An evaluation of three commercially available technologies for real-time measurement of rates of outdoor airflow into HVAC systems

During the last few years, new technologies have been introduced for real-time continuous measurement of the flow rates of outdoor air (OA) into HVAC systems; however, an evaluationof these measurement technologies has not previously been published. This document describes a test system and protocols developed for a controlled evaluation of these measurement technologies. The results of tests of three commercially available measurement technologies are alsosummarized. The test system and protocol were judged practical and very useful. The three commercially available measurement technologies should provide reasonably, e.g., 20%, accurate measurements of OA flow rates as long as air velocities are maintained high enough to produce accurately measurable pressure signals. When these three technologies are used in HVAC systems with economizer controls, to maintain measurement accuracy the OA intake will need to bedivided into two sections in parallel, each with a separate OA damper. All three of the measurement devices had pressure drops that are likely to be judged acceptable. The influence of wind on the accuracy of these measurement technologies still needs to be evaluated.