconds. The LED display will then return to the current operational status.
The water heater may take up to forty five minutes to commence operating when the power supply is
switched on. The heat pump will only operate when power is available at the water heater, the water in the
storage tank requires heating, the heat pump compressor is cool and the ambient air temperature is within
the heat pump‟s operating temperature range of between a minimum of 3°C to 5°C and a maximum of 45°C
to 55°C. If the ambient temperature is outside of this range, the water heater will commence heating with the
booster heating unit.
When the heat pump is operating, the system will switch to the booster heating unit if the detected ambient
air temperature is outside the operating temperature range of between a minimum of 3°C to 5°C and a
maximum of 45°C to 55°C.
The system will not switch back to heat pump operation from the booster heating unit if the detected ambient
air temperature has moved back within the heat pump‟s operating temperature range. The heating cycle will
be completed by the booster heating unit.
Note: The heat pump may not turn on immediately after either having just completed a heating cycle and
more hot water is drawn from the water heater or power is shut down to the compressor, either during or at
the end of a heating cycle. The heat pump will wait until the compressor has cooled down and the conditions
for start up are favourable in order to protect the compressor from damage. This will be a minimum of forty
five (45) minutes and may take up to ninety (90) minutes from the last heating cycle.
GOING ON HOLIDAYS
If you plan to be away from home for a few nights, we suggest you leave the water heater switched on. If you
plan to be away for a longer period, conserve energy by switching off the isolating switch to the water heater.
It is not advised to switch off the water heater if there is the risk of freeze conditions. Refer to “To Turn Off
The Water Heater” on page 8.
PRECAUTIONS
Where damage to property can occur in the event of the water heater leaking, the water heater must be
installed in a safe tray. Construction, installation and draining of a safe tray must comply with AS/NZS 3500.4
and all local codes and regulatory authority requirements.
The water heater must be maintained in accordance with the Owner‟s Guide and Installation Instructions.
Refer to “Regular Care” on page 10 and to “Anode Inspection and Replacement” on page 12.
If this water heater is to be used where an uninterrupted hot water supply is necessary for your application or
business you should ensure that you have back up redundancy within the hot water system design. This
should ensure the continuity of hot water supply in the event that this water heater were to become
inoperable for any reason. We recommend you seek advice from your plumber or specifier about your needs
and building back up redundancy into your hot water supply system.

ABOUT YOUR WATER HEATER
9
HOW DO I KNOW IF THE WATER HEATER IS INSTALLED CORRECTLY?
Installation requirements are shown on pages 19 to 23. The water heater must be installed:
by a qualified person, and
in accordance with the installation instructions, and
in compliance with Standards AS/NZS 3500.4, AS/NZS 3000 and all local codes and regulatory authority
requirements.
In New Zealand, the installation must also conform with Clause G12 of the New Zealand Building Code.
VICTORIAN CUSTOMERS
Notice to Victorian Customers from the Victorian Plumbing Industry Commission. This water heater must be
installed by a licensed person as required by the Victorian Building Act 1993.
Only a licensed person will give you a Compliance Certificate, showing that the work complies with all the
relevant Standards. Only a licensed person will have insurance protecting their workmanship for 6 years.
Make sure you use a licensed person to install this water heater and ask for your Compliance Certificate.
DOES THE WATER CHEMISTRY AFFECT THE WATER HEATER?
The water heater is suitable for most public water supplies, however some water chemistries may have
detrimental effects on the water heater, its components and fittings. Refer to “Water Supplies” on page 12.
If you are in a known harsh water area or you are not sure of your water chemistry, have your water checked
against the conditions described on pages 12 to 13.
HOW LONG WILL THE WATER HEATER LAST?
The water heater is supported by a manufacturer‟s warranty (refer to page 47). There are a number of
factors that will affect the length of service the water heater will provide. These include but are not limited to
the water chemistry, the water pressure, the water temperature (inlet and outlet) and the water usage
pattern. Refer to “Precautions” on page 8.
ENVIRONMENT
At the end of the service life of the heat pump water heater and prior to the water heater being disposed of, a
person qualified to work with refrigerants must recover the refrigerant from within the sealed system. The
refrigerant must not be vented to atmosphere. Phone Rheem Service or their nearest Accredited Service
Agent to arrange for an inspection.

