How effective control equals effective heating

Published:  02 February, 2012

BMS, controls, Buderus, boilers
Controlling costs — Pete Mills.

Is your new and efficient boiler installation as efficient as it should be? Not if it doesn’t have decent controls — argues Pete Mills.

As modern condensing-boiler technology continues to advance at speed, so too does that of the controls used to operate it. Whilst it could be argued that little attention is often paid to the controls used to regulate the way a building’s heating system operates, a sophisticated controls system can be key to ensuring that a boiler system can operate as efficiently as possible, which is then reflected through minimal energy costs and carbon emissions.

Under the present Building Regulations Part L, minimum control packages are required for new buildings in addition to only installing gas boilers with a minimum efficiency of 86%. All new installations must incorporate timing and temperature controls, which must be zone specific for buildings with floor areas over 150 m2. In addition, weather compensation controls are also required unless a constant set temperature is needed.

Further to these requirements, installations from 100 to 500 kW are also required to have optimal start/stop control with night set backup or frost protection, 2-stage firing facility for multiple boilers, measures to limit heat loss from non-firing modules and sequence control for multiple boilers. Boilers over 500 kW must also have fully modulating burner controls.

A sophisticated solution

Weather compensation in particular lends itself to condensing systems as it controls the boiler flow temperature based on the outside air temperature. This helps the boiler to condense for much of the year, which provides a good level of control over larger building areas. Popular across much of mainland Europe, weather-compensation controls offer quick payback for a relatively small initial investment. As is the issue with many of today’s sophisticated heating controls, however, the key to maximising its potential lies with educating the end user on how to use such a system to make the ultimate savings on offer.

One of the issues regularly encountered by facilities managers is the complexity of the control system and the interface between the controls provided by the boiler manufacturer and the existing building-management system (BMS). As a result, there is often some confusion over, for example, which controls take over the sequencing of a multi-boiler cascade system.

Multi-boiler cascade systems are generally used to cater for larger heating demands particularly where limited access is limited rules out the installation of larger-output single units. In a cascade arrangement, up to eight boilers, for example, can be connected to one another to achieve outputs up to 800 kW. Such an installation requires a device to comprehensively manage boiler sequencing to ensure that each boiler in the cascade shares the output required to meet the building’s heating demand.

BMS, controls, Buderus, boilers
Top; The key to maximising the potential of modern energy-efficient boilers lies with educating the end user on how to use more sophisticated controls. Bottom; A suitable control system can significantly improve the efficiency of a heating system serviced by boilers.

Buderus’s experience of developing multi-boiler systems and associated controls across the Continent means that a comprehensive range of modular control options is available to suit the requirements of each system. It is important to appreciate that a building’s heating represents just one of the functions controlled by a BMS programme, so compatible, manufacturer-supplied heating controls should be able to manage the boiler system more effectively and at a much lower cost to the end-user than a generic control infrastructure.

Amongst many smaller to mid-sized commercial buildings, we see examples of where old and inefficient boilers have been replaced rapidly, but with little thought given to how the new system will operate throughout its expected lifetime. Simple on/off controls remain fairly common; however, it is important for end-users to realise how simple it can be to take advantage of the full potential of their heating system simply by investing in a more thorough controls system. Avoiding this issue and saving the cost associated with a modern controls package may save money in the first instance, but over the longer term, a lack of optimisation of the system will undoubtedly cost more.

Future-proofing

With the benefits of solar thermal collectors and the wider portfolio of renewable technologies available in the UK increasing because of rising energy costs, which are beginning to discourage many organisations from a wholesale reliance on fossil fuels, future-proofing a heating system is key to maximising savings. Whilst the stakeholder may not see renewable energy as a worthwhile investment at present, this may change over time, particularly as the Renewable Heat Incentive (RHI) and Carbon Reduction Commitment (CRC) grow in stature. As a result, it is always wise to ensure that the current heating system and its associated controls package can be upgraded to accommodate renewable technology at a later date.

The Buderus 4000 series of controls is an example of a package which is capable of optimising and future-proofing a heating system without a complicated or costly installation process. Such ‘off-the-shelf’ packages can often work with a range of plug-in control modules to match individual system requirements without the need for an expensive, bespoke solution to be commissioned.

Whilst the ultimate aim of a chosen heating-controls package is to deliver cost-effective answers to the questions often posed by the control of energy use, a well matched controls system can also deliver significant cost and emissions savings. These factors are given an increasing focus in the wider context of rising fuel costs and stringent environmental regulations, which are expected to gather momentum over the months and years to come.

Pete Mills is commercial technical operations manager with Buderus.



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