August 2012

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Wireless for Fume Hoods

The energy savings – and environmental benefits – of eliminating open fume hood door situations can be huge. 

Todd Hanson
Director of Wireless Solutions
Honeywell Sensing and Control (S&C)

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A common fixture in industrial, educational, scientific and medical lab settings: fume hoods are ventilation devices designed to limit exposure to hazardous or noxious fumes, vapors and dusts. Typically a large cabinet enclosing five sides of a work area, fume hoods are either designed to be ducted or re-circulated air. Ducted fume hoods maintain constant or variable airflow to expel compromised air through an outside vent while recirculation units recycle air through carbon type filtration. Such airflow can be reduced through variable speed fans, but minimum airflow must be maintained at all times per regulations.

Commonly, fume hood doors are left open when not in use and pull conditioned (interior) air into the fixture and expel it, creating energy inefficiencies – and expensive heating or cooling bills. A single hood with the sash left ajar for 24 hours can consume as much energy as a single family home in the same amount of time. Several universities have reported annual energy losses of over $2500 per open hood. The energy savings – and environmental benefits – of eliminating open fume hood door situations can be huge. 

Due to safety concerns, fume hood doors cannot be closed automatically. To solve this problem, one major university installed a wireless solution that would send out a notification if a fume door was left open. A wireless switch placed on fume hood doors communicates wirelessly to a receiver, which in turn sends status data through an existing Ethernet infrastructure to a local server.  A server program then facilitates cloud access.  A cloud message of individual fume hood status is communicated via email, text or Smartphone or mobile device app. Once received, someone can be dispatched to physically close the open hoods.

VAV Hood Operation 

CAPTION - High performance, Variable Air Volume (VAV) Hoods rely on Honeywell Limitless™ switch hood monitors to reduce heating and air conditioning operating costs.

The wireless system was easy to install, inexpensive and industry officials predict an ROI of less than one year due to energy loss savings alone. The university, which runs approximately 1000 vented fume hoods, anticipates nearly $1.5 million/year in energy savings.

How Wireless Limit Switches Work

The development of the 802.15.4 Low-Rate Wireless Personal Area Network (LR-WPAN) has opened up new ways to use wireless, as little or no underlying infrastructure is needed to adopt the technology. This translates to affordable installation costs as long cable runs and complicated wiring are eliminated. The absence of wiring and moving parts increases system reliability, decreases downtime and reduces maintenance.  In fume hood applications, there is no additional recertification required because there is no physical modification to the fume hood or its controls.

Wireless Limit Switch

CAPTION: On the fume hood, a wireless limit switch can indicate whether the hood door is open or closed. The status is then provided via the cloud to a computer or to a Smart device.

The system can be a standalone monitoring solution using existing infrastructure or it can be tied into the existing building management system.

Every network, and each switch within the network, has a unique identification number, making it easy to establish the status of the various fume hoods located throughout a facility. These identification numbers, along with unique security keys, allow a switch and its associated receiver to encode their signals so that the communications link between them is both private and virtually immune to crosstalk from other switches or networks.

The receiver unit that forms the other half of a wireless switch installation can be designed to support a single switch or multiple switches. For example, the Honeywell Limitless™ Ethernet  receiver can support up to 16 different remote battery-powered wireless limit switches. In addition to switch activation status, the signal strength and battery levels for each individual switch on its network is monitored every 30 seconds, alerting the facility manager to low battery levels or system issues. This allows for preventive maintenance scheduling and active system troubleshooting. Because 802.15.4 is a low power technology, batteries can last for up to three years without replacement.

These wireless switches are packaged in a rugged enclosure making them extremely resistant to moisture, vibration, or chemical exposure. This means they can operate in very harsh environments.

Why Wireless Now for Buildings, Campuses and Factories?

[an error occurred while processing this directive] There’s been a shift in thought processes centered on wireless networks in industry and manufacturing settings. A few years ago, manufacturing designers, builders and engineers questioned the ability, reliability and security of wireless systems within industrial and building applications. Today, with growing knowledge and rising comfort levels with wireless technology, the questions have changed to focus on the return on investment (ROI) that can be achieved with wireless products. Specifically, how much can a wireless system save a company in maintenance, downtime, operational costs, or energy savings?

While cost-savings vary from application to application, there is hard evidence that there are numerous manufacturing and industrial uses for wireless technologies, and that early adopters are increasing bottom line profits as a result. Results include examples of saving $4000 per hour losses during down factory time due to compromised wired systems, while others report saving the cost of 25-feet of wiring, equaling the cost of a complete wireless system.

Since the development of the 802.15.4 Low-Rate Wireless Personal Area Network (LR-WPAN), developers have specified it for countless applications within various industries. 802.15.4  has opened up new doors as little or no underlying infrastructure is needed to adopt this wireless technology. This translates to low installation costs as long cable runs and hard wiring are virtually eliminated. It also makes wireless very cost effective to retrofit applications.

Cutting the Cords

The advantages and flexibility of 802.15.4 LR-WPAN technology are allowing users to eliminate the wires in a variety of applications. From remote, extreme or hazardous environments to environmentally-controlled factory settings, today’s wireless technology can handle the challenge. The reliability, security and robustness are built in.

The only question that remains is, “When are you going to cut the cords in your application?”


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