BSEE BOILERS & HOT WATER
n traditional atmospheric water heaters the gas burners are located below the cylinder, making them susceptible to scale dropping and settling to the base of the unit. This creates an insulation barrier to the heat source and affects the
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efficiency of the unit. Just a 1mm build-up of scale can reduce the efficiency by 7.5%. This can also cause excessive expansion of the heat transfer plate which can result in cracking ending the water heater’s life.
Hot water systems must be designed and maintained to ensure they deliver safe and efficient hot water. But to comply with regulations and gain maximum operating efficiency you need to be aware of the water quality, understand the effects of scale and adopt a tailored water treatment regime that is relevant to the type of system, location, application, and hardness of the water, writes Kevin Potter, Business Development Manager – Hot Water Solutions, Hamworthy Heating.
An accumulation of scale in a hot water system can reduce the inside diameter of water pipes or block them completely. This will affect the water pressure and flow within the distribution circuit, increasing the work and energy required for pumps.
The presence of scale in the system also provides the right conditions for the proliferation of legionella bacteria.
Why do anything about it?
Providing safe hot water is the most important reason for maintaining a clean system, but cost and efficiency are also important – particularly as running costs are ever increasing and Government targets and regulations are getting stricter. The more scale present in a system the more energy used and thus more CO created.
Prevention is much better than cure and normally cheaper. Ensuring hot water systems are clean and serviced regularly helps maintain efficiency and longevity of appliances and keep running costs to a minimum.
An unplanned maintenance cost as a result of untreated water can lead to system down time. If it is critical hot water supply, such as healthcare premises, schools and hotels, then it can lead to closure of the premises. An unbudgeted distress purchase usually rushes to
replace equipment like for like rather than reviewing the system and seeing where changes and improvements can be made for greater efficiency now and in the future.
What can you do to reduce scale?
Physical water conditioners alter the physical structure of hard water crystals, making them easier to dispose of, without the use of chemicals.
‘ Prevention is much
better than cure and normally cheaper. Ensuring hot water systems are clean and serviced regularly helps maintain efficiency and longevity of appliances and keep running costs to a minimum. An unplanned maintenance cost as a result of untreated water can lead to system down time.
In water treated by a physical water conditioner, previously separate positive and negative ions are brought together into clusters of at least one positive and one negative ion. The clusters of ions attract and hold the hardness minerals (calcium and magnesium) meaning that most are discharged with the water. Those that remain form the softer, far less problematic, type of scale that can be easily wiped away.
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Water softeners also work on ions contained within the water. Hard water contains calcium and magnesium ions and water softeners
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BETTER CONTROL, LOWER EMISSIONS Maintaining a safe, efficient hot water system
use resin beads, which hold sodium ions. When hard water passes through the resin beads inside the softener, the beads attract and hold the calcium and magnesium ions and give off the sodium ions. After this ion exchange process, the water leaving the softener is soft. Once the resin bead is loaded with calcium and magnesium ions, salt water is used to wash the resin beads. The salt water solution (brine) loosens the hardness ions which have built up on the resin beads and the system then backwashes and flushes the hardness minerals away. The resin beads, once again hold the sodium ions and the system is ready to soften more water. An ongoing regime is vital for combating scale and lowering the chance of legionella bacteria forming and spreading in the system.
Increase in use of condensing water heaters
Newer models of water heater such as the Dorchester condensing water heaters from Hamworthy Heating are fitted with a down firing pre-mix modulating burner. This eliminates the risk of scale build up impacting on the heat transfer (an issue evident in atmospheric water heaters).
This is just one of the benefits in using condensing water heaters over atmospheric models. We’re seeing more systems specified with condensing units – namely due to the increase in regulations and greater efficiencies possible from these units.
With heating loads getting smaller it is often now the case that a higher percentage of energy in a
commercial building will be used for hot water.
The introduction of the Energy Related Products Directive (ErP) last year tightened efficiency levels for many products that use energy. The impact of ErP for hot water appliances will be phased in using several stages up to September 2018, at which point higher efficiency condensing products will become the norm.
Although the impact of these regulations will eventually force people to switch to condensing water heaters it also makes good economic sense. The ease of integration with condensing boiler systems, as well as all the associated benefits of increased efficiencies, better control, lower emissions and lower running costs will all help to provide customers with the safest and most efficient hot water systems.
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The introduction of the Energy Related Products Directive (ErP) last year tightened efficiency levels for many products that use energy. The impact of ErP for hot water appliances will be phased in using several stages up to September 2018, at which point higher efficiency condensing products will become the norm.
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www.hamworthy-heating.com
uA build‐up of scale at the bottom of a water heater.
14 BUILDING SERVICES & ENVIRONMENTAL ENGINEER APRIL 2016
uThe condensing water heaters and storage tank from Hamworthy Heating meet the large peak demands for showers at the University of Nottingham sports pavilion.
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