When and how to switch to a solar water heater

July 29, 2015

A solar water heater costs more than a conventional system to buy and install, but it's cheaper to run, saving you money in the long term. There's a lot more to consider as well. We'll go over everything and help you decide if switching to solar is right for you.

When and how to switch to a solar water heater

Consider the type of system to install

  • Keep in mind that some storage tanks used with conventional systems will need replacement within 10 years. When considering the switch to solar, take this extra expense into account, and consider investing in a long-lasting tank made of stainless steel or copper.
  • Tanks for mains-pressure systems are manufactured from stainless steel or from mild steel with a glass-like lining of vitreous enamel. The low pressure of gravity-feed systems allows the use of weaker, but corrosion-resistant, solid copper storage tanks.
  • Stainless steel tanks can last more than 20 years. Look for high-quality heat treatment of the welding joins to reduce the occurrence of stress fractures and early failure.
  • A steel, glass-lined, hot-water tank has a life expectancy of between 10 and 15 years. These tanks are fitted with a "sacrificial" anode that's designed to be eaten away preferentially over the steel in the tank. This anode should be taken out, inspected, and replaced if necessary every five years.
  • If the water supply has a high silica or calcium content, the manufacturer should be consulted about possible effects on the system. This could also impact your warranty.
  • Stainless steel reacts adversely to chloride ions in water. Water drawn directly from underground often contains contaminants that can build up and cause blockages.

Keep these points in mind

  • A solar hot-water system must collect as much of the sun's heat as possible. This means that collector panels may have to be held on a galvanized frame if the pitch of the roof is too low. When placing the panels, always try to avoid shading from nearby trees and buildings.
  • All pipes should be insulated, especially those on the outside. Pipes should also be kept as short as possible. The further the water has to travel, the more heat it will lose in transit.
  • Check that your roof is strong enough to support the weight of a hot-water system. A 300-litre (315 quart) tank holds 300 kilograms (660 pounds) of water. A normal trussed roof is designed to support the weight of the roofing material only and may need to be strengthened. Wherever possible, place the tank over a load-­bearing wall.
  • Even in the sunniest regions, solar hot-water systems require occasional boosting by conventional power. This generally involves an electrical element connected to a time switch so that it operates at off-peak periods whenever possible. Gas-fired boosters must have a control system that stops ignition when there's sufficient solar input.
  • A slow-combustion stove can provide an energy-efficient backup on cloudy days. You can connect a gravity-feed hot-water system directly to the hot-water jacket of the combustion stove.

Solar power is cheaper and more environmentally friendly than traditional energy sources, which makes switching an easy choice. Simply follow this guide and make all of the necessary considerations so that you can start enjoying the benefits of solar.

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