10
REGULAR CARE
MINOR SIX MONTH MAINTENANCE
It is recommended minor maintenance be performed every six months by the dwelling occupant.
The minor maintenance includes:
Operate the easing lever on the temperature pressure relief valve. It is very important you raise and
lower the lever gently. Refer to “Temperature Pressure Relief Valve” on page 11.
Warning: Exercise care to avoid any splashing of water, as water discharged from the drain line will
be hot. Stand clear of the drain line‟s point of discharge when operating the valve‟s lever.
Operate the easing lever on the expansion control valve (if fitted). It is very important you raise and
lower the lever gently. Refer to “Expansion Control Valve” on page 11.
Check the drain line from the safe tray (if one is installed) is not blocked.
MAJOR FIVE YEAR SERVICE
It is recommended a major five year service be conducted on the water heater.
Warning: Servicing of a water heater must only be carried out by a qualified person. Phone Rheem
Service or their nearest Accredited Service Agent.
Note: The five year service and routine replacement of any components, such as the anode and relief
valve(s), are not included in the Rheem warranty. A charge will be made for this work. Only genuine
replacement parts should be used on this water heater.
The major service includes:
Replace the temperature pressure relief 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 (refer to “Anode
Inspection and Replacement” on page 12).
Check the electric heating unit for excessive calcium build up or corrosion and replace if necessary.
Check and inspect the heat pump module for operation.
Visually check the unit for any potential problems.
Inspect all connections.
Check the condensate drain.
Check the drain line from the safe tray (if one is installed) is not blocked.
Note: The water heater may need to be drained during this service. After the completion of the service, the
water heater will take some time to reheat the water. Depending upon the power supply connection, hot
water may not be available until the next day.
HEAT PUMP SYSTEM
It is recommended the evaporator and refrigeration system is checked every five years. In particularly dusty
environments, it may be necessary to have the heat pump system checked and cleaned of dust and residue
on a more regular basis.

REGULAR CARE
11
TEMPERATURE PRESSURE RELIEF VALVE
This valve is near the top of the water heater and is essential for its
safe operation. It is possible for the valve to release a little water
through the drain line during each heating period. This occurs as the
water is heated and expands by approximately 1/50 of its volume.
Continuous leakage of water from the valve and its drain line may
indicate a problem with the water heater (refer to “Temperature
Pressure Relief Valve Running” on page 17).
Warning: Never block the outlet of this valve or its drain line for
any reason.
Operate the easing lever on the temperature pressure relief valve
once every six months. It is very important you raise and lower
the lever gently.
DANGER: Failure to do this may result in the water heater
cylinder failing, or under certain circumstances, exploding.
Warning: Exercise care to avoid any splashing of water, as
water discharged from the drain line will be hot. Stand clear of the
drain line‟s point of discharge when operating the valve‟s lever.
If water does not flow freely from the drain line when the lever is
lifted, then the water heater must be checked. Phone Rheem
Service or their nearest Accredited Service Agent to arrange for an
inspection.
The temperature pressure relief valve should be replaced at
intervals not exceeding 5 years, or more frequently in areas where
there is a high incidence of water deposits (refer to “Water Supplies”
on page 12).
EXPANSION CONTROL VALVE
In many areas, including Queensland, South Australia, Western Australia and scaling water areas, an
expansion control valve is fitted to the cold water line to the water heater. The expansion control valve may
discharge a small quantity of water from its drain line during the heating period instead of the temperature
pressure relief valve on the water heater.
Operate the easing lever on the expansion control valve once every six months. It is very important you
raise and lower the lever gently. The expansion control valve should be checked for performance or
replaced at intervals not exceeding 5 years, or more frequently in areas where there is a high incidence of
water deposits.
water
heater
drain
line
lift until water
flows from the
drain line –
lower gently

12
WATER SUPPLIES
This water heater must be installed in accordance with this advice to be covered by the Rheem
warranty.
This water heater is manufactured to suit the water conditions of most public reticulated water supplies.
However, there are some known water chemistries which can have detrimental effects on the water heater
and its operation and / or life expectancy. If you are unsure of your water chemistry, you may be able to
obtain information from your local water supply authority. This water heater should only be connected to a
water supply which complies with these guidelines for the Rheem warranty to apply.
CHANGE OF WATER SUPPLY
The changing or alternating from one water supply to another can have a detrimental effect on the operation
and / or life expectation of a number of components in this water heater.
