Burning issue
Examining the options to a high-scale problem
Stored hot water systems suffer badly from the problem of scale build up – even when water treatment measures are set in place which could put a burden on water heaters. Scott Humphries argues in favour of zinc-based calcium inhibitors
consists of calcium carbonate (calcite) with lesser amounts of other calcium salts such as the sulphate. Sometimes limescale deposits contain corro- sion debris and this scale build- up can affect the water heaters by reducing their efficiency and overall performance. Ultimately, ongoing use with hard water will shorten the lifespan of water heating appliances.
Limescale build up is a serous problem in Southern England, Wessex, Wales, Hull and the Thames area. In these hard water areas especially scaling in stored hot water systems ultimately leads to lower performance, breakdown, and expensive reme- dial treatment such as power flushing and in the worst sce- nario cracked cylinders. Serious money has to be then spent to get the system back to work; all of which means downtime, inconvenience and, for many businesses a detrimental impact on income.
Basically there are three types of water treatment available for the management of scale. The first, a calcium softener, physical- ly takes calcium out of the water and exchanges it for sodium. The second type is a physical electro magnetic device that clips around pipe work and encourages the scale to ‘go with the flow’ rather than affix itself to the cylinder. Sodium water softeners are
effective but have two draw- backs – the water is not potable and they rely on people to put salt in them, thereby allowing a large margin for human error. One of the most common rea- sons for engineers to be called out is because ‘the water soften- er has stopped working’. Ninety nine times out of a hundred this is only because the operator has forgotten or omitted to add salt to the water conditioner. The
10 | July 2014 | HVR
A Rinnai Infinity PLUS storage system
third solution, zinc based calci- um inhibitors, encourages gener- ation of nucleation sites in the water that encourage scale to form but the resulting crystals are smaller so they stay in the water rather than adhering to the metal sides and thereby causing scale build-up.
The use of water softeners and scale inhibitors can go a long way towards alleviating the problem but with stored hot water sys- tems, apart from calcium water softeners if, after passing through the conditioner, hot water is sub- sequently stored in a cylinder then after 24 hours the process is reversed and scale begins to build up again. On top of this, any seri- ous turbulence can affect per- formance and scale up the heat exchanger – ie where there are tight bends in the system. Continuous flow water systems are the easiest system to keep scale free. When quoting for big installations, for example, multi- ple showers and numerous wash hand basins – continuous flow
systems save 30-35 per cent on install and around the same on gas costs. And there is no costly messing around with salt-based conditioners. Even where a ‘turnkey pack’ system such as the Rinnai Infinity Plus Storage is fitted and a booster tank added the water is unlikely to be held for 24 hours. These sys- tems are commonly used in hotels, for example, to deal with peak demand times and because these recover in minutes, scale is never likely to be a problem. To be sure limescale is never a problem, Rinnai heaters also incorporate a scale warning device that continually monitors the appliances for limescale deposits around the heat exchanger. Once lime scale build up has being identified, a message is sent to the built-in interface panel on the front of the appli- ance to alert the end user that it is time to call a Rinnai service agent to perform a lime scale flush. For a ‘belt and braces’ solution a continuous flow system, com-
bined with zinc treatment means end users can virtually say good- bye to scaling. The process gives up zinc ions that stay in the flow for a longer conditioning cycle. For the sake of a small cash out- lay, (as little as £200 depending on diameter of pipe), a zinc con- ditioner is a useful safeguard and one that will give end users addi- tional peace of mind. Unlike calci- um water softeners, zinc treat- ments only need attention every 2-3 years, which could be simply built into the maintenance con- tract, thereby keeping costs down. // The author is a sales consultant for Rinnai //
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