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Setting the agenda for boiler control



While most large buildings now have programmable and intelligent controls system installed, boiler management needs more focus



The publication of two White Papers on energy in the space of three years shows how seriously the government regards the subject. With long term concerns about security of supply and about climate change, it is seeking ways of reducing energy consumption and emissions. The 2006 White Paper identified a number of options.

The first priority set out in both White Papers is to save energy and to use it more efficiently. This reduces overall demand, cuts emissions and saves the consumer money, which can be usefully redirected into other avenues such as front-line services. Initiatives like the Carbon Reduction Commitment, the introduction of energy certification and the roll-out of smart metering are all aimed at moving the UK towards a low-carbon future.

Although new buildings are very well-insulated nowadays, space heating and hot water still account for the major part of the energy demand for most organisations, especially those with older premises. Most heating plant has some form of control in the form of optimisers, sequencing and zone compensation, and many are incorporated into the building management system. Yet the philosophy of boiler management has changed little over the past half century.

The boiler
Nearly all commercial boilers will have their supply temperature setpoint at a static 80°C. The boiler attempts to reach these setpoints by reheating water returning to it after the heating demand of all independently controlled zones in the building have been satisfied. Typically in spring and autumn, when heating demand is lower, most systems mix flow and return water to try to balance the boiler’s supply temperatures with building demand. This process wastes a considerable amount of heat.

You do not run a motor at full revs when you only have a part load - not any more anyway, because you install a variable speed drive (VSD) to adjust the engine work to the load. This is now mandatory for variable air volume air conditioning and for a host of other motorised applications in buildings. The change took some time to be accepted but now it is the norm.

If you would not run a motor at full throttle on part load, why run the boiler that way? Adjusting the boiler output temperature would surely be a simpler and more efficient way of working. The question is: can this be made to work in practice, rather than just in theory? Well, the European Commission thought it sufficiently interesting to fund research and the UK building consultancy BRE was the principal research body involved. At the end of the project, they concluded that with the boiler controller developed (now known as the ‘Fuelstretcher’) , “up to 30 per cent of energy saving can be obtained in systems with uncontrolled terminals”. And savings of up to 10 per cent were possible where the controller was interfaced with a BMS.

The technology is now being made on a commercial scale and is in place across the UK. It can be used on its own to regulate the boiler output temperature or interfaced with a BMS. The technology senses the aggregated return temperatures from all building zones; it dynamically integrates the signal and adjusts the boiler setpoint (supply) accordingly.

Swansea Civic Centre (pictured left) was fitted with Fuelstretcher technology and its performance independently monitored in early 2005. The building’s internal environment is controlled by a Building Management System. The technical analysis of the unit’s performance, prepared for the Consortium of Local Authorities Wales (CLAW) Energy Managers Group, “identified a 21 per cent saving in gas consumption when the building was under the control of the Fuelstretcher”.

With or without BMS
Fuelstretcher can be just as effective in buildings without a full BMS. The London Borough of Sutton installed the unit in an education administration building dating from the first half of the last century. Not only was internal comfort improved but the unit achieved weather-corrected savings in gas consumption of more than 20 per cent.

In Northern Ireland, the technology is proving particularly popular in the education sector where it has been fitted to 95 schools by the Province’s leading Building Management Systems Integrator. Many schools have a BMS installed. The technology is approved by The Energy Saving Trust for grant funding in this part of the UK and school energy bills have been considerably reduced through its application

Technology has a major part to play in delivering the energy and carbon savings needed to meet the government’s policy goals. Boilers are among the largest consumers of energy in any organisation, so it is vital that they are used as efficiently as possible. Dynamic, automatic setpoint adjustment is a simple and very effective way of doing this. Condensing boiler efficiency is gaining from resulting lower system temperatures.

For more information
Peter Jennings is Chief Executive of Fuelstretcher Ltd. For more information visit: www.fuelstretcher.co.uk or telephone: 01752 764423