Australia's most advanced range of Solar Hot Water and Heat Pump Hot Water Systems Australia, New Zealand and the South Pacific
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Good reasons to choose Envirosun


You’ll have the latest technology

The individual components that comprise our systems are sourced from some of the largest and most progressive global producers – it’s what allows us to stay in touch with the world’s best.


You’ll save more energy for longer

Our systems are accredited to international quality standard (ISO 9001), comply with the Australian and New Zealand design standards (AS/NZS 2712) and are registered by the Australian Government Clean Energy Regulator (CER) – it’s your assurance of quality and performance.


You’ll never be without hot-water

Our national network of authorised installers and technicians are trained and equipped to the highest standards – they’re ready to give you the help and advice you need and as fast as you need it. Our extensive range of system sizes, outputs and configurations is designed to suit a wide variety of applications – we’ll have the water heater that you need.


You’ll have the right system at the right price

Our focus is on supplying the most up to date, cost-effective and environmentally responsible water heaters – it’s all we do and we do it without compromise.


You’ll get our full attention

Our focus is on supplying the most up to date, cost-effective and environmentally responsible water heaters – it’s all we do and we do it without compromise.

Thermo Siphon Range

passive solar hot water systems

our TS Systems

Passive, thermosiphon systems

The Envirosun ‘TS Range’ of thermosiphon or passive solar hot water systems offers maximum efficiency and a cost-effective solution for most applications.

Thermosiphon systems feature the traditional ‘tank-on-the-roof’ configuration – an arrangement that was first deployed and commercially marketed around 1909.

The operating principle of these early systems is no different to that upon which a modern-day Envirosun system relies: water in a flat plate solar collector is heated by the sun and the water rises into an insulated storage tank located above the collector … but that’s about all that our modern systems share with their technological predecessors.

Today’s Envirosun TS systems represent the cumulative advance of over a century of technological development. We offer tanks manufactured in either vitreous enamel-lined steel or 444 stainless steel. Our systems are larger, save more energy, deliver more hot-water and do so at a far higher pressure.

To learn more about our TS systems read about our collectors, our tanks, our connections and our back-ups.



The Envirosun ‘AS Range’ of pumped or active solar hot water systems offers greater flexibility, improved aesthetics and higher capacity.

Active systems only require the solar collectors to be installed on the roof with the storage tank situated at ground level or any other convenient and out-of-the-way location. The operating principle of these systems is relatively simple – when the solar collectors are able to add heat into the storage tank, a small pump is switched on to circulate hot-water from the collectors and replace it with cool water from the tank. Once the tank is full of hot-water, the pump is switched off, but ready for the next cycle.

While pumped systems have been around for many years, modern electronics and materials have brought improvements in both function and reliability. Today’s Envirosun AS systems adopt many of these technological advances and blend them with our collector technology, to create our range of high-performance active solar hot water systems.

To learn more about our TS systems read about our collectors, our tanks, Our pumps and controls and our backups.

Active Siphon Range

active solar hot water systems

our solar collectors

Flat-plate collectors

Our solar absorbers receive more solar energy

Unlike conventional glass that soaks up a significant amount of solar radiation, the glass cover on an Envirosun solar collector allows over 90% of the sun’s radiation to reach the solar absorber. We use a low-iron, high-transmittance glass cover which means that there’s more energy available to create more hot-water. And to ensure they keep working for longer, our glass covers are toughened to protect against breakage. To find out how low-iron glass improves the optical properties of a solar collector cover, read: our solar glass.

Our solar collectors convert more solar energy into useful heat

Envirosun absorbers are coated with a high-performance black-chrome treatment to create a surface that absorbs more and emits less solar radiation. To find out how black chrome works to dramatically improve the performance of a solar absorber compared with black paint and other surfaces, read: Our absorber surface.

Our solar collectors are designed to last

The absorbers are manufactured using high-quality copper for both the riser tubes and the absorber plate. Copper resists the effects of corrosion on the inside and outside of the absorber. The collector trays are produced from aluminium, a material renowned for its strength and ability to withstand extremes of weather. Copper and aluminium together – the reason you can be assured of a long service life from your Envirosun solar collectors.

our hot water tanks

Durable pressure vessels

Our storage cylinders are built to last

Envirosun TS tanks are fabricated from high-strength materials especially suited to operating in high-temperature, high-pressure applications which can otherwise be very corrosive. And for added life our TS Plus tanks exclusively incorporate 444 stainless steel internal pressure vessels. To learn about our 444 stainless steel tanks, read: our stainless steel.

Our hot water tanks stay hotter for longer

Envirosun cylinders are encapsulated in a pressure-injected, high-density polyurethane thermal insulation. Compared with archaic insulation systems using straw, wool or fibreglass, polyurethane retains more heat and does so for far longer – and it has the added advantage of imparting structural rigidity to the assembled vessel. To find out how polyurethane is used to create a superior thermal barrier, read: our insulation.

