Gas-fired whole-house hot water and steam boilers use natural gas or propane to provide hot water or steam for heating. All units are gravity vented and require connection to an exhaust pipe or chimney to release fumes. These boilers provide the primary source of heat throughout a house.

These ignition transformers ignite the oil in hot water and steam boiler burners. They transform the incoming electrical power to a level high enough to ignite the oil droplets in the burner, producing a flame in the heating chamber that allows the water in the boiler to heat up.