Phoenix Controls Corp.

Oct. 19, 2006
Cleanroom Air Flow Controller Curbs Drift, Cuts Costs

The Traccel Room Controller is designed for variable air volume (VAV) temperature control, in applications where consistent directional airflow is critical, either into or out of a given manufacturing space. Developed by Phoenix Controls, the controller maintains an offset between the volume of air supplied into and exhausted from the space to maintain consistent room pressurization and directional airflow.

The device’s design differs significantly from traditional VAV controllers. For one thing, its geometry is entirely different: it’s a cone, rather than a blade assembly, explains marketing director Rick Stakutis. “Rather than measuring in the field, we decided to measure air flow at different areas in the cone, near the venturi, so that measurements can be made accurately at the factory,” he says. The cone assembly is spring mounted to the line assembly so that, as static pressure changes, the cone assembly changes. The regulator takes over in the field, Stakutis explains.

In traditional VAV control devices, one measures the air going through them, but it can be difficult to maintain the right setpoint. The devices get dirty over time, and measurements drift, as a result, maintaining pressurization can be a big challenge, Stakutis says.

Traccel downloads 48-point flow characterization curves for the supply and exhaust valves in the factory to the controller’s on board microprocessor, which uses this data to control flow tracking between the two valves. The device maintains directional airflow by modulating the exhaust valve based on the known position of the supply valve, and applying a design flow offset between the two.

Easy installation and control

Historically, you put controllers on valves, one for each area — for example, one for the laboratory, another for animal holding areas, and another for biocontainment areas. A huge amount of interfacing is required, as sensors must be connected as well as alarms from incubators or refrigerators, to the valve that runs the fume hood.

Traccel takes advantage of the idea of metering air flow, so that it doesn’t require separate interfaces. This brought the price point down significantly. In addition, one controller can be used for multiple valves. Traccel follows the Echelon LON mark protocol and runs on an Echelon network to pass info from that room

In addition, Traccel can be integrated with a fieldbus back to anything that talks LON. We work with Honeywell, Johnson and other vendors. Both the nodes on Traccel and other products can pass information to gateway computers using BACnet.

The Accel II venturi valve (above) is based on a simple, mechanical design and uses closed-loop control to ensure that set points are maintained. It is a critical part of the Traccel VAV system (below), which allows single controllers to be used for two or more valves.