Hot Water Cylinder

A standard hot water cylinder, i.e. one not connected to a solar system, will have one coil inside it that acts as a heat exchange for the hot water from the boiler. This is known as a single coil cylinder.

For a solar system, the existing single coil cylinder must be replaced by a dual coil cylinder. These are commonly narrower and taller than single coil cylinders as this allows for better stratification of the water. Because you want the solar system to do most of the work, the bottom coil is the heat exchanger for the solar system, and the top coil is the heat exchanger for the boiler. The cylinders come with factory fitted insulation to increase the efficiency of the system.