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Solar water heater plans and designs

Solar hot water heater plans, designs and system components

There are solar water heater plans and designs that can be very suitable for a DIY installation. Whether you're considering purchasing a pre manufactured system or you're referencing several plans and designs for a DIY installation, understanding how the primary and secondary components in these system's work will be vital.

Types of solar water heater designs

Solar water heater plans and designs can vary from basic and simplistic to very detailed and complex. All system plans and designs can be classified as either passive or active plans.

Before taking on or even considering a DIY installation, it would be wise to further familiarize yourself with the differences in passive and active designs, and decide which design type best suits your consumption needs and regional climate.

Major design components

All solar water heater plans, whether simple or detailed, are centered around the designs' major components. Whether your considering a DIY installation or your attempting to tailor design a system, most of these major system components will be incorporated into the solar water heater design.

  • Solar Hot Water Panels; are the heart and soul of a system, collectors are responsible for harnessing the sun's free and renewable thermal energy.
  • Solar Hot Water Tanks; enable the system to provide hot water on demand and at times when the sun's thermal energy is unaccessible.
  • Solar Hot Water Pump; is required in many solar water heater plans in order to circulate the fluids through out the system.
  • Solar Heat Exchanger; this major system component provides a substantial amount of freeze protection, which will be required in many climate regions.

Additional components required in all plans and designs

Back Up Water Heater

With the exception of single tank solar water heaters, a back up heating source is absolutely required. The presence of a back up source further ensures that there's hot water rain or shine and day or night. Conventional storage tanks or tankless hot water heaters are the most often used back up source.

Temperature Pressure Relief Valve

A temperature pressure relief valve should be installed at the hot water outlet of the solar water panel. This plumbing valve releases excess water from the outlet of the panel.

The release of excess hot water avoids a very dangerous build up of pressure in the panel, or collector. A pressure temperature relief valve is an important safety feature that's required by just about all plumbing codes.

Tempering Valve

The tempering valve is another safety feature and a must have in all solar water heater plans. It's plumbed at the very end, after the back up heating source. A tempering valve mixes hot and cold water when the outlet water temperature is too high, avoiding scalding hot water from ever entering the indoor fixtures.

Solar Bypass or Isolation Valve

This valve is required in solar water heater plans to ensure an adequate supply. The solar bypass valve isolates the solar hot water storage tank in the case of an emergency, allowing the back up power source to take over and supply hot water. This valve can also be manually turned, allowing the sun to provide 100% of the daily hot water load during the sunniest and warmest times of the year.

Additional components required in active plans and designs

Heat Transfer Fluids

Heat transfer fluids are used to protect the system from freeze. More times than not either distilled water or an antifreeze solution is used. In plans that require an antifreeze solution, propylene glycol is most often used.

Distilled water is simply boiled water that's condensed. Boiling and condensing removes all the mineral impurities that can potentially damage all the metallic components within the loop.

Propylene glycol is a non toxic antifreeze solution that contains anti corrosion additives. Solar water heater plans and designs that use propylene glycol may have the added flexibility of incorporating a single wall solar heat exchanger.

Differential Thermostat Control

A differential thermostat control is always required in solar water heater plans and designs that contain an AC solar hot water pump. This control activates the AC powered pump when the panel (or collector) temperature is hotter than the domestic water in the storage tank.

The differential thermostat control uses temperature sensor readings from both the hot water panels and the storage tank to efficiently activate and deactivate the system's water pump.

PV Module

A PV module is always required in solar water heater plans and designs that use a DC solar hot water pump. The PV module is a small photovoltaic panel, or solar electric panel, that's wired to the pump.

This control doesn't use sensors like a differential thermostat control, instead PV modules gauge the intensity of the sun. When the sun is shining bright, the PV module activates the system's water pump and vice versa.

Drainback Tank

A drainback tank is required in all drainback solar water heating systems. When the heat transfer fluid is not being circulated throughout the system, the fluid is designed to collect in the drainback tank.

These tanks are relatively small, ranging anywhere from 6 gallons to 15 gallons in volume. In drainback solar water heater plans and designs the drainback tank should always be installed above the panel, or solar collector. Larger drainback designs will naturally require larger drainback tanks.

Expansion Tank

An expansion tank is a must have in any closed loop solar water heating system that uses antifreeze solution as a heat transfer fluid. The expansion tank serves as a storage facility for the extra fluid volume in the solar loop.

This is required because the antifreeze solution will expand when it's introduced to extreme heat. The expansion tank is an important safety feature, without it every major component in solar water heater plans that incorporate antifreeze will be seriously compromised.

These tanks should be sized to hold up to 40% of the antifreeze solution before expansion. But going with a larger size will only provide more insurance. These tanks generally range in size, usually anywhere from 2 to 4 gallons in volume.

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