How Electric Ranges Work

At first glance electric ranges may seem intimidating for the do-it-yourselfer. Mostly because ranges operate on two 120 volt circuits, that equals 240 volts delivered to the surface units, bake and broil elements. Under no circumstances should an inexperienced person attempt to repair a range or oven that is still connected to the electrical supply. In most cases, disconnecting a range or oven from the electrical supply means you will need to unplug the cord attached to it from the receptacle. However, there are some ranges and wall ovens that are hardwired to the electrical supply. Meaning that there is no cord to unplug. The best way to confirm that you have turned off the appropriate breaker to a range or oven, is to open the door to confirm that the light comes on. Then go to the breaker panel and flip the breaker identified as the range or oven. If it is not identified it will be a double breaker since it is using both 120 volt circuits in the panel. Confirm that the lightbulb is off when you return, and as a backup, turn on one of the burners to see if it gets hot.

All ranges have the same basic components. They have surface elements, bake elements and broil elements, that are made up of a resistance wire inside an insulated metal tube. The exception to that is ceramic top ranges. Since the resistance wire can not come in contact with a pan, or human, a surface element used on ceramic or "glass" top ranges is exposed, fixed in an insulated burner assembly. In addition to a bake and broil element, some ranges have an additional convection element outside the oven cavity. This would be considered a true convection oven. Other range manufacturers put a fan in the rear of the oven cavity to blow the air around, and call that convection. A bake element heats the oven cavity and radiates heat upward to cook the food. By the way on most ranges, the broil element is also on during bake. Sometimes it is cycled on and off, and sometimes only 120 volts is applied to it during bake. Although a broil element operating on 120 volts will not get red, it is very important in the baking process for browning foods on top.

The broil element is used to radiate heat directly on the food that is being cooked. When using a broil element, the item being cooked is placed in relatively close proximity to the broil element. On some ranges the broil element will operate properly with the door closed. On other ovens, the door must be open slightly. This type of range has a position built into the oven door hinges, called the broil position. For food to broil, the broil element must stay on and radiate heat downward. If a range has a broil position on the door, and you closed the door during broil, the broil element will cycle off because the thermostat will hit its maximum. Usually this is 550 degrees Fahrenheit.

The surface units on non ceramic top ranges are made up of a resistance wire encased in a metal sleeve surrounded by an insulating material. In most cases 240 volts are applied to the surface units. These surface units are controlled by switches that cycle a set of contacts on and off. In most cases within a surface unit switch, there is a heater wrapped around a bimetal strip that flexes when it gets hot. In fact this means that a surface unit switch can cycle on and off, even if the burner is removed.

Ranges and ovens today have either a timer mechanism, but more often an electronic control. Timers are used to open and close contacts that control bake and self-clean. Electronic controls use low voltage to energize coils on relays, that open and close heavy-duty switch contacts for bake, broil, and self clean.

And finally a word about ceramic cooktops. Pans used on a range that has a ceramic cooktop must be flat. If the pan is not perfectly flat, it will take longer to cook the food, increase the range energy consumption, and diminish the life of the burner. That's because in order for a burner to operate properly on a ceramic cooktop range, it must force the heat through the ceramic material, and then into the pan. This is done by the process of conduction. In other words, the pan is used to conduct the heat away from the ceramic material. If the pan is not flat or has bumps, and only a small amount of the pan touches the ceramic, it will take much longer to cook food, or bring water to a boil. The elements under ceramic cooktops have a high limit thermostat that cycles on and off if it gets too hot. If most of the heat is not being conducted away from the ceramic top into the pan, it will radiate back down and heat up the high limit safety thermostat built into the burner. This will cause the burner to cycle on and off regardless of the surface unit switch setting. Eventually that excessive heat radiating back down into the surface unit will cause it to become brittle along with the wires attached to it.