Description HU-921 is designed for humidification/dehumidification and economizer control on packaged roof-top air handlers. Humidity sensors are calibrated over 0 to 100%RH and offer ±3% accuracy over 30 to 70%RH and are temperature compensated from -30°F (-35°C) to 130°F (55°C). By limiting the accuracy over the useable range for controls, significant cost reductions can be provided to OEM manufacturers. HU-921 humidity sensor is designed to handle 100% condensing humidity. The electronics are moisture sealed with an acrylic coating, and the sensing element is protected with an ePTFE (expanded Teflon) filter media. The sensor is designed to be factory or field installed in fresh air hoods, discharge or return air ducts of air handlers. Rugged 20% glass-filled low smoke UL-95-V-0 polycarbonate enclosure, external mounting bracket to accommodate uneven mounting surface, and 1/4” quick disconnect terminals for wire harnesses are some of the features which make the HU-921 a reliable and cost-effective solution for OEM humidity and economizer controls. HU-921 is available with more than 16 types of interchangeable NTC thermistors, precision platinum, nickel or balco RTDs for universal compatibility.