This system is popular with many contractors for providing a complete zoned Hydro-Air™ Heating system using a boiler instead of a water heater. Often because of the load, larger homes cannot use a single gas fired appliance to do the job. When this is the case, the system can use a larger output boiler and still provide full heating and Domestic Hot Water. An alternative would be to use a Dual Water Heater System to get adequate capacity for heating & hot water.