Consumer Guide to Oil Fired Boilers

Btus

• Heating systems such as oil-fired boilers are typically sized in British thermal units, or Btus. A Btu is the amount of energy that raises the temperature of 1 pound of water by 1 degree Fahrenheit. The input Btu combined with the furnace efficiency produces the output Btu. For example, a unit with 100,000 Btu of input and 80 percent efficiency produces 80,000 Btu of output. One with 95 percent efficiency produces 95,000 Btu and is more cost-effective. In general, areas with colder climates such as Maine require boilers with higher Btu than areas with mild climates such as Florida.

Sizing

• Oil-fired boilers that are too small will not produce enough heat to make a house comfortable. Those that are sized too large will cycle on and off too frequently and use up too much energy. The most accurate way to estimate the size of a boiler is to hire a contractor who uses Manual J, “Residential Load Calculation,” produced by the Air Conditioning Contractors of America. This document estimates heating systems by considering the local climate; size and shape of the house; orientation of the structure to the sun; insulation; number of windows, skylights and doors where heat can escape; number and ages of occupants; and comfort preferences.

Fuel

• Oil-fired boilers generally use heating oil refined from crude oil. Other alternatives include renewable fuels such as biodiesel or heating oil blended with biodiesel. In any case, the boiler requires an oil storage tank installed according to local building codes by professionals. The tank requires periodic inspection, typically at the same time as the oil-burner maintenance checks. It must be away from any vegetation and debris, and not contact any metal objects. It must not smell like oil, which may indicate corrosion or leaking and require repair.

Retrofitting

• To save on the cost of replacement, an existing boiler can be retrofitted with more energy-efficient features. The most common is adding a vent damper that can close off a boiler vent when the boiler isn’t firing. This prevents heat loss through a chimney. More effective is replacing the entire burner with a flame-retention burner. This blocks airflow through the chimney when the boiler isn’t running, which can save up to 20 percent in fuel costs, according to the U.S. Department of Energy.