The hydro pump on an air handling unit, or air handler, circulates hot water between the water heater and the hydronic heating coil. In an air handling unit, a tankless water heater serves as the heat source, providing the home with hot water and heat simultaneously.
Not all air handling units have a hydro pump. As detailed by Allen Bernard, a facility maintenance advisor for Welsh & Colliers International, an air handling unit conditions and circulates air within an HVAC system. The typical components are a blower, heating or cooling elements, filter racks, sound attenuators and dampers. Normally air handlers are connected to ductwork used to distribute conditioned air through a building or home and return it to the unit. Small air handlers, known as terminal units, are usually comprised of only an air filter, coil and blower.
A hydro pump is found on air handling units that are part of an integrated heating and water systems, such as the one manufactured by Rheem. A hydronic air handler features a heating coil rather than electric or gas-fired heating elements. When in heating mode, the hydro pump moves the hot water to and from the coil, thus being critical to the HVAC’s ability to provide heat to a building.