Which of the following parts is not found in a natural draft furnace?

In a natural draft furnace, the design relies on the natural movement of flue gases through a chimney or vent due to differences in density and temperature, allowing for a passive exhaust system. The role of an induced draft motor is to actively create a draft to assist with the expulsion of combustion gases; this is commonly found in power vented or forced draft systems rather than in natural draft applications.

All the other components mentioned play essential roles in furnace operation. The blower motor is used to circulate air throughout the home, the standing pilot serves as a reliable ignition source for the furnace, and the limit switch ensures that the furnace operates safely by regulating temperature. Since the design of a natural draft furnace doesn't necessitate the use of mechanical assistance for venting the flue gases, the absence of an induced draft motor is critical to understanding how these systems function.