Compact Thermosyphon Solar Water Heater with Low Pressure



MODEL Absorbing Area vacuum tube Tank
(m2) diameter length No. (L)
ECO-420-1500/47-16 0.8 Φ 47mm 1500mm 16 88 66/137
ECO-420-1500/47-18 0.90 Φ 47mm 1500mm 18 100 56/115
ECO-420-1500/47-20 1.00 Φ 47mm 1500mm 20 112 50/105
ECO-420-1500/47-24 1.20 Φ 47mm 1500mm 24 135 44/92
ECO-470-1800/58-18 1.44 Φ 58mm 1800mm 18 150 39/81
ECO-470-1800/58-20 1.60 Φ 58mm 1800mm 20 165 35/73
ECO-470-1800/58-24 1.92 Φ 58mm 1800mm 24 200 30/62
ECO-470-1800/58-30 2.40 Φ 58mm 1800mm 30 250 24/50


All glass vacuum tube non pressure solar water heaters rely on the natural circulation of water between glass tubes and the tank. As water in the vacuum tubes is heated and rises naturally into the tank, while cold water in the tank flows down to the bottom of the vacuum tubes, causing circulation throughout the system.

All glass tube non pressure solar water heaters characters:

1. Stable, reliable solution, easy installation and scientific structure, elegant, natural and beautiful.
2. Solar Vacuum Tube made from hard borosilicate glass with unique coated layer, high efficient with twin-glass solar tubes.
3. Inner water tank is made of SUS 304 2B 0.41mm food grade stainless steel, which provide long-term corrosion resistance. Water is pure and drinkable. Outer tank is made of 0.31mm colour steel.
4. Heat insulation layer: 50 mm polyurethane integral foaming, superior heat preservation, keep water hot for 72 hours.
5. Between vacuum tubes and inner water tank, we adopt silicon rings to connect and seal them.
6. Controler is optional, so system is automatic to fill in cold water.
7. High solar-thermal conversion and low heat loss.
8. Auxiliary electric booster 1500W is optional, ensure 24 hours hot water.

Freezing is a concern for any solar water heater, but with our system, mild sub-zero temperature is not a major problem. The solar tubes are very well insulated (vacuum), as is the tank (50mm polyurethane insulation). Furthermore, the tank is full of warm or hot water. It would take several days of weather day and night to freeze the water. Also ice floats and so would not form in the evacuation tube, but on the surface of the water in the tank.
As long as there is some sunlight during the day, the water temperature would increase and preventing freezing at night. If you have sub-zero temperatures day and night and no sunshine, then it might be necessary to empty the system of water (including the water in tubes) for such periods each year.

The advantage of solar tubes is that they insulate the inner tube form heat loss. This means once heat is absorbed, it is transferred to the water in the tube, and not lost to the out environment. Because the water is in direct contact with the inner glass tube the heat transfers very well. The performance of the tube itself can reach 80%, but because of the heat losses of the tank, the total system efficiency is around 70-75%(depends on ambient temperatures)

We all know that salty water is also corrosive. In order to provide maximum corrosion resistance,we use the high grade 304-2B stainless steels. The use of an optional magnesium sacrificial anode will greatly prolong the life of the tank by protecting against corrosion. The anode may be changed every 2-3 years (depending on water quality) to provide continued protection.

In order to combat scale you may:
1. Use electric or magnetic water –softener on you plumbing line.
2. Use solar water heater in combination with a water softener.

The solar water heater is virtually maintenance free. If the tubes are very dirty they may be washed with warm soapy water and a soft cloth, or blasted with high-pressure water. Upon normal use no other maintenance is required.
If a tube should ever be broken it will only take a few minutes to replace.

Our solar water heater are divided into two size categories;
47-1500 series and 58-1800 series

47-1500 mm series are suitable for areas with high insolation levels (annual average of >4.5kWh/m2/day), or for areas where hot water can not be used everyday. 58-1800 mm series are for areas with lower insolation levels. It is not advised to install a B model in areas with high insolation levels, unless hot water is used frequently throughout the day for more than one day in strong sunlight the water will boil, resulting is wasted energy and evaporated water.