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Considerations When Choosing a Solar Hot Water System

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Considerations When Choosing a Solar Hot Water System

Choosing what kind of solar hot water system to buy for your home requires careful consideration of climate, size, and position. You also need to know how it will be installed, and what kind of maintenance is required. Then you will be well on your way to saving energy and money. Check out the local Government rebates for installing a solar hot water system in your state.

Climate considerations are very important when selecting a solar water heater and your state government advisory centres can provide excellent local advice. State governments can also provide advice on any rebates that are available in your area.

The Australian Consumers' Association provides detailed information to help you choose the best solar water heater for your location and budget. Manufacturers and retailers may also be able to help with detailed selection guidelines.

The size of storage tanks and solar panels depends on the number of people in the home, how efficiently they use water, the climate and the efficiency of the water heater. Reducing your hot water demand can reduce the size and cost of the system you need. Manufacturers or suppliers will advise the best size for your application.

For optimum performance throughout Australia solar hot water systems should face solar north. Orientation can deviate up to 45 degrees from north without significant loss of efficiency. Use a compass to check orientation.

For maximum efficiency, ensure that the solar collectors are not shaded by trees or nearby buildings, particularly in winter when the sun is low in the sky.

For best performance, solar collectors need to be installed at an angle to the horizontal. This maximises the amount of sunlight falling on the panels. For maximum winter performance, panels should be installed at an angle 5 to 10 degrees greater than the angle of latitude at the site. The ideal angle increases from 17.5 degrees to the horizontal in Darwin to 53 degrees to the horizontal in Hobart.

Roof pitch angles in Australia are commonly between 20 and 30 degrees. It is cheaper and usually more aesthetically pleasing to install solar collectors flush with the roof, rather than use supports to achieve a greater angle. Performance in winter may be slightly reduced, but the benefits usually outweigh the costs.

A complete thermosiphon system, when full of water, can weigh several hundred kilograms. Most roofs can support a storage tank without reinforcement but you need to check this before installation. Talk to your builder, designer or engineer to find out.

Be sure to insulate all components, including pipes, to get the best performance from your system. This is particularly important for thermosiphon systems where there is a long distance between the tank and the hot water taps. It is critical in cold climates.

Make sure the booster control is in an accessible location and has an indicator light you can see from inside to remind you to turn it off when not required.

When operating and maintaining the system, it is best to follow the manufacturer's instructions, as this will be specific to the type and style of the system. Set the temperature of your booster thermostat to about 600 degrees. A lower setting will use less energy but you should stay above 550 to prevent growth of harmful bacteria.

In favourable climates during summer, water temperatures in a solar water heater can approach boiling point. Heat dissipation devices may be required to prevent water from boiling. It may also be necessary to fit a mixing valve to reduce water temperatures experienced at the tap to safe levels during summer.

Carry out jobs that need hot water early in the day so that the water left in the tank will be reheated by the sun, ready for use at night.

Regularly clean solar panels to remove dust. You can use a broom with some detergent to give them a scrub.

Flush out collectors to remove sludge. Heat pump systems do not require flushing.

Make sure you turn the booster off when going on holidays and consider turning it off during summer if conditions are favourable.

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