Engineered Systems Magazine

Cutting The Cord — Wireless Sensors Resolve Problems In Retrofits

August 4, 2006
Accurate temperature sensing is a prerequisite for satisfying tenant/owner expectations for comfort control, and sensor location is critical to accurately measuring temperature. Installation difficulties can make sensor placement difficult, compromising project cost, timing, and quality.

Today, wireless technology is evolving rapidly. Past concerns regarding reliability, battery life, and cost have improved to the point where wireless is a practical alternative to traditional sensors in common applications. As a result, many new wireless zone sensors are now available. According to Frost & Sullivan market data, wireless sensor volume will approach that of wired by 2008.

Retrofits are among the most beneficial applications of wireless zone sensors. Wireless solves many initial installation difficulties and allows easy, low-cost relocation when the space is reconfigured.

Problems Wireless Addresses

Wireless can overcome three common problems: changing floor plans, challenging architecture, and high-risk projects.

Changing floor plans. Leased properties, offices, retail spaces, and other properties where floor plans are frequently moved require pulling new wire to, and re-terminating wire at, the desired location. With wireless, this project labor time and cost is eliminated.

Perhaps the most obvious situation where wireless sensors solve a problem is when sensors need to be moved. Copy machines, refrigerators, and other common equipment and appliances can cause inaccurate sensing. Initial placement may not accurately measure the space. Wireless enables flexibility to relocate a sensor with minimal effort and cost. Among the most beneficial uses of wireless zone sensors is in retrofit applications. Wireless solves many initial installation difficulties and allows easy, low-cost relocation when the space is reconfigured.

Challenging architecture. A building’s architecture and structure can pose wiring challenges for a number of reasons. Challenging elements include stone, brick, or glass walls, and atriums. “Cube farms” with large open areas or panels limiting airflow for wall-mounted sensors can be problematic. In some buildings, restrictions involving historical preservation prevent wiring.

High-risk projects. Tight deadlines and unanticipated surprises in building retrofits can cause cost overruns and missed project deadlines. With wireless sensors, hidden or unknown construction materials or asbestos may not need to be penetrated or removed.

Installing sensors at building startup and very near the point of occupancy is feasible with wireless. This can meet deadlines and minimize construction and painting damage.

A Wireless Future for Sensors and Building Control?

With a rapid adoption curve and resulting economies of scale, the cost of wireless solutions for BAS, including sensors, is expected to continue to decline. At the same time, investment in new wireless developments is high. The industry is investing in solutions that make integration easy. In addition, interoperable solutions like ZigBee™ wireless protocols and power harvesting promise to bring open, interoperable, and battery-free wireless solutions in the not-so-distant future.

Conclusion

Wireless zone sensors are a viable alternative to wired sensors in retrofit applications today. With the installation and control advantages, wireless may become the expected solution in retrofit applications in the near future. Faced with any of the challenges in the attached checklist, the building staff or team should ask the HVAC or controls supplier to propose a wireless option. Since wireless is approaching parity with wired on total installed cost, specifiers and estimators should consider and evaluate wireless as an alternative if there is the slightest indication for use — both in retrofit applications and in new construction. IBT

Sidebar: When To Cut The Cord?

A checklist on when to consider wireless in retrofit projects:
  • Difficult construction materials such as stone, brick, glass, or concrete block
  • Historic properties, since many present preservation restrictions
  • Atriums, where wiring is unfeasible
  • High construction costs, especially in markets with notably high labor rates and stringent code requirements
  • High churn properties, such as spaces that undergo frequent reconfiguration, or renovations such as leased properties, offices, and retail space
  • Precise temperature control properties where occupant comfort or high-precision processes are critical to occupant comfort or product quality, and where wireless can increase the chances for optimal sensor placement
  • Fast-track projects encountering occupancy deadline pressure