What are furnaces and boilers that use fuel as a heat source commonly referred to as?

Furnaces and boilers that utilize fuel as a heat source are commonly referred to as fuel-fired furnaces and boilers. This terminology encompasses a variety of systems that rely on different types of fuel, such as natural gas, propane, oil, or coal, to generate heat for residential and commercial buildings. By using the term "fuel-fired," it broadly categorizes equipment that does not rely solely on electricity or solid fuels but may include any source of fuel combustion.

Other options like electric furnaces refer specifically to systems that use electricity as their energy source, while solid-fuel boilers denote those that specifically burn solid materials like wood or coal. Gas-fired heaters specify equipment that primarily uses gas as a fuel but does not cover other fuel types that might be used in fuel-fired systems. Thus, the designation of "fuel-fired furnaces and boilers" accurately captures the diverse range of heating systems that operate on various fuel sources.