Thermosyphon systems work with the natural laws of circulation - hot water rises and cold water sinks.

As the water in the collector is heated, it rises naturally into the geyser, while the cooler, heavier water in the geyser flows down to the bottom of the collector, causing circulation through the system. To achieve circulation during the day and to limit reverse circulation at night, the water tank/cylinder must be above the collector.

Thermosyphon systems can be freeze-resistant. Anti-freeze valves and built-in freeze resistance can be used by placing a closed circuit between the collector and the geyser. This means a heat transfer fluid will be used.

Natural convection systems are mainly used in houses where the water tank can be installed at a higher level than the collector, either inside or on top of the roof. This type of system works best if installed in houses with roofs pitched higher than 15º. Roofs with a lower pitch will still work, however the overall effectiveness will just be decreased although additional inclined support frames can be supplied.

Typical thermosyphon installations use a close-couple configuration. This means the solar water tank and the collector will be in close proximity to each other, with the solar tank higher than the collector.

The tank can be placed inside your roof, as long as it remains above the level of the collector.

Thermosyphon systems can be either close-couple or split systems.

Close-Coupled System
In a close-couple system, the solar geyser and collector are mounted externally and close together. In thermosyphon circulation a close-couple system is very reliable if installed properly.

Split System
In a split thermosyphon system the solar geyser and collector are separated with the geyser usually installed in the roof. The geyser must be above the collector with connecting pipes rising smoothly. The pipes should not level out or dip at any point, as this could cause poor circulation.