Where there is a changeover from one water supply to another, e.g. a rainwater tank supply, bore water
supply, desalinated water supply, public reticulated water supply or water brought in from another supply,
then water chemistry information should be sought from the supplier or it should be tested to ensure the
water supply meets the requirements given in these guidelines for the Rheem warranty to apply.
ANODE
The vitreous enamel lined cylinder of the water heater is only covered by the Rheem warranty when the total
dissolved solids (TDS) content in the water is less than 2500 mg/L and when the correct colour coded anode
is used. If an incorrect colour coded anode is used in the water heater, any resultant faults will not be
covered by the Rheem warranty. In addition, the use of an incorrect colour coded anode may shorten the life
of the storage tank.
The correct colour coded anode is as shown in the following table:
Total Dissolved Solids
Anode colour code
0 –40 mg/L
Green
40 –150 mg/L
Green or Black
150 –400 mg/L
Black
400 –600 mg/L
Black or Blue
600 –2500 mg/L
Blue
2500 mg/L +
Blue (no cylinder warranty)
The changing of anodes must be carried out by a qualified person.
Note: Some water analysis reports may state the conductivity of the water rather than the level of total
dissolved solids. Conductivity, measured in microsiemens per centimetre (µS / cm), is directly proportional to
the TDS content of the water. TDS, in mg / L, is approximately 70% of the conductivity in µS / cm.
ANODE INSPECTION AND REPLACEMENT
The anode installed in your water heater will slowly dissipate whilst protecting the cylinder. The life of the
cylinder may be extended by replacing the anode.
If the anode is not replaced during a five year service (refer to “Major Five Year Service” on page 10) then
the maximum time after installation when the anode should be replaced for this water heater is 8 years.
For water supplies which are either softened, desalinated or where the water supply may alternate between
a water tank and a reticulated public supply or another supply, it is recommended the anode be replaced
within 5 years of installation.

WATER SUPPLIES
13
CAUTION
If the water supply has a TDS greater than 150 mg/L and a green anode has not been changed to a black
anode, or if the TDS is greater than 600 mg/L and the anode has not been changed to a blue anode, there is
the possibility the anode may become overactive and hydrogen gas could accumulate in the top of the water
heater during long periods of no use. In areas where this is likely to occur, the installer should instruct the
householder on how to dissipate the gas safely.
If, under these conditions, the water heater has not been used for two or more weeks the following procedure
should be carried out before using any electrical appliances (automatic washing machines and dishwashers)
which are connected to the hot water supply.
The hydrogen, which is highly flammable, should be vented safely by opening a hot tap and allowing the
water to flow. There should be no smoking or naked flame near the tap whilst it is turned on. Any hydrogen
gas will be dissipated. This is indicated by an unusual spurting of the water from the tap. Once the water runs
freely, any hydrogen in the system will have been released.
SATURATION INDEX
The saturation index (SI) is used as a measure of the water‟s corrosive or scaling properties.
Where the saturation index is less than –1.0, the water is very corrosive and the Rheem warranty does not
apply to the water heater. In a corrosive water supply, the water can attack copper parts and cause them to
fail.
Where the saturation index exceeds +0.40, the water is very scaling and the Rheem warranty does not apply
to the water heater.
Water which is scaling may be treated with a water softening device to reduce the saturation index of the
water.
CHLORIDE AND PH
Where the chloride level exceeds 250 mg/L the Rheem warranty does not apply to the water heater. In a
high chloride water supply, the water can corrode stainless steel parts and cause them to fail.
Where the pH is less than 6.0 the Rheem warranty does not apply to the water heater. pH is a measure of
whether the water is alkaline or acid. In an acidic water supply, the water can attack stainless steel parts and
cause them to fail.
Water with a pH less than 6.0 may be treated to raise the pH. The water supply from a rainwater tank in a
metropolitan area is likely to be corrosive due to the dissolution of atmospheric contaminants.
SUMMARY OF WATER CHEMISTRY ADVICE AFFECTING WARRANTY
The water heater is not suitable for certain water chemistries. Those chemistries are listed below. If the water
heater is connected at any time to a water supply with the following water chemistry, the Rheem warranty will
not cover any resultant faults:
Water Chemistry
Component
Total Dissolved Solids (TDS) > 2500 mg/L
water heater cylinder
Total Dissolved Solids (TDS) not suitable for anode type
water heater cylinder
Saturation Index (SI) < -1.0
water heater
Saturation Index (SI) > +0.4
water heater
Chloride > 250 mg/L
water heater
pH < 6.0
water heater

14
SAVE A SERVICE CALL
Check the items below before making a service call. You will be charged for attending to any condition or
fault that is not related to manufacture or failure of a part.
