Rheem Air Sourced 310 Heat Pump Water Heater

About Your Water Heater

Model Type

The Rheem air sourced heat pump water heater (model 551 310) is designed for outdoor installation only and is recommended for connection to a minimum 16-hour per day power supply. It consumes less energy than an electric water heater.

The unit features a Rheemglas vitreous enamel lined steel cylinder. The evaporator absorbs heat from the surrounding air and transfers it to the water. When hot water is drawn, the thermostat activates a fan, compressor, and circulator. Air is drawn in, heat is absorbed, and warm, moist air is discharged. This process continues until water reaches 60°C.

The heat pump operates when ambient air temperature is 5°C or higher. A booster heating unit operates below 5°C if heating is required. Efficiency increases with ambient air temperature.

Electric Boosting

When ambient air temperature drops below 7°C, ice may form on the evaporator, reducing efficiency. Below 5°C, the heat pump deactivates, and the booster heating unit takes over. The evaporator may defrost during this period. The boost capacity is 220 litres, heating water to 60°C. The booster thermostat is not adjustable.

Mains Pressure

The water heater connects directly to the mains water supply. A pressure limiting valve is required if supply pressure exceeds specified limits. A minimum water supply pressure of 200 kPa is needed for effective heat pump operation.

How Hot Should the Water Be?

The system heats water to approximately 60°C. If the ambient temperature is outside the heat pump's range, the booster unit automatically heats water to 60°C. Stored water temperature must not be below 60°C per National Plumbing Standard.

Hotter Water Increases the Risk of Scald Injury

This water heater can deliver scalding temperatures. Always check water temperature before use. A temperature limiting device is recommended for bathrooms and ensuites to keep water below 50°C, reducing scald risk while allowing hotter water to kitchens and laundries.

Temperature Adjustment

Thermostats for the heat pump and booster unit are factory set and not adjustable.

Warning

This water heater is intended for use by persons with experience and knowledge. It is not for use by persons with reduced physical, sensory, or mental capabilities, or by children. Supervise children to prevent interference.

The unit uses 240V AC electrical power. Access covers expose 240V wiring and must only be removed by authorized personnel.

Safety Precautions:

• Do not use aerosols, stain removers, or household chemicals near the unit, as their gases can be corrosive.
• Do not store swimming pool chemicals or household cleaners near the unit.
• Ensure air inlet and outlet louvres are not obstructed.

The water heater is equipped with a thermostat, two over-temperature energy cut-outs, and a temperature pressure relief valve. These must not be tampered with or removed. Operation of the over-temperature cut-out indicates a dangerous situation and requires service by an authorized person. Damaged electrical supply conduit must be replaced by an authorized person. Tampering with safety devices or improper installation voids the warranty.

Operation

To Turn Off: Switch off the electrical supply at the isolating switch and close the cold water isolation valve.

To Turn On: Open the cold water isolation valve fully and switch on the electrical supply. The heat pump may take up to 30 seconds to start. It operates when heating is required, the compressor is cool, and power is available. Below 5°C, the booster unit operates.

Timer Control: A weatherproof timer can be installed to manage operating times.

Going on Holidays: Leave switched on for short periods; switch off for longer periods.

Installation Correctness: Must comply with AS/NZS 3500.4, AS/NZS 3000, and local codes. In New Zealand, conform to Clause G12 of the Building Code.

Water Chemistry: Some chemistries can be detrimental. Refer to "Water Supplies" on page 9.

Environment

At the end of its service life, a qualified person must recover the refrigerant before disposal. Do not vent refrigerant to atmosphere.

Regular Care

Temperature Pressure Relief Valve

This valve is essential for safe operation. It may release a small amount of water during heating cycles. Continuous leakage indicates a problem. Never block the outlet or drain line. Gently operate the easing lever every six months to prevent seizing. Failure to do so can cause cylinder failure or explosion. If water does not flow freely when the lever is lifted, have the unit checked. The valve should be checked or replaced every 5 years, or more frequently in areas with water deposits.

Expansion Control Valve

Fitted in some areas, this valve may discharge water instead of the TPR valve. Gently operate its easing lever every six months. Check or replace every 5 years, or more frequently in areas with water deposits.

Heat Pump System

The evaporator and refrigeration system should be checked every five years. In dusty environments, more frequent cleaning of dust and residue may be necessary.

