HVAC technicians, not electricians, usually replace furnace parts and repair furnaces. HVAC stands for heating, ventilation and air conditioning. HVAC technicians are not electricians; they are individuals trained in servicing heating and air conditioning units.
Electricians are trained specifically in electrical operations. There are many different types of furnaces that are fueled by gas, oil, wood and various types of alternative fuels. HVAC technicians are trained in the nuances in each type of furnace and are better qualified to diagnose furnace problems and obtain the proper parts for repairs. Like the training to become a repairman, HVAC repair training consists of a combination of classroom and field work in the form of an apprenticeship.