How Do Gas Ranges Work?

Most gas ranges are designed with very similar set ups. The information below will help you understand how most gas ranges and ovens work. Before looking at the problems with gas ranges, it is important that you have an understanding of how they work. If you have a gas wall oven, ignore the parts about the cooktop. If you have a separate gas cooktop, ignore the parts about the oven. A range is just a cooktop on top of an oven that shares a gas and power supply.

Gas ranges basically take natural gas or propane and turn it into concentrated heat that you can use for cooking and baking. There are burners on the cooktop and one or two burners in the oven which burn gas that has been ignited by a pilot, spark ignitor, or glow ignitor.

On the cooktop you usually have 4 to 6 burners with grates over them that allow you to cook in pots and pans. Gas flows from the main gas valve to a manifold that has a corresponding number of burner valves. The gas is brought from the burner valve to the burner through a venturi tube. The burner control knobs that you see on the control panel attach directly to the burner valve. This valve controls how much gas is sent to the burner. To get a larger flame, you send more gas to the burner. The venturi tube between the burner valve and the burner allows the gas to properly mix with air for clean combustion. The air and gas mix then flows into the burner where the pilot flame or ignitor ignites it. On models with a spark ignition, there is usually a spark switch attached to the burner valve, a spark module and the spark ignitor. When you turn the valve, the switch tells the spark module to send electricity to the spark ignitor to create the spark to ignite the gas. Almost all older cooktops with unsealed burner units allow you to raise the entire top for cleaning and service.

In order to control how close your food is to the flame, there is at least one adjustable rack in the oven. In the oven, there is at least one burner on the bottom. If there is a broiler below the oven, this is the only burner in the oven. If you have a utility drawer or nothing below the oven, there is probably a second burner on the top of the oven that is used during broiling. The burner is a tubular device through which the gas flows before it’s ignited. It has a lot of little holes on its sides that lets the gas burn and provide heat evenly throughout the oven. The gas gets to the oven burners through a safety valve. The gas safety valve does precisely what the name implies. It prevents gas from being introduced to the burner when there’s a possibility that it won’t get ignited properly. There are a few different variations in their operation, but the purpose is always the same, to prevent accidents, and allow gas to get to the burner when it is safe.

In order for the gas in the oven to burn it needs to be ignited. The most common ignition systems in use currently are the spark ignition and glow-bar ignition systems. Pilot flame systems tend to have hard to find parts.

Many ovens use the glow-bar ignition system to light the oven or broiler. During normal operation, the glow-bar will glow yellow-hot. A weak or faulty ignitor may still glow, but only glows red through orange. Replace a faulty ignitor. Some glow-bar systems have a fuse in the system, under the cooktop or in the console itself. Check for continuity in these systems.

Spark ignition systems use a spark module to generate a high-voltage spark which is used to ignite a pilot light. This module is used for the burners on the stove as well as the burner in the oven. As the pilot light heats a capillary tubes’ bulb liquid, it expands and puts pressure on a diaphragm. The diaphragm then opens the gas safety valve, releasing gas to the burner. This gas then gets ignited by the pilot light flame.

Pilot ignition systems in the oven use a flame sensor to determine whether or not the pilot is lit. This sensor sits in the middle of the pilot flame. The position of the sensor is very important. The pilot flame has two parts to it, the outer yellow flame, and the inner blue flame. The sensor needs to be in the hottest part of the pilot flame, located right at the tip of the blue flame to operate properly. If the sensor detects that the pilot is lit, only then will it allow the gas safety valve to open and let gas flow to the burner.

There are several different systems that manufacturers use to control pilot light systems. The capillary pilot system uses a liquid filled bulb that is connected via a capillary to the gas safety valve or flame switch. When the bulb’s liquid gets heated up, it expands and puts pressure on a diaphragm. The diaphragm then opens the gas safety valve or closes the flame switch. The flame switch system uses hydraulic pressure from the capillary to physically close a switch. This completes a circuit to the gas safety valve. If there is no pilot flame, the gas safety valve will not open. In the hydraulic capillary system, the hydraulic pressure from the capillary physically opens the gas safety valve itself. If there is no pilot flame, the gas safety valve will not open. The millivolt pilot system uses a bi-metal pilot generator. When the copper and steel bi-metal strip is heated, it produces an electrical current. This bi-metal strip generates about 750 millivolts. This current allows the gas safety valve to open. If there is no pilot flame, then there is no current and the gas safety valve will not open.

The oven thermostat is usually integrated with the gas valve for the oven. It is located behind the knob that controls the gas valve. You can often adjust your oven thermostat using a small screwdriver. The adjusting screw is located on the thermostat valve stem. Remove the knob and you’ll see the screw underneath it. You want to turn the oven on and run it through at least two cycles while watching a calibrating thermometer in the oven for high and low temperatures. Adjust the screw as necessary to fine tune the temperature.

In the past, clocks were usually manual and worked with the selector switch and thermostat to set a time for the oven to come on, and a time for it to turn off. Clocks today are usually electronic, and in some cases, have taken over the control functions of the thermostat and selector switch. They connect to an oven temperature sensor to determine what the oven temperature is. The oven temperature sensor is located in the oven and attaches to the clock with high temperature wiring. Then the control sends more or less electricity to the broil and/or bake elements as needed. These types of clock are usually referred to as Electronic Oven Controls (EOC) or Electronic Range Controls (ERC). The keypad that you use to set the EOC, along with the EOC itself can only be replaced, not repaired. On some models the keypad is available separately from the EOC, and on the others it is one integrated part.

Most ranges have a light inside the oven compartment. The switch on the oven door turns the light on when you open it. Some models also have a manual switch on the range top that will let you turn the light on. Some models also have a light on the backsplash with a switch located near or on the control panel.

It is very important to use the proper pan size and pan material for the cooking you are doing. It’s common for people to use over-sized pans, but the outer edge of the pan or pot should be no more than one inch outside of the surface cooking area. Aluminum cooking pans are great heat conductors. Stainless steel by itself is a slow heat conductor, but if other materials like copper or aluminum are sandwiched between layers of stainless steel, it becomes a very good heat conductor. Cast iron heats slowly, but once hot, it cooks very evenly. Glass and ceramic are slow heat conductors but are easy to clean. Porcelain enamel is created when a glassy material is fused with a metal such as aluminum, stainless steel, or cast iron. The heating characteristics depend on the metal used.

Cast iron cooking pans should be seasoned properly before use for ease of cleaning and rust prevention. One way to season a cast iron pan is to rub a thin layer of vegetable oil all over the pan, and heat it up very hot, then just wipe it down with a clean cloth or paper towel after it cools off.

Advertisements

One response to “How Do Gas Ranges Work?

  1. Thank you for this wonderfully complete explanation of gas range operation. One thing that I have always been curious about is the liquid that is the operative hydraulic element in the capillary gas safety valve circuit.

    Thanks again,

    Brian Leeman

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s