Below is a list of Coil Heaters manufacturers from Yelm, Washington. Coil heaters are electric heaters that generate heat through the use of heating coils. A heating coil is a device that converts electricity to heat. Heating coils are among the most widely used heat generation materials in existence. Across industry, commerce and in the context of consumer products, heating coils are used to generate heat in buildings, equipment, small appliances and in other applications.