Basics Of How Your Kitchen Range Works
Not all ranges look the same, but all of them feature a stove top and over, which operate on similar principals. In this video we will address how a gas range operates as well as potential problems you may encounter. Each surface burner knob on the stove top controls a burner valve. When the know is turned to the light position, the valve opens, allowing gas to flow from the manifold.
As the gas travels through the burner tube, it is directed into the venturi (Venturi effect on wikipedia), where it combines with air to create the proper mixture necessary for combustion. At the same time, the spark switch closes, allowing 120 Volts of alternating current to travel to the spark module which produces high voltage pulses to all of the electrodes. The pulses cause a spark to occur between the electrode and the grounded burner cap.
The gas and air mixture at the burner head is ignited by the spark and a blue flame with an occasional yellow tip is produced. Common problems that occur with this type of electronic ignition system are the electrodes sparking continuously, sparking intermittently or not sparking at all. If the electrodes spark continuously, one or more of the switches has probably shorted closed. A short is usually caused by liquid getting into the switch.
“If this happens, you should unplug the appliance and the give the switches time to dry out,” is what I was told by Mike at Appliance Masters in Tucson (http://appliancerepairtucsonaz.org). If the electrodes are still sparking continuously, once the appliance is plugged back in, one or more of the switches has probably failed and will need to be replaced. If the electrodes spark intermittently, there is a high probability that the module is defective and will need to be replaced.
If one or more of the electrodes fails to spark at all, the cause could be a defective switch that prevents the voltage from reaching the module. The module could also be defective in fail to produce the high voltage pulses to one or more of the electrodes. Finally, the electrodes themselves could be damaged. To help determine this, you can inspect the electrodes for cracks.
A gas oven ignition system consists of three basic components: the oven control, the igniter, and the oven safety valve. The oven control may be switched based with a thermostat and a sensing bulb assembly or an electronic control board that works with an oven sensor. When you select the bake or broil function, the control sends 120 Volts of alternating current to the appropriate igniter.
The igniter is wired to the safety valve and as the igniter starts to get hot, it draws an increased current or amps to the valve. Inside the valve is a bi-metal arm that reacts to the heat generated by the amps. Once sufficient amps passed through the valve, the arm flexes and opens, releasing gas into the oven burner tube. The gas travels through the burner tube until it reaches the bake or broil igniter.
By this time, the igniter temperature is over 2.000 degrees Fahrenheit, so the gas is easily ignited and the appropriate burner will begin to heat. The igniter remains on to keep the safety valve open until the over reaches the designated cooking temperature. The temperature is monitored by the sensing bulb on the thermostat or by the oven sensor. When the selected temperature is reached, the oven control shuts off the voltage to the igniter. The arm inside the safety valve closes, shutting off the gas supply to the burner.
This cycle repeats throughout the cooking process to maintain the proper temperature. Keep in mind, the cooking temperature designated by the control is only an average. The actual temperature will fluctuate throughout the cycle. Convection ovens will reduce this fluctuation by using a motorized fan with or without its own heating element to circulate the heated air evenly throughout the oven cavity.
If any of the ignition system components fail, the oven will either not heat at all or heat improperly. The component that most commonly fails is the igniter. If your over is bake or broil burner is not working, remove any covers or shields and observe whether or not the burners igniter is glowing. If the igniter is glowing, but the burner has not been lit after ninety seconds, there is a high probability that the igniter has weakened and it’s unable to draw the proper amps to open the safety valve and light the burner.
In this case, the igniter should be replaced. If the igniter is not glowing, you should test both the igniter and the safety valve to determine if one of them has stopped functioning. If one or both of the burners are still not working, the oven is overheating or the temperature is off by more than forty degrees Fahrenheit, once preheated, the oven control is probably defective. If your oven has a switch base control with a thermostat and sensing bulb, the entire assembly will need to be replaced. If your oven has an electronic control, the oven sensor can be tested to determine whether the sensor or the control board is the source of the problem.