NOT ENOUGH HOT WATER (OR NO HOT WATER)
Is the electricity switched on?
Inspect the isolating switch marked “HOT WATER” or “WATER HEATER” at the switchboard and the
isolating switch at the water heater and ensure they are turned on.
Check the fuse marked “HOT WATER” or “WATER HEATER” at the switchboard.
Is a timer installed?
If a timer has been installed, ensure sufficient time has been allowed to reheat the storage tank.
Are you using more hot water than you think?
Is one outlet (especially the shower) using more hot water than you think?
Very often it is not realised the amount of hot water used, particularly when showering. Carefully review
the family‟s hot water usage. As you have installed an energy saving appliance, energy saving should
also be practised in the home.
Adjust your water usage pattern to take advantage of maximum
energy gains. Have your plumber install a flow control valve to
each shower outlet to reduce water usage.
Heat pump fault
Has the heat pump developed a fault and the red LED is flashing?
The heat pump will not operate and the water heater may switch
to backup heating mode using the booster heating unit.
Refer to “Heat Pump Is Not Operating” on page 15.
Temperature pressure relief valve running
Is the relief valve discharging too much water?
Refer to “Temperature Pressure Relief Valve Running” on page 17.
Water heater size
Do you have the correct size water heater for your requirements?
The sizing guide in the sales literature and on the Rheem website (www.rheem.com.au) suggests
average sizes that may be needed.
WATER NOT HOT ENOUGH
You may find that due to heavy hot water usage the water temperature may be lower than normally
expected, due to insufficient heating time being allowed. You will need to carefully plan your use of the hot
water on such occasions.
WATER TOO HOT
The water heater during heat pump operation will heat the water to a temperature of 60°C. In booster heating
mode or back up heating mode the water will be heated to 70°C. The heat pump will operate when the
ambient air temperature is between a minimum of 3°C to 5°C and maximum of 45°C to 55°C. The booster
heating unit will operate in booster heating mode when the ambient air temperature is outside of this
temperature range, if heating is required. This is normal operation.
If a heat pump component has developed a fault condition, the heat pump will not operate and the water
heater will switch to backup heating mode to ensure a supply of hot water. In backup heating mode, the
booster heating unit will operate if heating of the water is required, regardless of the ambient air temperature.
The red LED will flash to indicate the fault mode that has occurred. Refer to “Heat Pump Is Not Operating” on
page 15.

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15
HEAT PUMP IS NOT OPERATING
There must be power available at the water heater and to the heat pump for the heat pump to operate and
for the LEDs to glow or flash.
Time controlled power supply –no power at the water heater (green and red LEDs are off)
If the water heater is connected to a time controlled power supply, then during periods of no power
supply at the water heater the LEDs will be off.
This is not a fault condition, but a result of no power being available to energise the LEDs.
Check the hours of supply from the electricity retailer or the timer settings if one is installed.
The green LED will recommence glowing or flashing when power is available again at the water heater.
Heat pump operating range
The heat pump‟s operating range is between an ambient air temperature of a minimum of 3°C to 5°C
and a maximum of 45°C to 55°C. The heat pump will not operate when the ambient air temperature is
outside the heat pump‟s operating range.
If heating is required, the water heater will commence heating with the booster heating unit in booster
heating mode (long green flash) instead. The water will be heated to 70°C during these periods.
At the completion of this heating cycle by the booster heating unit (long green flash), the thermostat
controlling the booster heating unit opens circuit cutting power to the heat pump causing the green LED
to go out.
This is not a fault condition, but a result of the power being cut to the heat pump by the thermostat.
The green LED will remain off for an extended period of time until the water temperature in the top of the
water heater drops to below 62°C and the thermostat closes circuit reinstating power to the heat pump.
The green LED will then flash rapidly for three (3) seconds before recommencing to glow or emit a
series of single flashes.
The green LED will glow (standby mode –water is hot) if the water temperature in the lower part of the
water heater is 50°C or more.
