Heating efficiency for today
Multi-boiler installations in cascade offer particular advantages where demand can vary widely throughout the year. This installation makes use of Buderus GB162 boilers.
Richard Evans explains why high-efficiency and condensing boilers are still one of the most popular ways to meet the energy requirements for modern heating systems.In recent months we have seen the cost of oil rise again, nuclear power come back on the agenda, increased reports of pressure on future gas supplies and further Government promises to improve energy efficiency in the home and workplace. It is not surprising, therefore, that heating-industry headlines concentrate on renewables, biomass, wind power, ground-source heat pumps and the like. These technologies will clearly shape the future of our industry and, in some cases, will replace conventional boilers in new build projects altogether. Upgrading
However, there is a job to be done right now, and considerable energy savings can be achieved, in line with Government objectives, by upgrading old and inefficient commercial heating systems with state-of-the-art condensing boilers and controls. There is a wide range of renewable solutions available, but the latest industry figures show that the number of actual renewable installations, particularly in the commercial sector, remains a surprisingly small percentage of the overall heating market. The demand is clearly there, but when you consider the profile of these technologies in relation to the tried-and-tested condensing boiler, we have to ask why the switch-over is not happening more quickly. In contrast, the demand for condensing boilers for both new installations and replacements continues apace — and for good environmental reasons too. Most current demand for heating systems is fulfilled by condensing boilers — particularly in the commercial and industrial sectors. For businesses and institutions in both the private and public sectors it is important to maximise energy efficiency to reduce fuel bills and to reduce environmental impact. Today’s modern boilers are very efficient indeed, All boilers in the Buderus commercial range, for example, including cast-iron models, offer efficiencies over and above the 84% efficiency threshold stated in Part L2 of the Building Regulations. Savings on fuel bills can be well over 25% when condensing heating systems fitted with advanced controls are compared with the 20 to 30 year old commercial installations which they are normally replacing. There is no reason why boilers should be considered as a second choice to the more fashionable renewables. In fact, a combination of the two systems is likely to offer the best solution in many cases. Boilers are a highly cost-efficient solution in their own right and will continue to be so for many years, certainly throughout their typical life expectancy of 15 to 20 years. It is environmentally advantageous to replace old, inefficient boilers with modern versions as soon as possible, and this is still the first step to a truly efficient heating system and reduced carbon emissions. The ultimate aim of achieving a zero-carbon installation should not be used as an excuse for keeping inefficient heating systems in operation for longer than they should be. So how does today’s heating system designer achieve the best environmental performance from today’s breed of traditional-style boilers. The key is, of course to minimise emissions. which means maximising energy efficiency of the whole system — including the boilers themselves and the control systems. The less the fuel used, the lower the emissions. Wherever possible this means choosing a condensing boiler as the most energy-efficient solution. There is a huge range of condensing boilers covering a wide variety of types, including wall hung and floor standing, cascades, sectional of cast iron with stainless steel heat exchanger, condensing stainless steel and condensing premix boilers. Selecting the most suitable boiler depends on the specifics of each installation. Considerations will include access to the heating room and the space available in it, maximum system pressure, noise levels, weight, integration into an existing large-volume heating system, a complete new installation, as well as the all important efficiency of performance and minimal emissions.
An example of a condensing boiler that can be installed in existing heating systems is the Buderus GB312, with outputs of 90 to 280 kW and modulating down to 30% of full output.
It can be a complex decision, and Buderus recommends consultation with technical experts to assist in making this decision for major heating projects. Careful, considered selection is necessary to achieve the optimum efficiency. The whole system should be reviewed to maximise efficiency. Factors to be considered include insulation levels, pump sizing, hydraulic design and, importantly, the selection of controls systems with weather-compensation, optimising and zone controls. The development of cascade multi-boiler installations provides a highly efficient and economical alternative to the larger single boilers and has advantages especially where demand levels can vary widely throughout the year. The Buderus GB162 range, for example, offers cascades of up to eight boilers which can be fitted in line or back-to-back. Four such boilers occupy just one square metre of floor area and have an output of 400 kW. They can be automatically controlled to modulate to maximise energy efficiency. Whatever the heating requirement, there is a boiler available for a completely energy-efficient solution. The sooner a high-efficiency boiler system is installed to replace an existing system, the sooner the savings will be seen and emissions reduced. The latest condensing and high-efficiency boilers are the present-day answer to energy-efficient heating and hot-water systems. Richard Evans is director for commercial boilers with Buderus in the UK.