Tom Lymn from WindowMaster Control Systems discusses how increasing demand for low energy approaches to ventilation can be supported by the BMS using the latest technology in window automation.
Smarter Buildings using a natural approach
As buildings become smarter, BMS systems are now being called upon to incorporate more and more elements of building monitoring and control. From the old adage, if you can measure it you can manage it, there are now sensors enabling us to accurately understand how our buildings are behaving; Teamed up with a broader array of devices to enable automation of key building functions, we are in a better position than ever to be able to optimise performance of new and existing buildings.
This approach, done intelligently, will help move us toward higher performing buildings measured in terms of comfort, health, productivity and all importantly energy consumption.
As we know natural ventilation has been around for – forever. Our basic understanding of it is clear, and yet delivering it in modern buildings can be challenging. The principle is simple - fresh air, delivered in the right quantities, at the right times can reduce the buildings reliance on Mechanical Ventilation and deliver high levels of comfort and air quality; All while demanding very little energy input… What’s not to like?
In winter we want to deliver enough fresh air to maintain good levels of air quality while avoiding excessive ventilation which could create unnecessary heat loss or discomfort. Equally in Summer we generally want to exchange air at broadly higher levels to extend as far as possible the amount of time where spaces remain comfortable using only Natural Ventilation.
Smarter control strategies for comfort, wellness and energy
Using intelligent strategies like night-time cooling and pre-emptive ventilation can stretch that band of comfortable operation using only natural ventilation and therefore minimise energy use. Subsequently any additional cooling or mechanical systems may only need to be used to clip the extremes and optimise performance where conditions dictate. Making natural ventilation work intelligently to reduce the operating time and load on the mechanical systems can help deliver the optimum balance of fresh air, comfort and energy consumption, all while reducing run times and often the required capacity of mechanical plant.
The challenge with services that have a wide range of control, and that need to react to many variables, is to deliver highly strategic and predictable levels of control which don’t upset their core objectives - good levels of comfort, air quality and energy. With great potential to influence overall building success and client satisfaction, comes great responsibility to get it right. It’s a double-edged sword, and one that with the right technology is more akin to a fencing foil than a two-handed broad sword.
Traditionally window automation has used a mixed range of different manufacturers components. More often than not these include 24v actuators and power supply units, and multiple devices to take inputs from room sensors and a weather station. These components allow the head end to assimilate approximate desired window positions, produce 0-10v outputs sent across field cabling to other devices, which in turn apply basic run time calculations to power motors for moments of a second.
Often this is in the hope that the timed power provided has been sufficient to engage and drive windows somewhere near to the head end’s intended destination. With little or no feedback, often windows may be opened too little, or beyond the control systems expectations. The only feedback provided is via sensors positioned some way from the windows that may indicate that the performance of the space is still failing and that ventilation positions therefore need changing. Several iterations later, windows need to be routinely closed to re-assert any level of confidence of actual window positions.
Smarter components support easier integration and better functionality
Smart buildings need to use smart devices to achieve the best outcomes; Intelligent ventilation needs to use technology that supports accurate control and feedback to optimise performance of such an essential function, and one that can make or break the success of the building, as well as upset or optimise the balance with other services.
New technology like MotorLink controllers support less components; These 24V power supplies sit directly on the BMS network, and enable control of up to 20 windows in independent groups using simple position commands via BacNet or KNX. This makes it possible to control window positions more directly using less equipment, and all importantly to deliver ventilation rates more predictably. These motor controllers can help to reduce field cabling, and simplify system Architecture and control logic.
Often engineers and BMS integrators are given little influence over the actuators being used on the windows. Where this is the case, the controls are configured to operate based on a typical stroke time of the actuators installed, and the controls directly convert the % position commands from the head end into a run time to suit.
Where there is the opportunity to advise on different actuator types, matching MotorLink actuators open up a new world of possibility for true window feedback. Imagine not just powering windows, but talking to them - gaining feedback on true position, override status and health.
This technology also allows the BMS to control windows slowly during automated routines - to make them operate almost silently in the background, or drive them more quickly should they need to prevent sudden rain ingress or for emergency functions like fire.
Devices like this which provide feedback are already becoming the de facto standard in building automation for many applications. Direct communication and feedback not only enhances the potential for more robust control and associated performance, but can also be used as part of building security to verify window closure at end of day, or set precise limits to openings for night cooling.
Knowing when users have overridden automated routines can also help the BMS to resume optimum control, or understand where areas of the building or user preferences are at odds with system setpoints. This can help prompt a review of the control strategy or enable optimisation of other systems like heating or mechanical ventilation that may be working too hard or having their efforts wasted for optimum performance of the building.
Optional Onboard Logic for a packaged approach
To add to this, the very latest control units can be elected to incorporate proven onboard logic offering a packaged solution; It’s now possible for the BMS to instruct controls with NV Embedded to simply GO or STOP without needing to incorporate more complex algorithms into the BMS. Sophisticated logic built into the controls uses information from shared sensors on the network to calculate optimum window positions and to accurately control ventilation for best performance. With additional Cloud functionality, this approach can minimise complexities of the BMS, all while leaning on proven logic to ensure windows are connected, and working to compliment other building services.
For a more in depth look at the potential of Intelligent Natural Ventilation and the technology available, WindowMaster is running a live webinar on Thursday 18th March at 11.30am which is free to register here: