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Moving towards continuous commissioning
(written for Water, Energy & Environment)


Re-commissioning traditional fan coil and chilled beam systems to optimise performance can be disruptive and expensive. Martin Lowe, Technical Manager with Marflow Hydronics, explains how new valve and control technologies are enabling a system of ‘continuous commissioning’.

Over the last few years the workplace has become considerably more flexible and this is a phenomenon that is likely to continue. Unfortunately, where there is a fan coil or chilled beam air conditioning system, the likelihood is that the system will not be adjusted in relation to the changes in the conditioned space – potentially compromising both energy performance and comfort.

In addition, the historic inflexibility of such systems makes it more difficult to incorporate low or zero carbon heat sources, such as heat pumps. However, as discussed in more detail below, this situation is now changing and energy managers need to be aware of the potential arising from new valve and control technologies.

The dynamic nature of the workplace is driven by a number of factors including routine churn, the increased popularity of flexible working practices such as hot desking and the rationalisation of space usage. These factors can often have the effect of creating denser populations of staff in one area of a building, while other areas are used less.

All of which means that the heating and cooling demands in a particular space can vary considerably and, while local controls may provide some coarse adjustment of such systems, this will be limited by the way the system was configured during commissioning. Clearly, the ideal response is to re-commission the system in line with the new requirements but with conventionally designed systems this is disruptive, time-consuming and expensive. Little wonder, then, that many organisations choose compromise as the path of least resistance.

In the last couple of years, however, new technologies have been applied to fan coil systems that allow systems to be re-commissioned from a remote PC, thus minimising the disruption of accessing the ceiling void and facilitating a system of ‘continuous commissioning’. Potentially, this creates a system that is as dynamic as the space it is serving.

Remote commissioning

One of the key factors in this respect 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.

This approach opens the doors for a whole new approach for the design and operation of fan coil and chilled beam systems as the valves are no longer ‘fixed’ and difficult to adjust. On the contrary, they can be quickly and easily adjusted to suit different circumstances, 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, 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.

This enhanced flexibility can also help to reduce maintenance requirements. For instance, when valves are fixed at a minimal position, the orifice may be so small that dirt and air can become 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 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 key is for building operators to recognise the potential and take advantage of it.

 

www.marflowhydronics.co.uk



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