What flow sensor types are used in HVAC hydronic systems?

The most common flow sensor types in HVAC hydronics are differential pressure devices (orifice plates, venturis, and Annubar averaging pitot tubes), turbine/paddlewheel meters, vortex shedding meters, electromagnetic (mag) meters, and ultrasonic meters (both transit-time and Doppler types). Electromagnetic flow meters (e.g., Belimo's ultrasonic flow sensors on Energy Valves) are increasingly popular for building automation because they have no moving parts, no pressure drop penalty, and can handle glycol mixtures accurately. Vortex shedding meters work well for steam flow measurement but require minimum velocities of about 0.3 m/s in liquids. For most chilled and hot water BMS applications, insertion-type electromagnetic or ultrasonic meters provide the best accuracy (±1–2% of reading) and turndown ratio (50:1 or better) with minimal pressure loss.