Our storage cylinders deliver hot water faster

Our storage cylinders deliver hot water faster Our solar hot water systems are rated to operate high water pressures that are near to that of the mains water supply. Unlike low pressure hot-water systems, you can enjoy plenty of hot-water from more than one outlet at the same time. To understand how our system of pressure control valves works to limit but maintain hot-water system pressure, read: our pressure valves.

Envirosun systems use this mix of optimisation and over-temperature protection functions to maximise energy savings and minimise heat stresses.

Advanced solar water heating technology

Our unique approach to making solar hot water systems is part of what makes them so advanced.

We’re agile:

we keep a watching-brief on international advances and absorb the best of these trends into our products.

We’re nimble:

we avoid getting locked-in to capital-intensive equipment that may otherwise take away our flexibility to implement these advances.

And we’re forward-looking:

we think about what our customers are looking for today and tomorrow and advance our own designs to meet these demands.

our solar glass

Durable pressure vessels

Our collectors are fitted with solar glass that is highly translucent and very strong.

It’s intended as maximising the amount of solar energy that is captured by the collector absorber plates while protecting them from impact damage. To explain, this, it’s first necessary to understand how a solar collector uses the ‘greenhouse-effect’ phenomenon to heat water.

The sun’s rays that fall on the glass cover are a form of short wavelength radiation. Most of the solar radiation passes through the glass but some is reflected or absorbed. The transmitted portion of solar radiation that reaches the black absorber plate heats it and the water that is contained inside. The hot absorber also re-radiates thermal energy (a form of long wavelength radiation) which, in the absence of a cover, would escape and allow the plate to cool. The glass cover, however, acts as a reflector of the long wavelength radiation and bounces it back to the absorber, thereby containing the heat. Glass that has higher iron levels absorbs more solar radiation and allows less to reach the absorber plates. Low-iron glass can transmit about 91% of the incident solar radiation. Envirosun solar glass is produced with very low levels of iron impurities. Envirosun solar glass is also tempered using a heat-treatment process.

our absorber surface

More heat than light

The absorber plates in our solar collectors are designed to absorb more of the sun’s energy and radiate less back to the environment as heat.

To achieve this they undergo a two-stage electroplating process. They are first plated with a layer of bright nickel and then re-treated with an over-coat of black chrome. This creates a ‘spectrally-selective surface’ that absorbs more solar radiation and re-emits less thermal energy. The underlying mechanisms are relatively simple. In the short wavelength part of the spectrum, the absorber behaves like a black surface and soaks up most of the sun’s energy. In the long wave length part of the spectrum, the absorber behaves like a silver surface and re-radiates little of its heat.

Envirosun black chrome absorbers are amongst the most efficient solar selective coating available and deliver performance gains about 20% above those available from non-selective treatments.

our stainless steel

A silver bullet

Envirosun pioneered the use of Type 444 ferritic stainless steel in the construction of hot water system pressure vessels.

Compared with traditional austenitic stainless steel (such as Type 316L and 304L) ferritic stainless steels offer major performance advantages. In particular, Type 444 out-lasts Type 316L when it comes to resisting localized corrosion or pitting attack at elevated water temperatures.

Generally, Type 444 is a highly durable and trouble-free material that offers significant live cycle cost advantages. Stainless steels derive their corrosion resistant properties through the inclusion of stainless steel. However the key to the enhanced performance of Type 444 is the addition of molybdenum and chromium as further alloying elements (traditional austenitic grades incorporate nickel). During the final stage of the factory guarantee period we can arrange for an end-of-warranty service and an extension to the warranty cover.

Choose an Envirosun TS Plus hot water system using Type 444.

our pressure valves

Keeping the pressure on

The speed that a hot-water system can deliver water to the hot taps is mainly dependent on the pressure at which the system operates.

Low pressure hot-water systems that were once very prevalent and some forms of electric instantaneous systems that are still used today often cannot effectively deliver hot-water to more than one tap at once.

High pressure hot-water systems avoid these constraints but they must be protected with appropriate pressure control valves to ensure safety and longevity. Envirosun solar hot water systems are fitted with three levels of pressure control. First, the inlet pressure is reduced to 450kPa. This represents the minimum pressure at which the tank will deliver hot-water. Second, there is a cold-water relief valve that operates at 600kPa – this represents the normal operating pressure of the tank. The purpose of the cold-water relief valve is to relieve excessive pressure that will otherwise build up in the tank due to thermal expansion of the water. Because the relief is connected to the bottom of the tank, no hot water is lost in this process.

Third, there is a hot-water relief valve that operates at 700kPa or when the tank temperature reaches 99oC. This valve is provided as a secondary level of safety and will only operate as a pressure control valve if there is a problem with the cold-water relief valve.

our insulation

It’s hot on the inside

Keeping the heat on the inside of a hot water system storage tank is a major aspect of saving energy and operating costs, and polyurethane insulation systems are the best way of doing this.

