BSEE BOILERS & HOT WATER
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THE RIGHT BOILER FOR THE RIGHT PROJECT Overcoming the challenges of boiler upgrades
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Ian Bradley, Managing Director at ELCO Heating Solutions, discusses the advances in commercial boiler design, from a practical and operational perspective, and how they can make retrofitting simpler.
n today’s new build commercial property market, it’s rare to come across a plant room that hasn’t been meticulously designed, especially in buildings that are purpose-built and have utilised BIM from the outset.
Boasting elegant cascade arrangements of boilers, perhaps a CHP in the corner, complemented by banks of controls feeding back to a building management system – a modern plant room and its contents have all been designed to ensure heating and hot water is delivered at optimum output and efficiency. Compare this to a commercial boiler plant room built 20 years ago – which has been adapted over the years to suit changing requirements of the building and its inhabitants – and it is likely to be very different place. The original boilers are likely to still be rooted in place, linked to the bare minimum of controls, all left to deliver heating and hot water without any (recognisable) need for change. Of course, this is acceptable until the running costs of the system become prohibitive, or the savings from switching to condensing units makes financial sense. It is at this stage when a few practical challenges are presented to system designers.
Access
The first consideration should be physical access to the plant room itself. Very often, as older commercial buildings age and evolve over the years, access can become difficult, with narrow corridors and staircases, or even impractical lifts. This is where a new boiler with a modular
construction can be a huge benefit in retrofit situations, as it can be disassembled into its component parts on site, taken to the plant room and then reassembled in situ.
uTrigon XL can be broken down and reconstructed in less than half a day, making it perfect for buildings with limited access.
This might sound like a complex task, but a boiler such as the TRIGON XL from ELCO Heating Solutions has been specifically designed with this purpose in mind and can be broken down and reconstructed in less than half a day. Alternatively, specifying a commercial boiler which is able to fit through standard door widths (760mm) is advisable, as this makes it simpler and quicker to move the units on site.
The second important aspect of any refurbishment is the floor space. Original boilers in an old commercial property are usually ‘standard type’ appliances butted up next to each other. Despite being relatively inefficient, these units are still able to provide a high system output from a small floor area. However, when replacing them with condensing versions, additional side access and clearance is needed for maintenance purposes.
For this reason, a handful of leading boiler manufacturers have invested heavily in developing floor standing condensing models that can produce extremely high outputs from a small footprint, while still allowing practical access to key components within the boiler. Indeed, it is now possible to configure floor standing condensing units far closer together than previously possible. This has always been an issue over the years, so it’s recommended checking the options at the specification stage.
System design
Once these first two practical considerations have been addressed in a retrofit scenario, it leaves the important element of system design conditions to be faced. Typically, condensing boilers are designed to operate with a delta T of 20°C, whereas the standard type commonly installed in the UK traditionally operate at an 11°C, with flow and return temperatures of 82°C/71°C. It is easy to innocently overlook differences between the existing system and the requirements expected from a replacement boiler. However, taking these factors into account at the planning stage can help eliminate potential problems, and one option available to system designers is a low loss header. This provides the ‘convertor element’ and allows traditional load circuit design conditions to be accommodated. The low loss header is not only employed as the interface between the boilers and the system, but it also acts as a blending device. Of course, it must be configured to handle the greater of the two mass flow rates, i.e. the secondary or load side, and the new boilers should be able to operate at a flow temperature of 91°C. However, if the heat generator taking care of the consumer side is well matched and mass flow rates are correct, then the rest should be automatic.
Internal components
So far, the practical elements of boiler design have been considered. But what about the internal components of a new condensing appliance; how are they designed to cope with the challenges of a commercial heating system and do they differ from boiler to boiler? In truth, there is one key component that needs to be considered ahead of any other: the heat exchanger material. Generally, this material is either stainless steel or aluminium. At ELCO,
16 BUILDING SERVICES & ENVIRONMENTAL ENGINEER JULY 2017
stainless steel is the preferred material of choice because its properties allow a heat exchanger to maintain published performance figures for its entire operating lifecycle.
Unfortunately, this cannot be said for all metals.
Aluminium, for example, has been shown to significantly drop in efficiency over its lifetime due to its gradual corrosion. Combined with the unavoidable build-up of ‘sludge’ from aluminium oxides, heat exchangers of this type are often unable to cope with the tough requirements of a commercial heating environment.
Corrosion
Stainless steel, on the other hand, has is an inherent resistance to corrosion, which is especially important when it is subjected to the demanding conditions inside a boiler’s hydraulic system.
There are thousands of non- condensing commercial boilers still in operation throughout the UK, which will need replacing over the next decade. Undoubtedly, there will be individual challenges during an upgrade, whether it is the access, floor area or operating conditions. However, as outlined, if all these aspects are addressed/considered early in the retrofit process, there is no reason why a boiler installation should be a complex task. Indeed, the process should be a simple one and deliver significant improvements in efficiency and running costs. It’s purely a matter of identifying the practical considerations early on and then choosing the right boiler for the project.
www.elco.co.uk ‘ Specifying a commercial boiler which is able
to fit through standard door widths (760mm) is advisable, as this makes it simpler and quicker to move the units on site.
’ VISIT OUR WEBSITE:
www.bsee.co.uk
uElco’s TrigonX – a new boiler with a modular construction – can be a huge benefit in retrofit situations.
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