Product Spotlight: Building Automation and Controls
LonWorks product web site presents 1,500 products from 50 manufacturers. For each product, the site supplies product descriptions, data sheets and user manuals. Users can view pricing and order online. (from Engenuity Systems) RS #12 Zone pressure sensor measures and reports duct/building static pressure, room-to-room differential pressure and air velocities and volumes.
LonWorks product web site presents 1,500 products from 50 manufacturers. For each product, the site supplies product descriptions, data sheets and user manuals. Users can view pricing and order online. (from Engenuity Systems)
Zone pressure sensor measures and reports duct/building static pressure, room-to-room differential pressure and air velocities and volumes. The unit relies on a silicon, piezoresistive sensor that is designed specifically for low pressure. (ZPS from BAPI)
HVAC controllers are available in two new models that provide control for smaller point count installations. One model is standalone for fan coil units. The other option is factory-mounted and wired to an actuator for direct-mount VAV applications. (Talon HVAC controllers from Staefa)
Site management controller captures, prioritizes and queues alarms from devices on a local network working with interoperable LonWorks devices that support the LonMark standard alarm network variable. Alarms are displayed the moment they are received, logged into a history database and forwarded via e-mail. (SMC-300 from Circon Systems)
Data loggers are available in two models: one for temperature and the other for both temperature and humidity. The units feature a push-to-start button, allowing users to decide when to start logging data, so that unusable data is eliminated. The loggers feature data storage of 32,512 sample points. (SR- and TR-200 from Dickson)
Head pressure controllers for air conditioners and heat pumps reduces energy costs by adjusting fan speed of the condenser. Fans are given an initial hard-start at full speed for 10 seconds and then slowed according to required condenser temperature. (from EDC International)
Wireless fume hood sensor uses RF transmitter and receiver to detect, calculate and communicate sash position in less than one second. Designed for horizontal sashes, the device eliminates the need for exposed wires in laboratory environments. (from Phoenix Controls)
Global controller features 32-bit processor and 10/100 Mbps Ethernet connections. The BACnet-compliant unit supports energy management system features, including optimum start, demand limiting, tenant billing, trend logging, scheduling and alarming. (BTI-100 from Alerton Technologies)
Controller platform communicates via Ethernet to facilitate integration of building automation systems with IT and other services. A web server within the controller enables access of control settings and data through a standard web browser. (IQ3xcite from Novar)
Controls system is backward-compatible with previous generation systems manufactured since 1986 and forward-compatible using the BACnet protocol. System designers can choose from five DDC controllers. (MACH by Reliable)
Heat pump controls are offered in programmable and non-programmable models. Key features include intelligent recovery, smart sensing and humidity control. The control keeps auxiliary heat off, unless the compressor cannot maintain sufficient heat. (Medallion series from PSG)
BACnet workstation is fully web-based, providing users with the ability to view, manage and control multi-vendor BACnet systems and devices. The system supports dynamic graphics, alarm and event logs, status summaries, historical trending and control parameter changes. (Supervisor by Tridium)
Programmable field controller combines fieldbus coupler functionality with that of a PLC. The user can store and execute programming locally, while still communicating I/O signals to and from the network. Program execution continues, even if the fieldbus connection is lost. (PFC from Wago)
Quick Hit: Valves
Valve selection and application can be confusing for young engineers. There are numerous types and styles of valves available. Different materials and pressure ratings add to the complexity of proper valve specification.
Valves in general provide two main functions. The first is to isolate or stop flow. The second is to balance or regulate flow. The valve may be manually controlled or operated through a control system. The table below offers a quick reference guide to the various types of common valves and their characteristics.
The most basic style of valve is the gate valve. A gate valve functions just like its name. A plate, or gate, moves vertically within the body of the valve to either allow or stop flow. Just like a knife cutting a cake, the gate of the valve cuts through the flow of the fluid in the piping system.
Globe valves utilize a round plate or disc that operates open and closed against the flow of fluid in the body of the valve. The entire surface of the disc is in contact with the fluid flow through the valve. As the valve closes, the entire circumference of the disc is in contact with flow and restricts the flow. The design of the valve allows it to be used for regulation and flow throttling as well as for isolation of flow. Operation of a globe valve is similar to that of a gate valve (multi-turn). For those same reasons, ball valves—and for larger sizes, butterfly valves—are specified more commonly today than globe valves.
Butterfly valves utilize a round disc inside the body of the valve that rotates 90° perpendicular to the flow of fluid in the valve. The design of the butterfly valve is similar to that of a single-blade round-duct volume damper. The entire surface of the disc inside the valve is in contact with the fluid flow through the valve.
The most common style of valve specified today is the ball valve. True to its name, a ball valve utilizes a sphere, or ball, in the body of the valve that rotates 90° perpendicular to the flow of fluid in the valve. The ball has a hole machined through the center that is either positioned parallel to the direction of flow, allowing flow through the valve. When rotated perpendicular to the direction of flow, it stops flow through the valve. Like a butterfly valve, a ball valve operates from open to closed with only 1/4 turn of the valve handle.
Ball valves have the advantage over gate valves and globe valves because of the quick operation of the valve and the ability to see at a glance whether the valve is open or closed. The ball is also self-cleaning, enhancing the life and reliability of the valve. Ball valves have almost completely replaced the use of gate valves and globe valves in water system applications in new buildings.