In the world of HVAC, an airflow transducer is a device that converts an airflow signal into an electronic signal for a VAV controller to regulate a damper and provide airflow to a space.
| Price’s new DISIO Airflow Kit (left) adds VAV flow control to the DISIO Display Thermostat (right) | |
When an airflow transducer is used, the VAV controller is said to be pressure independent, where it maintains a constant airflow regardless of changes in the system’s duct static pressure. The VAV controller measures the airflow at the inlet of the VAV box and uses the area of the inlet to calculate the velocity pressure from the flow sensor. From there, the VAV controller will control the internal damper to a specified minimum and maximum airflow to deliver the correct amount of air based on the load calculation for that space.
One common misapplication when it comes to sizing VAV boxes for commercial spaces is to oversize the inlet of the VAV box and then specify low airflows for that space. The intent here is to reduce the amount of air and noise coming through the VAV box and eliminate the requirement for reheating the air. Reheating high volumes of cool, conditioned air is costly and not overly energy efficient.
The issue with this approach is that insufficient airflow will be supplied to the space and the transducer on the VAV controller cannot resolve these low airflows. When the specified airflows are outside the recommended airflow range of the terminal unit, the VAV controller will hunt while trying to adjust the damper to these flows. This will shorten the life of the actuator and create uncomfortable space conditions.
Selecting the correct inlet size for the VAV box within the specified airflow range will result in better control and will provide enough airflow to the space.
| Click to read more about how the DISIO Airflow Kit works with the DISIO Display Thermostat |
Price now offers the new DISIO Airflow Kit for precise airflow monitoring and control. When paired with the sleek DISIO Display Thermostat and control sequence DX-150, the DISIO Airflow Kit will output a 0–2 in.w.g. signal proportional to the differential pressure measured at the inlet, resulting in pressure-independent control of a VAV damper – and a comfortable indoor environment for everyone.
For more information about the DISIO Airflow Kit and the DISIO Display Thermostat, visit our website or email us at controls@priceindustries.com.