181L Roof Top Solar: Key Attributes

The Solahart L Series is a roof mounted, open circuit solar water heater specifically designed to provide economical service in medium to high solar gain areas. It is not recommended for use in frost or poor water chemistry areas.

The L Series is ingenious in its simplicity. The black polyester powder coated aluminium absorber collects the sun's heat and transfers it to the water in the 7 risers. Copper is used for the risers for its high thermal conductivity ensuring the maximum amount of heat energy is passed to the water. As the water in the risers is heated, it rises into the tank to be replaced by cooler water from the tank. The solar heated water is then stored ready for use - hot water free from the sun.

  •  Stylish slimline roof mount design
  •  Can cut water heating energy use by up to 60%^
  •  Reliable, low maintenance operation
  •  Eligible for Government rebates and incentives

 * The suggested price is comprised of RRP less the applicable solar incentive and excluding installation. Solar incentive value applies to 181L system in Zone 3.

^ Energy savings of up to 60% shown is based on Australian Government approved TRNSYS simulation modelling of a Solahart 181L and using a small load in Zone 3 and apply when replacing an electric water heater. Any savings will vary depending upon your location, type of Solahart system installed, orientation and inclination of the solar collectors, type of water heater being replaced, hot water consumption and fuel tariff. Maximum financial savings off your hot water bill are achievable when replacing an electric water heater on continuous tariff.

† Solahart Warranty Details: 5/5/5 warranty; 5 year cylinder and collectors supply, 5 year parts, 5 year labour.

181L Solar Specifications

Tank Model 180L Tank   181L System
Storage Capacity 180 litres 180 litres
Boost Capacity (Electric) 90 litres 90 litres
Weight Empty 62 kg 97 kg
Weight Full 242 kg 297 kg
A-Width* 1.62 m 1.67 m
B-Length* 0.51 m 2.53 m

 * For servicing and safe access, a space equal to the tank length should be left on the water connection end of the system and 1m (40in) should be left on the three other sides of the installation. The L system (if installed with a TRV system) can be installed as a solar preheater with a Solahart inline gas booster water heater. Refer to the Solahart gas booster specification sheet for further details on the gas booster.

L Collectors
Aperture (heating) Area 1.87 m2
Length 1943 mm
Width 1027 mm
Height 83 mm
Capacity 1.2 litres
Empty 29 kg
Full 32 kg
Working Pressure 1000 kPa 
145 psi
Absorber Surface Black polyester powder coat
Absorber Material aluminium
Riser Material copper tube
Tray Material 0.7 mm aluminium
Insulation Material - Base 38 mm polyester blanket
Glass 3.2 mm tempered low iron glass

 *Weight includes fittings

Electric Boost Specifications
Heating Unit Type Cooper sheath immersion element
Supply Voltage 240 V -250 V
Recovery Rate (litres/hour) @ 240V and Temperature Rise of:
1.8 8 51 39 31
2.4 10 68 52 41
3.6 15 103 77 62
4.8 20 137 103 83


Water Supply
TPR Valve Setting 1000 kPa 
145 psi
ECV* Setting 850 kPa 
125 psi
Max. Supply Pressure
With ECV 680 kPa
Without ECV 800 kPa
Water Connections
Cold DN15 compression nut fitting (RP 3/4 tank fitting)
Hot R 1/2

 *Expansion Control Valve.


How Roof Top Solar Systems Work

Solar Operation

The 181L solar system has its vitreous enamel lined solar storage tank installed on the roof directly coupled to the solar collectors. It works on the simple scientific fact that hot water rises. As the sun heats the water in the solar collectors, the increase in temperature causes the water to rise through an insulated copper pipe into the storage tank. This allows cooler water from the solar storage tank to flow into the solar collectors to be heated by the sun‟s energy. This process continues while solar energy is available.

Orientation of Solar Collectors

To help maximise system performance, solar collectors should be installed with an optimum orientation facing true north (in the southern hemisphere) or true south (in the northern hemisphere). Always check for true north or true south using a compass or other suitable device.

To help maximise system performance, solar collectors should be installed with an optimum inclination. This is equal to 90% to 100% of the local latitude angle when collectors are oriented within 60° of true north or true south, and between 10° and 20° if the collectors are oriented between 60° and 90° from the optimum orientation. Generally, improved summer performance is obtained from an angle of inclination less than the optimum angle and improved winter performance is obtained by an angle of inclination greater than the optimum angle. If the angle of inclination varies by 20° from the optimum angle, the solar collectors will receive about 10% less total annual solar radiation.

Frost/Freeze Protection

An Open Circuit system does not have freeze protection and is not suitable for installation in areas prone to freeze conditions. Freeze conditions occur below 5°C (41°F). This system has NO WARRANTY for freeze damage. In areas that are prone to frost / freezing, a Closed Circuit system should be used.


Solar Boosting

In-Tank Boosting

An isolating switch is installed in the electrical meter box for an electrically in-tank boosted model. This should be left switched on to allow the booster heating unit to operate if required. The booster heating unit is for heating the water at times of low solar energy gain, such as during very cloudy or rainy weather, or during the colder months. The booster heating unit will only activate if heating is required and power is available from the switchboard. When the water is below the thermostat setting, the booster heating unit will turn on and heat the water. The booster heating unit will automatically turn off when the temperature of the water reaches the thermostat setting. If the water temperature drops below the setting again the booster will re-activate.

In-Series Gas Boosting

An in-series gas booster (also known as a continuous flow gas booster) can be installed between the solar water heater and the hot outlets in the house. This booster should be permanently active. The booster senses the temperature of the water passing through it: if the water temperature is above its temperature setting it does nothing; if below it will automatically heat the water up to the preset outlet temperature setting. This gas booster ensures hot water delivery for a variety of hot water demands without the need for user intervention while enabling maximum solar energy contribution to the water heating. For more information on this booster, consult the owner’s manual for the product.

Over-Temperature Protection System

The Open Circuit Series systems may be installed with a ‘TRV’ located between the cold inlet of the tank and the cold inlet of the collectors. This valve restricts the flow through the collectors when the tank has reached a sufficiently high temperature.


Why Solahart Solar Hot Water Systems: Download

Solahart 181L Solar Hot Water System Brochure: Download

Solahart In-Line Gas Booster Brochure: Download

Installation Manuals

Solahart On-Roof Solar Hot Water System Owner's Guide and Installation Manual: Download

Solahart In-line Gas Booster Owner's Guide and Installation Manual: Download

Solar Incentive Forms

Small-scale Technology Certificate Assignment Form: Download