Water Supplies

This water heater is designed for most public water supplies, but certain water chemistries can be detrimental. Consult your local water supply authority if unsure. Warranty applies only if water supply complies with guidelines.

Change of Water Supply

Alternating water supplies (e.g., rainwater, bore water) can affect operation and lifespan. Obtain water chemistry information before changing supplies.

Anode

The vitreous enamel cylinder is covered by warranty if Total Dissolved Solids (TDS) are less than 2500 mg/L and the correct colour-coded anode is installed. An incorrect anode voids the warranty.

Anode Colour Code vs. TDS:

• 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)

Anodes must be changed by a plumber or authorized service person. Note: Conductivity (µS/cm) is proportional to TDS (mg/L).

Anode Inspection

Inspect the anode every 8 years (or every 5 years for softened/desalinated/alternating supplies) to extend cylinder life.

Caution

If TDS is high (>150 mg/L with green anode, or >600 mg/L with blue anode), the anode may become overactive, potentially accumulating hydrogen gas. If the unit has been unused for two weeks, vent any accumulated gas by opening a hot tap (no smoking or naked flame nearby).

Saturation Index (SI)

SI measures water corrosiveness or scaling. SI less than -1.0 (corrosive) or greater than +0.40 (scaling) voids warranty. Scaling water may be treated with a water softener.

Chloride and pH

Chloride levels exceeding 250 mg/L or pH less than 6.0 (acidic) void warranty. Acidic water can corrode stainless steel parts.

Summary of Water Chemistry Advice Affecting Warranty

Warranty exclusions apply for TDS > 2500 mg/L, unsuitable TDS for anode type, SI < -1.0, SI > +0.4, Chloride > 250 mg/L, and pH < 6.0.

Save a Service Call

Not Enough Hot Water (Or No Hot Water)

• Check electricity supply and isolating switches.
• Check timer settings.
• Review hot water usage patterns. Consider a flow control valve for showers.
• Heat Pump Fault: Unit may switch to backup heating (110L boost). Refer to "Heat Pump Is Not Operating".
• TPR Valve Running: May indicate a problem. Refer to "Temperature Pressure Relief Valve Running".
• Water Heater Size: Ensure the unit is correctly sized for your needs.

Water Not Hot Enough

This can occur due to heavy usage or insufficient heating time. Plan usage accordingly.

Water Too Hot

If a heat pump component fails, the unit may switch to backup heating mode, potentially reaching 70°C (110L boost). Contact Rheem Service.

Heat Pump is Not Operating

• Time Controlled Power Supply: Ensure power is available.
• Heat Pump Operating Range: Operates at 5°C ambient or higher. Booster operates below 5°C (220L boost to 60°C).
• Thermal Cut Out Activated: Unit switches to booster heating mode (220L boost to 60°C). It resets automatically when the compressor cools. If it deactivates within 5 minutes after running a hot tap, contact Rheem Service.
• Heat Pump Fault: Unit switches to backup heating mode (110L boost to 70°C). Contact Rheem Service.

Expansion Control Valve Running

May discharge a small quantity of water.

Temperature Pressure Relief Valve Running

• Normal Operation: Small water escape during heating is normal. More than a bucket in 24 hours may indicate a problem.
• Continuous Dribble: Gently raise the easing lever to clear potential debris.
• Steady Flows: May indicate high mains pressure; consider a pressure limiting valve.
• Heavy Flows: Switch off the unit and contact Rheem Service.

Higher Than Expected Electricity Bills

Check if the unit is in backup heating mode, if the relief valve is running excessively, if hot water usage has increased, if there are leaks, if your electricity tariff has changed, or if operating outside the heat pump's ambient temperature range.

If issues persist after checking these points, contact Rheem Service.

Installation

Important: For outdoor installation only. Not suitable for pool heating. Comply with AS/NZS 3500.4, AS/NZS 3000, and local authority requirements. In New Zealand, conform to Clause G12 of the Building Code.

The 551 310 model is recommended for a minimum 16-hour per day power supply.

Storage Tank and Heat Pump Module

The unit comprises two main components: the storage tank and the heat pump module, shipped separately for assembly on site. Do not operate until assembled. Handle the heat pump module gently. Do not tilt it more than 45° from vertical; allow 1 hour to settle if tilted.

Water Heater Location

Install outdoors, close to the most frequently used outlet. Position for noise, safety, and service access. Ensure clear access to air inlet/outlet louvres. Avoid proximity to bedroom/living room windows due to potential operating noise. Allow clearance for servicing (accessible without ladder/scaffold). Ensure rating plate is readable. Leave headroom for anode inspection/replacement.