The green LED will flash if the water temperature in the lower part of the water heater is less than 50°C.
If the ambient air temperature has moved back to within the heat pump‟s operating range, heating of the
water by the heat pump will recommence (3 x green flashes). It may take up to 45 minutes for the heat
pump to start up depending upon when it last operated. If the ambient air temperature is outside of the
heat pump‟s operating range, the water heater will switch to the booster heating unit (long green flash).
Green LED is off
There may be a fault condition with the heat pump if:
there is power available at the water heater and the green LED is off, and
the water heater has not operated outside of the heat pump‟s operating range – refer to “Heat
pump operating range” on page 15.
Before phoning to arrange a service inspection:
inspect the isolating switch marked “HOT WATER” or “WATER HEATER” at the switchboard and
the isolating switch (if one is installed) at the water heater and ensure they are turned on
check the fuse marked “HOT WATER” or “WATER HEATER” at the switchboard
if a timer has been installed, check the time settings
check the power supply tariff the water heater is connected to and confirm whether power should be
available to the water heater.
If the green LED is off and one of these conditions is not the cause, refer also to “Possible fault
condition”on page 16.

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16
Possible fault condition (1 or 3 to 9 x red flashes)
If the heat pump has developed a fault, the heat pump will not operate, the red LED will flash a fault
mode of a series of either one (1) or three (3) to nine (9) flashes.
If a single flash or a series of three (3) to eight (8) red flashes occurs, the water heater will switch to
backup heating mode to ensure a supply of hot water.
Refer to “Backup heating mode and series of red flashes” on page 16.
If a series of nine (9) red flashes occurs, the heat pump will not switch to backup heating mode. Phone
Rheem Service or their nearest Accredited Service Agent to arrange for an inspection.
Backup heating mode and series of red flashes (1 or 3 to 8 x red flashes)
During the backup heating mode by the booster heating unit, caused by a possible heat pump fault
condition, the red LED will emit a series of flashes. Count the number of flashes.
At the completion of a heating cycle by the booster heating unit in the backup heating mode and the
water temperature reaches 70°C, the thermostat controlling the booster heating unit opens circuit cutting
power to the heat pump causing the red LED to go out. The fault mode is recorded to the heat pump
controller‟s memory. The fault condition which led to the red LED flashing may be cleared when the
backup heating cycle is completed.
Both LEDs will remain off for an extended period of time until the water temperature in the top of the
water heater drops to below 62°C and the thermostat closes circuit reinstating power to the heat pump.
The green LED will flash rapidly for three (3) seconds and then extinguish. The red LED will then
recommence to flash the fault mode for 27 seconds and then extinguish.
If the red LED then recommences to flash after the 27 second period, the fault condition which led to the
red LED flashing may not have cleared and there may be a problem with the heat pump. Count the
number of red flashes and phone Rheem Service or their nearest Accredited Service Agent to arrange
for an inspection.
If the green LED recommences to glow or flash after the 27 second period, the fault condition may have
cleared.
The green LED will glow (standby mode –water is hot) if the water temperature in the lower part of the
water heater is 50°C or more.
The green LED will flash if the water temperature in the lower part of the water heater is less than 50°C.
Note: If the green LED is glowing, then to check whether there may be a problem with the heat pump,
open a hot tap and allow to run for ten to fifteen minutes. This will draw cold water into the lower part of
the water heater and the green LED will commence to flash. Close the hot tap when the green LED
commences to flash.
The heat pump will commence to operate after the green LED starts flashing. It may take up to
45 minutes for the heat pump to start up depending upon when it last operated.
If the heat pump stops operating and the red LED recommences to flash, the fault condition which led to
the red LED flashing may not have cleared and there may be a problem with the heat pump. Count the
number of red flashes and phone Rheem Service or their nearest Accredited Service Agent to arrange
for an inspection.
Note: If the ambient air temperature is outside of the heat pump‟s operating range, the water heater may
switch to the booster heating unit (long green flash) to heat the water in booster heating mode.
The fault mode is cleared from the heat pump controller‟s memory after the water heater successfully
completes a full heat up cycle using the heat pump.

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TEMPERATURE PRESSURE RELIEF VALVE RUNNING
Normal Operation
It is normal and desirable this valve allows a small quantity of
water to escape during the heating cycle. However, if it discharges
more than a bucket full of water in 24 hours, there may be another
problem.
