A solar cylinder is used in conjunction with solar panels and they convert energy collected from the sun's rays to heat a water/glycol liquid in its pipe work. This liquid is circulated through a specially designed solar coil in the base of the cylinder where the liquid transfers its heat to the water stored before being pumped back to the solar panel to be reheated. The design of this coil allows maximum solar gain to be achieved ensuring that the solar system is being used to its full potential. The second coil, fitted further up the cylinder is coupled to the building’s principal heat source, usually the central heating boiler.