Must-know facts before converting to solar hot-water systems

Going solar is a cool way to heat your water and lower your energy costs. Whether you're installing a new system or converting a gas or electric one, here's what you should know before you buy.

The prime components of a solar hot-water system are the tanks and collectors. The different types of solar hot-water systems include:

• A close-coupled system where the storage tank is adjacent to the collector panels and is usually mounted on a roof. Hot water circulates­ naturally­ on the thermosiphon principle: water enters the collector's lower header, is heated by the sun and rises naturally through narrow-diameter tubes, then flows out of the collector­ into the top of the storage tank. At the same time, cold water flows in to take the hot water's place. This means that there are no moving ­parts.
• A remote-coupled thermosiphon system, which is generally a gravity-feed unit. The tank is placed away from the collector panels, either within the ceiling space or in a cupboard at a lower level. A header tank, which regulates the water supply to the main tank, is attached to the main tank or situated not far above it.
• A pumped system is installed if it is impractical or unsightly to have the tank above the collector panels. Because the tank is at a lower level, water cannot circulate­ naturally, so it must be forced through the system by a small pump. This arrangement is also used when a conventional system is converted to solar.

There are two methods a tradesperson can use to connect your existing electric or gas hot-water systems to solar panels.

Ground-level, mains-pressure systems can be fitted with a special valve to the cold-water inlet to divert water to the panels on the roof.

• Suitable for electric-boosted systems
• Requires a pump and a controller
• Sensors start the pump when conditions are suitable
• If insufficient heat is being collected, the inlet water goes straight into the tank
• To be safe, consult your local gas authorities before reconnecting gas appliances

Solar pre-heater systems can connect to an existing gas storage heater.

• Water heated by solar panels travels to a tank where it is heated by gas to a usable temperature
• For gravity-feed systems, the tank can be fitted with the necessary connections and raised higher in the roof so you can install your collector panels below the tank
• Can also be pump-circulated, but the header tank must be above the panels

Whether you're updating your current heating system or starting from scratch, knowing the components of solar hot-water systems will get you off on the right foot. The next step is a more energy-efficient and eco-friendly home.