Continuous dribble
Try gently raising the easing lever on the relief valve for a few
seconds (refer to “Temperature Pressure Relief Valve” on
page 11). This may dislodge a small particle of foreign matter and
clear the fault. Release the lever gently.
Steady flows for long periods (often at night)
This may indicate the mains water pressure sometimes rises
above the designed pressure of the water heater. Ask your
installing plumber to fit a pressure limiting valve.
Warning: Never replace the relief valve with one of a higher
pressure rating.
Heavy flows of hot water until the water heater is cold - then stops until water reheats
The water heater must be switched off at the isolating switch or switchboard. Phone Rheem Service or
their nearest Accredited Service Agent to arrange for an inspection.
EXPANSION CONTROL VALVE RUNNING
If an expansion control valve is fitted in the cold water line to the water heater (refer to page 37)it may
discharge a small quantity of water instead of the temperature pressure relief valve on the water heater. The
benefit is that energy is conserved as the discharged water is cooler.

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HIGHER THAN EXPECTED ELECTRICITY BILLS
With the installation of your new air sourced heat pump water heater, maximum electrical energy savings can
be achieved. Should you at any time, feel your electricity bill is higher than expected, we suggest you check
the following points:
Is the water heater operating in backup heating mode with the red LED flashing?
If there is a fault condition with the heat pump system, the water heater will default to backup heating
mode to ensure a supply of hot water. Check to see if the red LED is flashing as this will indicate there
may be a fault with the system.
Refer to “Heat Pump Is Not Operating” on page 15.
Is the relief valve running excessively?
Refer to “Temperature Pressure Relief Valve Running” on
page 17.
Is one outlet (especially the shower) using more hot water than
you think?
Refer to “Not Enough Hot Water” on page 14.
Is there a leaking hot water pipe, dripping hot water tap, etc?
Even a small leak will waste a surprising quantity of hot water and energy. Replace faulty tap washers,
and have your plumber rectify any leaking pipe work.
Has there been an increase in hot water usage?
An increase in hot water usage will result in an increase in heat pump operation.
Has your water heating tariff rate been increased by your electricity retailer since your previous bill?
Is the heat pump water heater on the same tariff as the water heater replaced?
The impact on an electricity bill will depend upon the tariff arrangement of the water heater replaced and
where you live. Contact your energy provider for more information on tariff arrangements and cost
comparisons.
Prolonged periods of use when the ambient air temperature is outside of the heat pumps operating
range will increase the amount of boosting and increase running costs.
IF YOU HAVE CHECKED ALL THE FOREGOING AND STILL BELIEVE YOU NEED ASSISTANCE,
PHONE RHEEM SERVICE OR THEIR NEAREST ACCREDITED SERVICE AGENT.

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INSTALLATION
THIS WATER HEATER IS FOR OUTDOOR INSTALLATION ONLY.
THIS WATER HEATER IS NOT SUITABLE FOR POOL HEATING.
INSTALLATION STANDARDS
The water heater must be installed:
by a qualified person, and
in accordance with the installation instructions, and
in compliance with Standards AS/NZS 3500.4, AS/NZS 3000 and all local codes and regulatory authority
requirements.
In New Zealand, the installation must also conform with Clause G12 of the New Zealand Building Code.
Victorian Installers
Notice to Victorian Installers from the Victorian Plumbing Industry Commission if this solar water heater is
installed in a new Class 1 dwelling in the State of Victoria. The system model number is to be recorded on
the Certificate of Compliance. It is also a requirement to provide the householder with permanent
documentation recording the system model number exactly as it is shown in the „List of systems capable of
complying with the regulations‟ published by Sustainability Victoria (see www.sustainability.vic.gov.au). This
documentation may be in the form of an indelible label adhered to the solar storage tank, or other suitable
form placed in an accessible location, such as the meter box, for later inspection.
WATER HEATER APPLICATION
This water heater is designed for use in a single family domestic dwelling for the purpose of heating potable
water. Its use in an application other than this may shorten its life.
If this water heater is to be used where an uninterrupted hot water supply is necessary for the application or
business, then there should be redundancy within the hot water system design. This should ensure the
continuity of hot water supply in the event that this water heater was to become inoperable for any reason.
We recommend you provide advice to the system owner about their needs and building backup redundancy
into the hot water supply system.
