Building Management

Build a Firm BMS Foundation with Field Devices

As the Three Little Pigs discovered, paying attention to building basics is important. Failing to do so can have unpleasant – and potentially disastrous – consequences. On the other hand, getting the fundamentals, like the foundation, right leads to a happy outcome, at least for those in the building.

This lesson is applicable to today’s modern smart structures. To get the most out of a Building Management System (BMS), start with the fundamentals: sensors, valves and actuators. Collectively, they’re referred to as field devices, and they’re the foundation for a BMS. To maximize the performance and resulting benefits of a BMS, its foundation has to be strong.

Sensors measure the temperature, relatively humidity and carbon monoxide (CO) in the air in a room or in ducts that bring climate controlled air to a room. Sensors may also enable fan speed control, monitor differential air pressure, or detect smoke.

By providing an early fire alert, the last capability improves safety, as does detection of unsafe CO levels. The other capabilities allow a BMS to ensure comfort while improving energy efficiency, an important point since HVAC accounts for more than 40 percent of a building’s energy consumption. For example, a sensor makes it possible to independently spot when filters need changing. A sensor may also enable an infusion of fresh air into a room on an as-needed basis instead of some rigid, energy wasting schedule.

In the case of water, sensors measure temperature. An accurate determination of this performance critical parameter means that water arrives where it’s needed in the best possible condition for heating or cooling.

As for valves and actuators, they control the movement of air and water. In the old days, this seemingly simple task might involve two or more devices. One would act as an on-off switch while a second – and possibly third – balanced hot and cold inputs. The combination resulted in an output stream at a desired temperature. However, the use of multiple devices lengthens commissioning time, increasing system cost. Extra devices can also end up hurting energy efficiency. Each added valve or actuator represents another potential source for energy seepage, particularly if sealing isn’t tight.

In many existing buildings, the odds of an imperfect seal are actually pretty good. After all, field devices, like a building’s foundation, are in use a long time. Indeed, it’s not uncommon to find decades old field devices still on the job. In terms of technology, such devices are ancient. They also may not be that reliable. One result may be inconsistent and unpredictable air and water temperature, which makes a building less comfortable and energy efficient.

An example of the impact new technology can have is found in the latest pressure independent control valves, or PICVs. These devices combine control and balance valves into one, saving installation time and cost. Because one PICV replaces two or three older devices, commissioning time is reduced. Newer technology – and fewer devices – means that seals are tighter and there is less energy seepage.

A final point about this new technology is that it is compact, thanks to advances in the valve and actuator and also because there is now one device instead of many. Compactness is important. Perhaps as much as three fourths of the time new field devices will be installed as a retrofit or in-place upgrade. Thus, typically at least some of the old piping and ductwork will be present and installers may have to work in tight and constrained spaces. In this case, size matters, with smaller and more compact being better.

So, in smart buildings getting the basics right is important. Giving a BMS a foundation of up-to-date field devices will allow it to make a building as efficient and perform as well as possible. And that’s no fairy tale.

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