It’s time industry took note of the energy and time-saving opportunities offered by addressable pressure independent control valves, says Martin Lowe of Marflow Hydronic Systems
With the increasing focus on post-occupancy energy efficiency of buildings there is a growing need for building services systems to incorporate higher levels of flexibility. In this way, the building is more able to respond to changes such as higher or lower densities of staff, introduction of renewable energy sources and changes to the thermal performance of the building fabric.
In fact, many building services systems can be reconfigured relatively easily, but this has not traditionally been the case for hot and chilled water systems. This is because with a conventional design, re-commissioning a fan coil or chilled beam system involves visiting each valve in the ceiling void, one by one.
As a result, any such changes can prove costly and disruptive, often resulting in no changes being made to the systems when building use changes. This introduces inefficiencies that lead to wasted energy.
There is, in fact, a tried and tested solution to this problem. Unfortunately, there are many in the specification, installation and commissioning supply chain who prefer to stick with older traditional methods. But if, as an industry, we are to deliver the best solution to our end clients it is essential we take full advantage of such technologies rather than being hide-bound in the old ways.
The new technology I refer to is the addressable pressure independent control valve (APICV), which has not only made it easier to balance variable flow systems, but has also enabled the use of remote commissioning from a PC. This means 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 relatively easily.
Initial commissioning is thus greatly simplified, as is any subsequent re-commissioning. For example, in a recent project using this concept, a 1,400 fan coil system was commissioned in just four days and the building operator will be able to change the system whenever necessary.
To embrace the remote (and thus continuous) commissioning concept it is necessary to understand how it varies from conventional methods. Rather than using traditional balancing valves, rotary PICVs containing internal differential pressure regulators are used. These maintain a constant differential pressure across the valve seats and characterised control valve - the latter providing both a flow limitation function and a temperature regulation function.
Each of these PICVs is fitted with an actuator that is interfaced to a digital controller that may be a fan coil unit controller, a BMS outstation or a dedicated controller. This set-up can then be addressed from a remote PC to give temperature control and flow settings to meet the required duty of each terminal unit. They can even be used to open valves fully for a short period every week or flush through debris and reduce maintenance.
In the commissioning phase, this arrangement facilitates the use of single station balancing, which simulates the system in use and eliminates the tortuous balancing processes typical of many projects. Instead, grouped flow rates are measured at strategic locations, while sections of the system are closed down. This enables the system's performance to be assessed under typical operating conditions and any problems are identified easily.
Just as importantly, with networked control it is possible to set any valve to a particular flow rate, fully open or close any individual valve or apply settings to groups or zones of valves in a single operation.
As well as equipping hydronic systems with the same flexibility as other systems, such as variable refrigerant flow, this approach also makes it easier to introduce low carbon technologies.
In a traditional system this would generate all of the expense and disruption referred to above, but with a continuous commissioning configuration these adjustments are simply a matter of changing settings on a PC.
• The author is technical manager at Marflow Hydronic Systems