Polyurethane is formed through the reaction of two chemical liquids with the mixture then injected into a contained space. As the mixture is exposed to air, it expands to up to 10 times its liquid volume. In so doing it fills all of the contained space including the smallest of crevices. As the mixture dries it hardens to form a closed-cell structure that is a rigid and impermeable structure. Compared to fibreglass insulation that allows air to permeate, polyurethane is airtight. The resulting insulating barrier works at three levels: the gases trapped in the cells resist conductive heat losses; the air-tight structure prevents convective heat loss otherwise caused by the flow of warm air to the cooler surrounds; and condensation heat loss, normally caused as warm air is introduced to cold air, are avoided.

The hot water cylinders of all Envirosun storage tanks are encased within a polyurethane foam insulation system. The polyurethane mixture is pressure injected into the space between the cylinder and the external sheet metal casing.

The combination of metal and foam contributes to structural rigidity and is the basis of its excellent heat retention properties.

our pumps & controls

Information is power

The Envirosun AS Range of solar hot water systems uses a small circulating pump and electronic microprocessor to transfer the heat absorbed by the solar collector to the separate storage tank.

The circulating pump draws very little electrical power (less than 28 watts) and only operates when the microprocessor determines that there is a useful gain to be made.

The microprocessor takes information from temperature sensors on the solar collectors and in the storage tank. When the collectors are 6°C hotter than the water in the storage tank, the circulating pump is operated. When the differential falls to 4°C or lower, the pump is not operated. The microprocessor also uses the sensor information to control a suite of over-temperature protection modes:

  • if the water in the storage tank reaches 70°C, the pump is stopped;

  • if the collector temperature reaches 190°C, the pump is cycled on to control the temperature to below 185°C;

  • if the collector temperature reaches 200°C the pump is not operated;

  • if the tank temperature has risen above 70°C and the collectors are cooler the pump is run.

our backups

Never be without

Running out of hot water is no longer a problem with gas or electric boosters ensuring your shower is hot from start to finish.

Envirosun solar hot water systems are fitted with either electric or gas boosters to ensure that there’s plenty of hot-water available during the worst weather or when the demand is the highest. Electric elements can be fitted inside or storage tanks or the gas heaters can be installed in-line from the outlet of our systems. Both options are designed to maximise the amount of solar energy that can be collected and utilise the auxiliary in a ‘back-up’ or ‘booster’ mode only.

Electric boosted systems are integrated arrangements that comprise a heating element immersed in the storage tank water, controlled by a thermostat and connected to a switched power-supply. Both the element and thermostat are positioned at the midpoint of the tank and the power-supply switch is conveniently located. With the power-supply on, if the temperature at the centre of the tank falls below 60°C, the thermostat ‘closes’ and the heating element operates. The element continues to operate until the mid-point of the tank rises to above 60°C. The location of the element and thermostat in an Envirosun system are designed to only allow the booster to only heat the water in the top half of the tank and to leave the bottom portion available for useful solar gain.

Gas boosted systems involve a continuous-flow gas water heater that is mounted separate from the storage tank. The outlet from the solar hot water system is piped as the inlet to the gas heater. If the water reaches the gas heater at a temperature below 60°C, the gas supply is opened, the spark-ignition system fires, and the gas burner operates. If the inlet water temperature is above 60°C, the gas heater does not operate.

Envirosun systems use this pre-heater configuration to achieve higher solar contribution and significantly lower greenhouse gas emissions.

our connections

Staying close to the action

Envirosun TS tanks sit on the roof immediately above and butted against the solar collectors.

This reduces the amount of piping between the tanks and collectors that is transporting hot-water and therefore reduces the chances for heat loss. Compared with systems where the tank is located remote from the solar collectors, the Envirosun configuration ensures more heat ends up where you want it – inside the storage tank.

Close-coupled, thermosiphon solar hot water systems are amongst the simplest, most reliable and most efficient solar water heaters. For best results, the bottom of the storage tank is located above and immediately adjacent to the top of the solar collectors. As the water in the collectors is heated by solar energy, it rises through a connecting pipe to a point mid-way up the storage tank. This displaces cool water in the storage tank that travels through a pipe connected between the low-point of the tank and the bottom of the collectors.

If the collector temperature falls to below that of the water in the tank, circulation stops automatically. The whole process occurs without the need for any external power to operate pumps or valves – and the flow rate between the tanks and collectors is automatically optimised because it is a function of the temperature differential between them and the solar energy that is available.

Finally, because the distance between the tank and collectors is very short, the opportunity for transport heat losses is extremely low compared with configurations where the tanks and collectors are remote from each other.

Envirosun close-coupled solar hot water systems can represent the most cost-effective option.