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Teaming up with a flexible friend
(written for Consulting Engineer)

In making better use of the latest valve technologies, specifiers can provide their end clients with far more flexible air conditioning systems. Martin Lowe of Marflow Hydronics explains.

As building operators seek to make their workplaces more adaptable to change, and to make better use of their space by initiating more frequent changes, there is increasing pressure on specifiers to create more flexible building services systems. One obvious example is the use of addressable luminaires so that lighting can be re-configured quickly and simply from a central PC.

Unfortunately, the same level of flexibility is rarely imparted to fan coil and chilled beam systems and it continues to be expensive and disruptive to alter these systems as the workspace evolves. Very often, therefore, the system remains unchanged despite changes in the conditioned space, compromising both energy performance and comfort. In addition, this lack of flexibility makes it harder to retrofit low and zero carbon heat sources, such as heat pumps.

In fairness, it’s only recently that technologies have come onto the market to help specifiers address these issues. But now they’re here, surely it makes sense to deploy them and work towards a situation where ‘continuous commissioning’ becomes the norm.

Amongst the most significant of these technologies are pressure independent two-port valves that can be used in conjunction with programmable controllers. In turn, the use of these has been greatly facilitated by wider use of pre-fabricated manifold systems for fan coil and chilled beam systems. So it’s all coming together – and it’s worth looking at how that happens and the benefits at each stage.

Pre-fabrication itself has undergone a transformation, evolving from simply doing the same work in a different place to producing highly engineered solutions under tightly controlled conditions. Plus, everything required is delivered to site at the same time ready for installation, complete with pictorial instructions to eliminate any language issues.

The manifolds themselves also offer benefits at commissioning as the commissioning engineer can access up to six terminal units from a single location. In fact, with a properly considered control solution the need to revisit each manifold more than once is unnecessary.

Taking this a step further, if the manifold incorporates pressure independent two-port valves the commissioning process can be significantly shortened by using a subtraction technique known as single station balancing (SSB) to identify problem valves. Essentially, if the design flow rates for each individual valve are known, then the total flow rate for that group of terminal units is also known. Consequently, isolating one valve will have a predictable effect on the total flow rate for the remaining valves. If the result is not as expected, there is clearly a problem with that valve, so the commissioning engineer knows where to look in more detail.

Moving to remote, continuous commissioning

Furthermore, if the pressure independent two-port valves are of a design that can be used with programmable controllers to limit the maximum flow rate, this opens the door for a remote commissioning system that will deliver all of the flexibility described above.

The way this works is that the valve is linked to a BMS fan coil or chilled beam controller, and an actuator that can be set from a remote location to the required position to give design flow rates. The controller provides two 0-10V analogue outputs to control the valve actuators while also communicating with other controllers via a BACnet MS/TP network. This enables communications with a PC, so that system software can be configured and updated without directly accessing the controller.

The result is a system that offers the flexibility to carry out what we have termed ‘continuous commissioning’, using a central PC and without disrupting the workspace.

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.

Ultimately, this approach is a significant step in providing building operators with more control of their workspaces and, by making reconfiguration easier to achieve, it will encourage the fine-tuning of services to achieve optimum performance whenever the conditioned space changes.



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