The word furnace derives from the Greek word fornax, meaning oven. A household furnace is a major appliance that is permanently installed to provide heat to an interior space. Most people don’t think of their furnace as an appliance within the household. It needs care and regular servicing to assure it will run properly when cold weather arrives. The most common fuel source for modern furnaces in the U.S. is natural gas. Residential furnaces can be classified into four general categories, based on efficiency and design: natural draft, forced air, forced draft and condensing. There are a variety of furnace types to meet your needs and service area. Now is the time to have your furnace serviced or replaced. Call De Hart Plumbing, Heating and Cooling @ 785-341-4193 to schedule a Preventive Maintenance Agreement or to get an estimate on a furnace replacement. De Hart Plumbing, Heating and Cooling, serving Manhattan Kansas, Junction City Kansas and Wamego Kansas.