Efficiency is in the water

The latest commercial boilers offer extremely high levels of performance and efficiency, but they should not be thought of as stand-alone solutions. Boilers function in systems that must be deemed healthy in a whole sense; and essential to this health is the lifeblood that supports it – water. Incorrectly or insufficiently treated water can lead to many undesirable consequences, such as boilers, pipework and radiators blocked with contaminants in the form of iron oxides, sludge and/or limescale. So, what are the key considerations for cleaning and protecting heating systems? Ian Barnes of Sentinel Commercial provides some key pointers.

The importance of water treatment should never be underestimated. A heating system’s operational efficiency can only be maximised if system water is clean and free from limescale, iron oxides and sludge. Few untreated commercial facilities are immune, with these problems applying to small and large heating systems alike, and all types of heater: radiator-based, under-floor and renewable energy (solar thermal, ground source/air source, heat pumps). Furthermore, failures or subsequent component (or entire system) replacements due to the accumulation of deposits within pipes, valves and heating elements can be avoided by ensuring that the circulating water is high in quality. Ultimately, water treatment is more an essential choice than an optional extra.

Water hardness is the chief culprit for direct fired water heaters, a factor that can be determined by its calcium bicarbonate content. This is expressed typically in either mg/l or parts per million (ppm). Water with a concentration in excess of 300ppm is considered very hard. Dropping down the scale, water with a concentration between 200-300ppm calcium bicarbonate is considered hard, and moderately hard water is 100-200ppm.

The unfortunate geological fact is that approximately 60% of the UK is subject to hard water conditions. To make matters worse, heating hard water increases the chances and rate of limescale deposition. As a result, the worst affected system components are often the heating elements.

The way around the problems presented by hard water is to either relocate to a soft water area (not commercially viable or practical for most) or to use water that has been treated correctly. Deploying appropriate and effective water treatment will bypass any potential for limescale accumulation, especially in ‘once-through’ water heaters, and even closed heating systems that have undetected water losses.

Water treatment

But the benefits don’t end there. Water treatment makes sense for any commercial organisation looking to boost their environmental credentials. Improved heating system efficiency will both reduce emissions and energy bills, and possibly even the company’s CRC commitment. The upshot is that the potential advantages of water treatment should be considered very seriously, both from an environmental and financial perspective. British Water reports that a layer of limescale just 1.6mm thick can add to a system’s energy demands by as much as 12%. Considering that energy is one of the largest overheads any business can face, this is a significant figure.

There are more financial incentives to be had long term, particularly in respect to life cycle costing. For instance, in the absence of scale or other oxide-based deposits, heating appliances and pipe work will need replacement far less frequently. Installing a new heating system not only commands considerable capital cost, but is disruptive and could possibly even require the closure of certain business areas/operations while the work is taking place. A lack of business continuity can be extremely damaging to customer relations, reputation and the bottom line. Unfortunately such problems are heightened in many commercial applications where the narrow waterways of common plate heat exchangers are especially liable to scale formation and deposit accumulation.

So, what are the principal solutions available? Well, perhaps unsurprisingly there are numerous options for the treatment of water in commercial facilities. However, system operators and specifiers should beware that some technologies make claims that have yet to demonstrate any credible validation. The tip here is to do some homework – always chose OEM approved products and be sure to consult experts before deciding on a particular product.

Range of solutions

Current water treatment solutions extend from liquid inhibitors introduced to the heating system water, to conditioning technologies that function by deploying a zinc anode and copper cathode to inhibit the formation of limescale by manipulating calcium carbonate precipitation and transforming it into a non-adherent crystalline form.

By way of a general guide, if selecting a liquid inhibitor for a closed or vented heating system, for example, it makes sense to choose one that features more than a single type of corrosion inhibitor. Doing so will ensure that protection is maximised for all different metal types. In addition, for optimum results, it is vital to match the chosen solution to the system needing protection, so that its precise requirements can be met. Many make the mistake of selecting a product to suit the existing hardware, whatever its condition and environs. Take the example of a Victorian town hall. The older pipework within such a building will demand a somewhat gentler approach to that of a two year old office block. Installing a product that is too aggressive for older pipes could compromise their integrity and introduce problems and costs that weren’t there before.

Moving to the selection of devices that encourage precipitating calcium carbonate crystals to form as soft non-adherent Aragonite rather than hard deposit-forming Calcite – these become a preferred choice when water conditioning is required for a direct fired water heater (where it’s critical to reduce long term maintenance costs), or if there’s a need to treat both hot and cold supplies.

Moreover, because the treatment does not decay on standing or agitation, units of this type can be fitted to the rising main, before the water storage tanks and booster sets. The advantage here is that the capital expenditure is less in comparison with corresponding installations on larger distribution pipes. It is also worth noting that no separate drinking water supply is required providing the unit of choice is WRAS approved – KalGUARD+ is an excellent example.

Maintenance for zinc anode based physical devices is minimal, with filter flushing recommended twice a year. If required, some manufacturers will offer a technical field service contract to ensure that the unit operates at optimum efficiency. Visits from a service engineer normally include a field diagnostic check, filter flushing, water testing to assess any changes, water use evaluation and, if necessary, the adjustment of settings. Such maintenance requirements are in stark contrast with traditional ion exchange water softeners, where daily top ups of costly salt are the norm.

Initial clean

Naturally, if the system has been operating without any form of protection whatsoever, then it’s advisable to perform a clean prior to introducing a water treatment solution. Failure to do so can reduce the positive effects because debris, of one type of another, will always be present. For instance, corrosion generates a black iron oxide sludge that transfers through pipework affecting pipes, pumps, seals, heat exchangers and diverter valves. In basic terms, there is little point in adopting any form of corrosion or limescale protection unless the system itself is initially clean because the maximum energy efficiency benefits will never be achieved.

Due to the presence of numerous water treatment options, along with the fact that it is vit
al to get the correct one for each commercial application, choosing a solution can be something of a black hole for the unenlightened. But all is not lost: thanks to the support made available by many manufacturers, it needn’t be difficult. Most offer a technical department able to deliver advice and training wherever required. With this in mind, heating engineers and building services managers can always be sure of selecting the best product for the task in hand.