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Saving energy through continuous commissioning
New valve and control technologies can make it easy to ‘continuously commission’ fan coil and chilled beam systems as building usage changes, thus maintaining post-occupancy efficiency. Martin Lowe, Technical Manager with Marflow Hydronics, explains
One of the major challenges to maintaining the efficiency of a building’s services is being able to adapt those services as the use of the building changes. In recent years this has become even more of a problem as churn has increased and many organisations have been rationalising their building usage, resulting in changes to building occupancy density. There has also been a marked increase in the amount of hot desking and other flexible working practices, so that occupancy can vary considerably.
Furthermore, many buildings have undergone refurbishment of their fabric to improve insulation levels and ‘leakiness’ so that less heat is lost to the outside.
In addition, there are strong imperatives to introduce low or zero carbon (LZC) technologies such as heat pumps and solar thermal, which potentially change the water flow temperatures the systems use so flow rates have to be adjusted to compensate.
In parallel, the whole issue of post-occupancy efficiency has risen up the agenda, driven by initiatives such as the CRC Energy Efficiency Scheme, Energy Performance Certificates and Display Energy Certificates.
Fundamentally, if a building is going to be able to adapt to such changes, its services need a higher level of flexibility than has hitherto been the norm. Without that built-in flexibility any changes can prove to be very expensive and disruptive, so that very often the system is left to run inefficiently as this is the path of least resistance (and hassle).
One of the areas requiring particular attention is that of fan coils and chilled beams (hydronic systems) which have tended to be very disruptive and expensive to reconfigure. This historical inflexibility of hydronic system is in stark contrast to services such as lighting, where specifiers and building operators have recognised this issue and now make more extensive use of lighting management systems that enable ‘soft-wiring’ changes rather than extensive re-cabling.
Remote, continuous commissioning
In order to meet changing requirements and achieve ongoing flexibility and efficiency of hydronic systems we need a similar approach to that of lighting. And new valve and control technologies hold the key to creating a situation where fan coil systems and chilled beams can be re-commissioned from a remote PC. As a result, hydronic systems can become dynamic and able to respond to change without the disruption and expense associated with conventional re-commissioning exercises.
One of the key factors in moving towards this ‘continuous commissioning’ concept has been the development of addressable pressure independent two-port control valves (PICVs) that can be precisely adjusted through a building management system (BMS) or BACnet system.
As a result the valves are no longer ‘fixed’ and difficult to adjust. On the contrary, they can be rapidly adjusted to suit different circumstances with little or no disruption. And such solutions can be retrofitted to existing systems relatively easily.
For example, such a system enables water flows to be quickly and easily adjusted in relation to increasing or decreasing heat loads in a workspace, without the need for specialist commissioning skills. Similarly, in a situation where heating and cooling are provided by a heat pump, use of an addressable valve will enable water volumes to be adjusted in direct response to changes in heating and cooling loads throughout the year. In this way, the same coil can be used for heating or cooling for most of the year, adjusting water volumes to compensate for the varying outputs of the heat pump.
In addition, this approach facilitates major time savings in commissioning. We were recently involved in a project where 320 fan coil units were commissioned using PICVs in just four days.
This enhanced flexibility can also help to reduce maintenance requirements. For instance, many systems now use lower flow rates than used to be the case, requiring a smaller orifice for the water to flow through. This increases the chance of dirt and air becoming trapped. Conventionally, the only way to free any dirt particles larger than the set orifice is to manually open the valves to allow the dirt through. However, with a dynamic system the simple expedient of setting valves to automatically open fully for a few seconds once a week will eliminate blockage problems by flushing through any accumulated dirt particles.
These are just some examples of the potential for addressable pressure independent valves to bring about a real sea-change in how we operate fan coil and chilled beam systems. The technology is available and has been tried and tested in a number of live environments. So now is the time to take control of fan coil and chilled beams to ensure that the building continues to operate at optimum efficiency.
Further information can be found at www.marflowhydronics.co.uk