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Recognising & Eliminating Limescale in Commercial Hot Water Systems

Recognising and eliminating limescale In large commercial-scale hot water systems is a critical maintenance activity for many organisations. Limescale deposits can wreak havoc on efficiency, longevity, and overall performance. In this blog, we continue to explore resilience in commercial water heating and look at the latest developments securing business continuity in hard water areas…

The severity of limescale formation depends heavily on the water hardness in a particular region. Geographically, areas with limestone bedrock tend to have harder water. Approximately 65% of the UK mains water is currently classed as ‘hard’ due to the presence of calcium. Hard water with its high concentration of dissolved minerals, primarily calcium and magnesium bicarbonates, is one of the primary requirements for the development of limescale. The other, and the catalyst for the process of limescale formation, is the application of high-intensity heat.

As water in a commercial hot water system heats up, the solubility of calcium and magnesium bicarbonates decreases. This decrease is not uniform; it accelerates significantly at higher temperatures, triggering a chemical reaction which causes the now less soluble bicarbonates to precipitate out of solution and form solid calcium carbonate (CaCO₃) – the main constituent of limescale. Studies indicate that limescale starts precipitating around 35-40°C (95-104°F) and worsens progressively as the temperature climbs. This explains why heating elements, with their concentrated heat, are prime targets for limescale build-up. The recent shift in popularity for electric systems has seen issues with limescale notably increase where electric heating elements, i.e., immersions, with high-intensity heat generation are used as primary heating systems in direct contact with main flowing water.

The design and flow dynamics within a commercial hot water system can also influence limescale formation. Areas with low water flow or stagnant zones are particularly susceptible. For instance, in water heaters where mains water is constantly heated, the potential for scale buildup is high due to the continuous precipitation of minerals. Dead legs, sections of pipe with minimal flow, are another prime location for limescale accumulation.

 

The Damaging Effects of Limescale Buildup

Allowing the buildup of limescale in commercial hot water systems creates a series of problems:

Reduced Heat Transfer: Limescale acts as an insulator, hindering the transfer of heat from the heating element to the water. This translates to increased energy consumption to maintain desired water temperatures, driving up operational costs.

Inefficient System Performance: As limescale accumulates on heating elements and heat exchangers, the system’s ability to heat water efficiently diminishes. This can lead to longer heating times, decreased hot water availability, and potential disruptions in hot water usage.

Increased Risk of Component Failure: Heavy limescale buildup can restrict water flow within pipes and clog valves. In extreme cases, it can even cause components to malfunction or seize up completely, leading to costly repairs or replacements.

Corrosion Concerns: While a thin layer of limescale can act as a protective barrier against corrosion, uneven or excessive buildup can disrupt this protection. This can expose underlying metal components to corrosion, leading to premature equipment failure.

A New Strategy For Eliminating Limescale

Popular strategies for addressing limescale deposition in commercial hot water systems begin with optimised system design which minimises areas of low flow and stagnation zones and regular system maintenance, including flushing and cleaning, to help prevent excessive scale accumulation. The problem is that in hard water conditions, such as those seen in London and the Southeast of England, direct electrical systems can begin to scale heavily in a matter of weeks not months demanding a more thorough yet cost-effective response.

Some will try an approach which lowers the operating temperature of the water in the system to reduce limescale formation. This is counterproductive for commercial applications which increasingly demand high-efficiency, high-temperature water heating to meet safety and operational requirements.  As we have discussed, the overall system temperature may not be the issue anyway, but rather the presence of high-intensity heating surfaces which initiates the precipitation of limescale.  Others have adopted water softening through a process of ion exchange or chemical dosing. In our experience water softening systems rarely deliver on their claims. Chemical dosing whereby phosphate-based treatments are commonly used to modify the water chemistry and inhibit the precipitation of minerals can really help, but they are prone to being forgotten or overlooked over time. The problem is these approaches require consistent monitoring and re-application. When operational costs begin to climb, this simple maintenance is one of the first things to be pulled, usually with disastrous effects. 

With the increasing demand for low-carbon all-electric hot water applications, the threat from limescale has increased considerably. As Adveco develops its own unique product and applications to meet the change in desired energy source, and the physical transition of many buildings from legacy gas-based systems to electrical water heating addressing this familiar threat has become paramount. Reacting to this increasingly common threat to the efficiency and longevity of commercial hot water systems and therefore the successful roll-out of low-carbon net zero systems, Adveco has taken a different approach to not just reducing but virtually eliminating the creation of limescale, even in the hardest water areas.

Eliminating limescale creation with FUSION technology 

Key to Adveco’s net zero portfolio of products is the FUSION system of all-electric water heaters which combine a variety of well-understood technologies in pre-sized packaged variants. Built around a tough, ant-corrosive stainless steel indirect cylinder that acts as the system thermal store, FUSION uses an electric boiler to provide primary top-up heat. This is then offset by an air source heat pump to lower energy demands and cut carbon emissions. Additionally, water heating can be backed up with an immersion for short-term emergency redundancy.

The key to addressing scale build-up is the combination of electric boiler and indirect cylinder which works with a finite amount of water. This, along with specially developed controls which finely balance the hot water production limits the actions that generate limescale to the point where we can show virtual elimination of the issue which remains prevalent in other systems at the same location.

Discover how Adveco demonstrated virtually eliminating limescale from a restaurant’s hot water to ensure business-critical daily operation with a development application that would become FUSION.

Also, read Adveco’s handbook on eliminating limescale in electric water heating systems