EcoSolar Energy Conscious Design Limited
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Cylinders
There are many options for hot water cylinders.
Low pressure
Low pressure copper cylinders offer a good resilience to high water temperatures as experienced in
solar water heating systems and are historically proven for most areas. There are several areas in New
Zealand that suffer from poor water quality and this can result in a significantly reduced life
expectancy.
Many households now insist on higher water pressures and this limits the number of low pressure
cylinders being installed.
Medium pressure
Medium pressure copper cylinders offer a good resilience to high water temperatures as experienced
in solar water heating systems and offer increased resilience to poor quality water than low pressure
cylinders. Medium pressure cylinders provide a good reliable cylinder at a lower price than mains
pressure cylinders whilst offering increased water pressures over low pressure cylinders. In many case
a good compromise. However, again many households now insist on higher water pressures and this
limits the number of medium pressure cylinders being installed.
The low and medium pressure cylinders often offer a reduction in water usage, which is becoming
increasingly important.
Mains pressure
There are now more and more options available for purchasers of mains pressure cylinders, including
steel lined and stainless steel cylinders.
Lined steel cylinders are often the lower cost option for mains pressure cylinders however care
should be taken in their selection for solar water heating systems as many have a relatively low
maximum recommended storage temperature. Temperature limitations of between 70 to 85
O
C are
common. Care should be taken in moving steel cylinders as the internal lining can easily be damaged,
which then exposes the steel cylinder to the stored water.
Stainless steel cylinders, especially duplex stainless steel cylinders appear to have a good resilience to
poor water quality and to the higher water temperatures experienced in solar water heating systems.
However their quality and thus life expectancy is very dependent upon the quality and cleanliness of
the manufacturing process.
Cylinders with / without heat exchangers
Cylinders can be fabricated with or without internal heat exchangers and there are several
configurations available. Unless a heat exchanger is installed, the solar water heating system will
