Sizing

• The U.S. Department of Energy recommends that for the most accurate sizing calculation for oil furnaces, contractors should use “Manual J: Residential Load Calculation,” published by the Air Conditioning Contractors of America. Factors for this calculation include the local climate; the size, shape and orientation of the house; the window areas, locations and types; the insulation levels; the number and ages of occupants; the heating levels for comfort; and the energy use by other appliances that can give off heat. If new ducts are part of the installation, contractors can consult “Manual D: Residential Duct Design” from the same organization. Following are three typical examples of modern oil furnaces and their sizes.
  
  

Highboy Oil Furnace

• The Highboy Oil Furnace takes 90,000 BtuH (British Thermal Units per hour) and releases 74,000 BtuH. It has an Annual Fuel Utilization Efficiency or AFUE of 83 percent, which puts it at the more efficient end of oil burners. It measures 54 inches high by 19.5 inches wide and 30.625 inches deep, and requires a supply opening of 18 inches wide by 19.625 inches deep, and a flue that is six inches in diameter. As with most oil furnaces, it uses 120 volts of electricity. It boasts a limited lifetime warranty on the heat exchanger, and a five-year warranty on other parts.
  
  

Lowboy Oil Furnace

• If clearance to the ceiling is an issue, then the Lowboy Oil Furnace only measures 42 inches high by 25 inches wide by 61.125 inches deep. It has an input of 196,000 BtuH, an output of 245,000 BtuH and an AFUE of 80 percent. The supply opening must be 24.5 inches wide and deep, and it requires a flue of eight inches in diameter. The heat exchanger also has a lifetime limited warranty, with a five-year warranty on other parts.
  
  

Mobile Home Furnace

• For small installations such as in mobile homes, the Mobile Home Furnace puts out 54,000 BtuH from an input of 66,000 BtuH, with an AFUE of 80 percent. It measures 76 inches high by 19.5 inches wide by 24.75 inches deep. It requires roof jacks for venting and a separate two-inch polyvinyl chloride combustion air inlet. It costs $1,573 and features a 10-year limited warranty on the heat exchanger and a two-year limited warranty on all other parts. This is according to Ingram's Water & Air Equipment (see Reference section), with prices accurate at the time of publication.