A flow meter is an instrument that measures the volume or mass of air or water moving through an HVAC system in real-time. Flow meters provide critical data for system balancing, performance monitoring, and energy management. Common types include turbine meters, orifice plates, and ultrasonic sensors, each suited to different applications and accuracy requirements.
Types and Measurement Technology
Turbine flow meters measure airflow up to 5,000 CFM with ±2% accuracy, using a spinning rotor that generates electrical pulses proportional to flow rate. Orifice plate meters create pressure differentials to calculate flow indirectly and cost under $500. Ultrasonic meters offer non-invasive measurement through ductwork without pressure drop, ideal for existing installations requiring retrofits.
System Applications
Flow meters enable demand-controlled ventilation, system commissioning, and continuous commissioning programs. They verify that outdoor air intake meets codes (15 CFM per occupant minimum), balance supply and return flows, and detect equipment degradation. Installation in main supply plenums provides 0.5-1 inch WC permanent pressure loss.