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BOILERS & HOT WATER BSEE


CENTRALISATION VS DECENTRALISATION Let’s look at all the pros and cons


When deciding where to install water heaters and associated distribuon systems, is it beer to have a small number of localised systems that are closer to their points of use, or a larger, centralised setup? Dave Ridgway, Applicaons Manager at Andrews Water Heaters, discusses how modern technology might finally be seling this long running debate.


of solution appeared to gradually fall out of favour, particularly from the mid-1980s, as decentralised systems promised to deliver better results in terms of economic and energy efficiency as well as legislative compliance. Over the last decade, though, technology has advanced considerably and the solutions available for water heating today are now much improved compared to those in use 20 or 30 years ago. As a result, centralised heating systems are once again being considered for all types of commercial properties by owners and managers in both the public and private sectors. Commercial businesses, such as hotels and office blocks, are under pressure to ensure compliance with a range of new regulations. The built environment has been identified by government as a threat to the UK meeting its carbon reduction targets for 2020 and 2050 and estimates suggest that 18 per cent of commercial properties hold the lowest EPC ratings of F or G.


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With that in mind, we explore the pros and cons of a large centralised hot water system compared to a few localised systems close to their point of use.


System design


uA variety of factors will influence the design of the system and much will depend on the type of building and its water usage requirements.


A number of different factors will influence the decision on how the system should be designed and much will depend on the type of building and its water usage requirements. One of the main considerations is the size of the plant room. In period buildings, the basement under the building or ground level is often used to accommodate plant and equipment. Whereas, in modern, multi-storey buildings, underground basements are not always available due to the method of construction so plant tends to be sited on the upper floors, or even on the rooftop.


entralised plant rooms for heating and hot water systems have been around for decades. However, this type


The availability of space to install and maintain a separate water heating system is crucial and buildings with footprint constraints will need to explore other options than a large centralised water heater solution. The advantage of decentralised systems is that they are modular in nature, meaning that that they work well in premises that need to adapt. For example, when Potters Leisure Resort near Great Yarmouth added a newly built 84 bedroom hotel to their holiday accommodation options, Andrews Water Heaters’ products were specified to provide the hot water services for the en suite shower and bathroom facilities.


Being independent gas-fired units, they are very economical to run and are particularly well-suited to being installed in a decentralised system, operating in zones with the flexibility to add more units into the system as the resort has grown. Over the years this has prevented system redesign and replacement, which could otherwise have been very costly.


Energy eciency


Another major consideration when specifying a water heater is energy efficiency, particularly in light of the recent raft of regulations impacting the sector. EU energy labelling and Ecodesign measures, for example, have sought to reduce consumption by setting requirements on energy efficiency, nitrogen oxide emission levels, volume for storage water heaters and heat losses. In the past, the criticism of large centralised hot water systems was that energy was wasted when there’s little demand for hot water because heat is being lost from long pipe runs. The argument was that installing individual heaters where the hot water is actually needed means that the water system can be designed with shorter pipes and less heat wastage. However, advancements in building fabric and insulation in modern buildings have meant that energy performance has rapidly improved along with improved pipe insulation materials. Optimum design of building fabric can now minimise potential heating and cooling requirements, which may lead to the downsizing of heating and cooling systems. With better insulation, building managers can opt for a centralised plant with a bigger kilowatt output.


Servicing and maintenance


One of the main arguments in favour of a centralised system revolves around the issue of maintenance. That is because a decentralised solution can be complex to manage with separate gas connections or runs required for each heater.


A building with, say, 20 water heater appliances spread over eight floors,


would cost significantly more to service than a building with one large water heater. Furthermore, if there are different organisations in the building, a common challenge can be gaining access to the units in the first place. New technology has also become available in recent years that makes the maintenance of a centralised system even easier. Heat interface units (HIU) provide localised control and metering in a self-contained package, allowing simple integration into a larger heating and hot water system.


Acting as a bridge between the central boiler and the heating and hot water systems of different areas in a building, HIUs require only a hot heating riser connected and no building-wide gas or flue network. With no individual gas boilers, there are reduced risks associated with gas distribution pipework, saving on installation costs and reducing the need for individual flue terminals (with associated plumbing). The annual gas safety inspection is typically restricted to the plant room, and a reduction in operating costs owing to reduced boiler service.


Ultimately, the perfect system will depend on the type of building and the needs of its occupants. As we’ve discussed, the design of a hot water system depends on factors such as plant room footprint, but developments in modern building standards means that some of the historic concerns around the energy efficiency of centralised systems are no longer relevant.


Although some buildings will require a decentralised approach due to their physical layout and the needs of occupants, with new technology becoming available that helps to significantly streamline the maintenance process, centralisation of hot water systems appears to be back in vogue.


uNew technology is helping to significantly streamline the maintenance process, with centralisaon of hot water systems appearing to be back in vogue.


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Technology has


advanced considerably and the soluons available for water heang today are now much improved compared to those in use 20 or 30 years ago. As a result, centralised heang systems are once again being considered for all types of commercial properes.


’ www.andrewswaterheaters.co.uk VISIT OUR WEBSITE: www.bsee.co.uk BUILDING SERVICES & ENVIRONMENTAL ENGINEER JULY 2018 19


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