Solasyphon - How it works Pressurised Sustem (see right)
  • Secondary cold feed connection to hot water storage cylinder using injector Tee
  • Willis Solasyphon
  • Thermosyphonic flow circulates hot water to hot water storage cylinder where it stratifies at top of cylinder, stored at high temperature and available for immediate use.
  • Pump control unit for solar circuit
  • Temperature sensor
  • Secondary flow
  • Primary solar flow
  • Primary solar return
Diagram of Solasyphon


External Add on

The Solar Syphon system is a simple ‘Add-on’ heat exchange unit, similar in concept to the Willis Immersion heater. The basic premise of the unit is to provide a lower cost installation alternative to traditional twin coil solar cylinder.

Novel heat exchange arrangement

The system is connected directly to the solar collector flow and return loop and through a novel heat exchange arrangement augmented by direct high and low connections made to the existing storage cylinder.

Thermosyphonic action

This is induced between the top and bottom of the cylinder, thus promoting rapid thermal stratification in the cylinder when solar input is realised. The diagram opposite illustrates the working details the unit in a typical installed position.

Other Systems

Click here to see vented system