Unvented
hot water storage systems remain to be a popular choice for several
applications, including offices, schools and hotels. However, while they are
often installed out of sight, they shouldn’t be out of mind, and need to be
kept clean to ensure a reliable and efficient hot water supply is maintained.
Carrying out any cleaning procedures as part of an annual maintenance
schedule will be sure to reduce ongoing maintenance costs by improving the efficiency and longevity
of the system.
George Linder, Product Manager of Cylinders at Heatrae
Sadia, outlines three key considerations to keep an unventedhot water cylinder clean and performing as it
should.
Water composition
It’s vital
to consider the local water composition when installing an unvented system, as
it can affect the system’s performance. Let’s take chloride levels for example,
where high levels can essentially attack stainless steel with its corrosive
properties, potentially exposing cracks and leaks in pipework and the cylinder
itself.
Water
hardness goes hand-in-hand with scale deposition and the level of suspended
particles in a system, which may require filtration to remove. It’s also worth
noting that most pressure reducing valves will include a strainer mesh to
prevent particles impairing the operation of the valve. However, it’s important
to inspect and clean the strainer on at least an annual basis during any other
maintenance checks.
Water treatment
Depending
on local conditions and end-user requirements, installers will need to
recommend specific water treatment techniques to keep a system free from
contaminants.
- A filtration system will ensure
water is treated before it enters the hot water cylinder, preventing the
build-up of limescale within the system and on heating elements.
- Ion exchange water softening
works by extracting hardness minerals in water which are causing limescale
(such as calcium and magnesium) and replacing them with sodium minerals to
soften the water.
- Another consideration is water
conditioning, via chemical or non-chemical alternatives including
electronic or magnetic water conditioning.
Control of bacterial growth
A tank can
be well-designed and compliant but if it’s installed in a poorly designed
system, there can still be problems with bacterial growth.
Luckily
though, control of bacteria growth can be achieved thermally. For example, if
the water is being stored at a temperature above 60°C, it should be circulated
at a temperature below 55°C, and delivered at a temperature above 50°C.
However, safe delivery temperature requirements shouldn’t be forgotten, as
water delivered above 52°C will scald. Bacterial growth can also be controlled
chemically via disinfection or UV treatment. However, this option is usually
more expensive and only applied in large commercial installations.
Ultimately,
to ensure the continued optimum performance of an unvented cylinder, it should
be regularly maintained and kept clean, not least in hard water areas or where
the water supply contains particulate matter. In all instances though, good
system design practice and sizing in accordance with approved guidelines is
required.
To register for our CPD course on unvented hot water
systems, please visit www.heatraesadia.com/specification/cpd