Installation Site

Install on a level slab or solid base, standing vertically. Avoid direct contact with new concrete; use a moisture barrier. Maintain at least 100 mm clearance from walls and 300 mm perpendicular clearance from air inlet/outlet louvres. Avoid corrosive atmospheres.

Mains Water Supply

If mains pressure exceeds specified limits, fit a pressure limiting valve. A minimum supply pressure of 200 kPa is required.

Tank Water Supply

If using a tank supply with pressure below 200 kPa, install a pressure pump system. Ensure adequate pipe sizing and a full flow valve.

Purging Air

Purge air from the system using the air bleed valve before operation to prevent non-operation or overheating.

Hot Water Delivery

The unit can deliver scalding temperatures. A temperature limiting device is recommended for bathrooms/ensuites to keep water below 50°C. Ensure compliance with AS/NZS 3500.4 for safe delivery temperatures.

Circulated Hot Water Flow and Return System

This unit is not designed for circulated hot water systems. If required, bypass the unit and use a secondary water heater. Temperature limiting devices cannot be circulated.

Reducing Heat Losses

Insulate cold and hot water lines according to AS/NZS 3500.4. Insulation must be weatherproof and UV resistant if exposed.

Anode Types

Warranty coverage depends on TDS levels and correct anode type. Incorrect anodes can lead to hydrogen gas accumulation. Consult page 10 for safe gas dissipation instructions.

Saddling - Pipe Work

Use self-drilling screws (max 13mm) for pipe clips to prevent cylinder damage. Damage to the cylinder voids the warranty.

Heat Pump and Tank Assembly

The unit consists of a storage tank and a heat pump module, assembled on site. Warning: Assemble, plumb, and fill with water before connecting power.

Step 1: Storage Tank Positioning

Remove all packaging. Position the storage tank on a level slab, at least 100 mm from the wall, with 300 mm clearance for air louvres. Ensure power and sensor cables hang clear.

Step 2: Heat Pump Module Preparation

Place the heat pump module in front of the tank. Open the carton, remove lifting bars, and then remove the carton from the module.

Step 3: Air Louvre Removal

Using a Phillips head screwdriver, remove the six screws from each of the two air louvres (12 screws total).

Step 4: Electrical Cover Removal

Remove the mounting screw from the side of the electrical cover and gently remove it. Handle the cover carefully to avoid damaging electronic controls.

Step 5: Lifting Bars

Insert the two lifting bars into the slots at the front of the heat pump module chassis and push them through to engage the slots at the rear. Ensure they provide a firm grip for lifting.

Step 6: Heat Pump Module Placement

With two people, lift the heat pump module onto the storage tank. Ensure water fittings align with the tank's inlet/outlet openings and screw holes align with nutserts. Avoid resting the module on cables. The module weighs approximately 48 kg.

Step 7: Heat Pump Module Attachment

Remove the lifting bars and secure the heat pump module to the storage tank using the three provided M6 screws.

Step 8: Water Fitting Caps

Remove the caps from the inlet and outlet water fittings on the storage tank.

Step 9: Inlet Flexible Braided Hose

Attach the flexible braided hose marked "INLET" to the inlet water fitting. Tighten the swivel nut with a 24 mm spanner and seat the pipe seal ring.

Step 10: Outlet Flexible Braided Hose

Attach the flexible braided hose marked "OUTLET" to the outlet water fitting. Tighten the swivel nut with a 24 mm spanner and seat the pipe seal ring.

Step 11: Air Bleed Valve

Open the air bleed valve screw one turn anticlockwise to allow air to escape during filling. Leave the screw in this position.

Step 12 & 13: Cable Connections

Connect ONE tank sensor cable plug firmly into the "TANK SENSOR" connector on the control board. The second plug is a backup. Coil excess cable and stow it. Connect the 4-pin power cable plug to its connector on the control board.

Step 14: Electrical Cover Replacement

Replace the electrical cover and secure it with the mounting screw.

Step 15: Water Connections

Connect the cold water supply, hot water pipe work, and the temperature pressure relief valve with its drain line. Refer to "Connections – Plumbing" on page 28.

Step 16: Water Supply

Turn on the cold water supply and fill the water heater. Check for leaks at pipe work and hose connections. Do not switch on electrical supply yet. Refer to "To Fill And Turn On The Water Heater" on page 35.

