Towards continuous commissioning
Published: 07 June, 2010
Over the last few years there has been increasing pressure on building-services engineers to think ahead and try to build some ‘future proofing’ into their specifications. In particular, there is greater recognition that as buildings change the services often fail to change with them. Post-occupancy performance, therefore, is of growing importance.
This need for greater flexibility in building-services systems is reinforced by the trends within modern workplaces. Working practices have become more flexible — with an increase in hot desking and similar strategies, while rationalisation of property portfolios is generating more staff moves and reconfiguration of workspaces.
Some services, such as lighting, have been addressing this issue for a number of years, using addressable luminaires that can be managed individually or in zones through the front-end PC of a lighting-management system. The result is that lighting can be quickly, easily and inexpensively recommissioned without any need for changes to the hard wiring and with no need for specialist skills.
Unfortunately, the same cannot be said of most fan-coil or chilled-beam systems, even though many of the workspace changes described above often result in higher staff densities and increased cooling loads. This is because traditionally designed systems require an engineer to access commissioning valves in the ceiling void to make alterations to the system.
As a consequence, many building operators choose the path of least resistance, leave the system as it is and try to get by with some coarse adjustment through local controls. Inevitably, this compromises comfort for the occupants.
There is also a requirement by many building operators to introduce low- or zero-carbon (LZC) technologies such as heat pumps. This would generally require alterations to flow temperatures and, therefore, to water flow volumes — again resulting in considerable disruption and expense.
To meet the changing requirements of end clients and achieve ongoing flexibility and efficiency of hydronic systems, we need a different approach. 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 types of re-commissioning exercise.
Remote, continuous commissioning
One of the key factors in moving towards a ‘continuous commissioning’ concept has been the development of addressable pressure-independent 2-port control valves (PICVs) that can be precisely adjusted through a building-management system (BMS) or BACnet system.
This approach opens the doors for a whole new approach to the design and operation of fan-coil systems as 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, creating a dynamic regime that gives building and energy managers far greater control of both energy optimisation and comfort levels.
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, where heating and cooling are provided by a heat pump, 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, when valves are fixed at a minimal position to satisfy the low flow rates that are now commonly required, the orifice may be so small that dirt and air can become trapped. Conventionally, the only way to free 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. All that remains is for building-services engineers and their end clients to recognise the benefits and take advantage of them.
Martin Lowe is technical manager with Marflow Hydronics.
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