The 551 325 model water heater is recommended for connection to a minimum 16 hour per day power
supply. The 551 410 model water heater is recommended for connection to a 24 hour per day power supply.
A Rheem heat pump water heater consumes less energy than an electric water heater. The impact on an
electricity bill will depend on the tariff arrangement of the water heater replaced and the installation location.
Contact the energy provider for more information on tariff arrangements and cost comparisons.
STORAGE TANK AND HEAT PUMP MODULE
The heat pump water heater is made of two main components, the storage tank and the heat pump module.
For transport and handling (weight) purposes both items are shipped separately and designed to be
assembled at the installation site. The water heater must not be operated until both components are
assembled. Refer to “Heat Pump and Tank Assembly” on page 25.
Take care when handling the heat pump module. The jacket of the heat pump module needs to be handled
gently so as not to cause damage.
Care must be taken during transportation and handling. Do not lay the heat pump module down and
do not tilt the heat pump module or the heat pump and storage tank assembly more than 30° from the
vertical. This will displace the compressor lubricating oil. If the heat pump module or heat pump and storage
tank assembly has been tilted more than 30° from the vertical during handling, it will need one hour to drain
back before the power to the water heater can be switched on, otherwise damage to the compressor may
result.
All packaging materials must be removed from the water heater prior to its installation. This includes the
removal of the cardboard base of the carton from the underside of the water heater.

INSTALLATION
20
WATER HEATER LOCATION
The water heater is suitable for outdoor installation only. The water heater should be installed close to the
most frequently used outlet and its position chosen with noise, safety and service in mind. Make sure people
(particularly children) will not accidentally touch the air inlet louvres and outlet grille and that they are clear of
obstructions and shrubbery.
It is advisable to install the water heater away from bedroom
or living room windows as the system controls can generate a
level of noise whilst they are operating. Consider the location
in relation to neighbours‟bedrooms and living room windows.
Clearance must be allowed for servicing of the water heater.
The water heater must be accessible without the use of a
ladder or scaffold. Make sure the temperature pressure relief
valve lever is accessible and the top and front covers, system
controls and thermostat can be removed for service.
You must be able to read the information on the rating plate.
If possible leave headroom of one water heater height so the
anodes can be inspected or replaced. Remember you may
have to remove the entire water heater later for servicing.
The water heater is to be installed at ground or floor level and must stand vertically upright on a stable base,
as acceptable to local authorities, of a minimum size 900 mm wide x 650 mm deep. The heat pump module
must be fully supported by the stable base.
The base of the water heater is made of corrosion resistant material, and it may be placed directly in contact
with the supporting surface. It is not necessary to allow for free air circulation under the base of the water
heater.
Note: The water heater should not be placed in direct contact with a concrete surface that is less than two
months old and not fully cured as this may attack the metal coating of the water heater base. A moisture
barrier should be used between the two surfaces in this instance.
The water heater must be installed with a clearance of at least 100 mm from a wall. A clearance of at least
300 mm is required perpendicular from both the front air inlet louvres and the outlet grille to any wall or
obstruction. Refer to the dimensions diagram on page 24.
The water heater must not be installed in an area with a corrosive atmosphere where chemicals are stored or
where aerosol propellants are released. Remember the air may be safe to breathe, but the chemicals may
attack the materials used in the heat pump system.
SAFE TRAY
Where damage to property can occur in the event of the water heater leaking, the water heater must be
installed in a safe tray. Construction, installation and draining of a safe tray must comply with AS/NZS 3500.4
and all local codes and regulatory authority requirements.
FREEZE PROTECTION
The water heater has a freeze protection system. The freeze protection system will protect the water heater
from damage, by preventing ice forming in the waterways of the water heater, in the event of freezing
conditions occurring.
If the ambient air temperature falls below 1°C and the heat pump is not operating, the system will operate the
circulator periodically. During this freeze protection cycle, the circulator will operate for thirty (30) seconds
and then rest for fifteen (15) minutes, before the cycle is recommenced. Water is circulated from the storage
tank through the heat pump circuit, to prevent freezing in the connecting pipe work and heat pump module.
The green LED will flash a series of four (4) flashes whilst the circulator is operating.
The water heater has NO WARRANTY for freeze damage if power is unavailable at the water heater.
Warning: In areas where the ambient air temperature may fall below 1°C, power must be available to the
water heater at all times to prevent freezing in the heat pump circuit.