solar & a standard boiler
With a standard boiler and cylinder additional calculations need to be done to ensure you always have enough hot water. A larger cylinder is used and the top part of the cylinder is connected to the boiler whilst the bottom part is connected to the solar thermal system. This method ensures that there will always be enough hot water even when there is no solar gain.
solar & a combination boiler
Some boilers allow pre-heated water to pass through it before going straight to your taps. With this system, a solar diverter valve is used. If the pre-heated water is at 60 degrees it will go straight through to your taps. However, if the water is below 60 degrees the diverter valve will enable the water to pass though the boiler where additional heat is used to increase the water temperature. This means that even when there has been little solar gain the pre-heated water can be used so the boiler doesn't have to do as much work and, as a result uses less gas.
what are the requirements for solar?
A south facing roof (although an east-west array can be used) The roof can be pitched or flat.
Enough room internally to install the required components
A gas boiler suitable for your type of system
Solar thermal can also be used along side air source/ground source heat pumps and solar PV systems. Solar thermal should last at least 30 years!