Ecient producon of bulk hot water is vital for many commercial

buildings but with a variety of opons available, what should specifiers look out for? Mark Ferris, Specificaon Manager at ELCO Heang Soluons discusses the opons.

healthcare facilities and stately homes, day-to-day running of a building is wholly reliant on effective hot water delivery. Not so long ago, only a handful of water heaters were on the market, whereas today, there is a wealth of products available for a commercial project. So, where should specifiers begin?


Well, the first important note relates to atmospheric water heaters and the Energy Related Products Directive (ErP). From September 2018, units of this type will need to meet the compulsory efficiency requirements. Therefore, it stands to reason that some products on the market today will not comply after the autumn deadline.

The second consideration is the level of domestic hot water (DHW) needed for the project, which can usually be split into the categories of continuous demand, intermittent peaks and short heavy peaks. For continuous and intermittent peaks, which often occur in sports clubs and leisure centres, a direct gas-fired condensing instantaneous water generator is a tried and tested method. These provide extremely high volumes of DHW as well as consistently high efficiencies, thanks to their integral condensing boiler technology. Consequently, they can satisfy the most demanding applications, while offering high gross seasonal efficiencies, allowing units to complete their task effectively all year round.

Scale fouling

Despite their impressive performance, the risk of scale fouling in direct-type units is a potential issue that must always be considered. In some cases, even a thin layer of scale can lead to problems within a heat exchanger. So, it is essential for specifiers to factor in two things. Firstly, the flow rate must be carefully regulated. And,

ot water services are crucial in many commercial

buildings. Indeed, from hotels and leisure centres, to

secondly, it is essential to specify a water heater that has been manufactured to the highest standards, accommodating an overall design and specialised internal componentry suitable for the task. Take the new TRIGON XL WH from ELCO as an example; this unit has been specifically designed for the water heating market and, consequently, is suitable for commercial applications that require large quantities of hot water. The main reasons for its suitability rest in its design, which features an advanced premix-burner system for reliable performance, a water- cooled combustion chamber for the highest possible thermal conductivity, and optimised combustion zones for low emissions. These attributes, combined with a high grade stainless steel heat exchanger, result in unbeatable hot water performance – providing a continuous supply of hot water at an efficient recovery rate of up to 9,257 litres per hour (50K delta T). An alternative technology to contemplate is an indirect gas-fired condensing unit. This provides complete hydraulic separation between the primary heat exchanger and the tap water, which greatly reduces the potential problem of scale-fouling.

Peak usage

Fully condensing indirect units with built in storage can be a useful option, as they provide near instantaneously heated water, plus volume hot water delivery for peak usage. Incorporating the storage vessel within the unit also reduces long pipe runs, which are associated with a separate boiler and indirect cylinder. This design keeps heat losses to a minimum.

Another benefit of fully condensing indirect units with built in storage is the principle of loading the storage vessel from the top down with a very wide temperature rise. This approach contributes to near fully instantaneous performance and optimises the efficiency, as the feed water to the heat generator is picked from the

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EFFECTIVE HOT WATER DELIVERY Taking direction on hot water production

lowest point in the storage vessel, where the water is always the coolest at any given moment. Such a setup ensures units work in condensing mode for the vast majority of their operating cycles.

Whichever technology best suits the application, the positioning of a water heater is an important aspect. It should, generally, be installed close to point of use, as this reduces the energy usage associated when supplying water over a long pipe run. It also minimises distribution heat losses and limits the length of ‘deadlegs’ in the system, which will ultimately help compliance with ‘The Control of Legionella Bacteria in Water Systems’ outlined by the Health and Safety Executive (HSE). This states that pipework should be adequately designed to reach all outlets at 50ºC within one minute of turning on the tap*.

Footprint and weight

There are also a number of practical considerations when specifying larger gas-fired water heaters, including the footprint and weight. This is often heavily related to the design of the unit itself, so it is worth bearing in mind the overall design of a water heater early on during specification. Manufacturers are continuously developing designs to make installation and servicing simpler. An example of this is a modular design, which allows a unit to be disassembled into component parts, then reassembled when in situ. This can make installation far easier, especially in hard-to-access plant rooms. A final thought on the specification of gas-fired water heating units is their overall aesthetics. This might sound like an unnecessary deliberation, but more and more clients appreciate plant rooms that reflect the clean and efficient performance of the system, especially in prestigious buildings. With this in mind, some manufacturers have developed models that complement the aesthetics of other heating equipment.

Of course, there is also a practical element to using models from the same manufacturer, such as aligning

uTrigon XL WH from ELCO Heang Soluons.

maintenance schedules and the possibility of sharing some first line spares. Furthermore, units may be able to share flue systems if they have the same operating characteristics as their combustion systems. So, rather than having to incorporate two outlets, they could utilise the same flues as the heating boilers, facilitating installation and reducing overall costs.

There will always be a need to deliver powerful and effective DHW in commercial applications, which means dedicated water generators will always be in demand. However, with several options to choose from, it’s important for specifiers and building services engineers to carefully consider all of the pros and cons associated with each technology. Calling upon a manufacturer for advice is often a useful approach, where guidance on the best method can be provided early on in a project. Once a detailed evaluation of all the options has been completed, there is every reason for DHW to be delivered effectively on a project, keeping energy usage to a minimum – while maintaining a reliable system. Sources: priced/l8.pdf

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