Step 17: Air Louvre Attachment

Replace the two air louvres, ensuring the longer skirt is at the bottom, and refit the twelve attachment screws.

Step 18: Electrical Connection

Refer to "Connections – Electrical" on page 30.

Step 19: Commissioning

Refer to "Commissioning" on page 35.

Connections

Plumbing

Connection Sizes: Hot water: RP³/20; Cold water: RP³/20; Relief valve: RP¹²/15. All plumbing must comply with AS/NZS 3500.4 and local authority requirements.

Water Inlet and Outlet: Clear and purge pipework before connection. Use brass or copper olives and thread sealant. Install an isolation valve and non-return valve on the cold water line. A disconnection union is required at the inlet and outlet. Ensure plastic dip tube/liner in fittings remains in place.

Pipe Sizes: For mains pressure, the cold water line should be the same size or larger than the hot water line.

Temperature Pressure Relief Valve: Fit before operation. Seal thread with Teflon tape. Install with drain pointing downwards. Insulate the valve and pipework.

Electrical

Power Supply: Connect to a 240V AC 50Hz mains supply via its own circuit with an isolating switch. The unit operates on a sine wave at 50 Hz.

Megger Reading: Perform insulation tests between active-earth and neutral-earth only. Active-neutral tests will damage electronics. A normal insulation test result is between 100 kΩ and 660 kΩ.

Booster Heating Unit and Thermostat: Booster activates below 5°C. Thermostat is not adjustable.

Timer: A weatherproof timer can be installed to control operating times.

Recommendation: Minimum 16-hour per day power supply for the 551 310 model.

Multiple Installations

Units can be installed in banks using the Equa-Flow manifold system for high hot water demand. Ensure manifolds balance flow. Maximum 8 heaters per bank. Heaters must be the same model. Comply with AS/NZS 3500.4 for pipe sizing. Install isolation valves, non-return valves, and potentially pressure limiting/expansion control valves. Use full flow gate/ball valves on each heater's branches. Allow 900 mm clearance for access and servicing. TPR valve drain lines can connect to a common tundish.

Installation Requirements: Turn units 90° so front covers face adjacent heaters. If next to a wall, intake towards the wall, discharge away. Maintain 900 mm clearance between units and walls.

Commissioning

To Fill and Turn On the Water Heater

Ensure the unit is filled with water and a satisfactory megger reading is obtained before switching on power.

1. Open all hot water taps.
2. Open the cold water isolation valve fully. Air will be expelled from the taps.
3. Close taps as water flows freely.
4. Check pipework for leaks.
5. Switch on the electrical supply at the isolating switch.
6. Set the timer if installed.

Allow up to 30 seconds for the heat pump to start. It operates when heating is required, the compressor is cool, and power is available. Below 5°C, the booster unit operates. Wait five minutes after activation to ensure correct operation. Explain the system's functions to the householder.

To Turn Off the Water Heater

Switch off the electrical supply at the isolating switch and close the cold water isolation valve.

Draining the Water Heater

1. Turn off the water heater and close all hot water taps.
2. Gently operate the relief valve release lever to release pressure.
3. Undo the union at the cold water inlet, attach a hose to a drain.
4. Operate the relief valve again to allow air in and drain the water.

Warranty

Warranty Conditions

Applicable to water heaters manufactured from August 2010. Must be installed per instructions and local requirements. Replaced components retain the balance of the original warranty. Owner responsible for transport costs if outside metropolitan areas or more than 25 km from a Rheem branch/agent. Owner responsible for costs related to unsafe access. Warranty covers Rheem parts only, not installer-supplied components (e.g., pressure limiting valves).

Warranty Exclusions

Exclusions include accidental damage, misuse, incorrect installation, unauthorized repairs, issues due to plumbing, leaks not related to the unit, power/water supply failures, excessive water pressure/temperature, corrosive atmosphere, ice formation, improper location, or water supply not meeting guidelines. Consequential losses (e.g., damage to property) due to leaks are excluded.

Warranty Details

Rheem will repair or replace components failing within the warranty period. Specific warranty periods apply to components, sealed systems, and cylinders, varying by installation type (single-family dwelling vs. other). Refer to the document for specific year-by-year coverage.

Contact Rheem Australia Pty Ltd for service: 131 031 (Australia) or 0800 657 335 (New Zealand).