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What’s the Deal with Gas Valves? Explore Functions and Types

gas valves
Photo by Freepik

One thing to consider if your heating system, like a furnace, stops is a malfunctioning gas valve. 

Furnaces frequently shut off due to power outages, filthy air filters, and improper thermostat settings. Once these plausible causes have been ruled out, take into consideration a gas valve problem. Gas valves are used to manage and regulate the flow of gases in your heating systems. They come in a range of metal or plastic materials that are suitable for the pressure and media control specifications.

In this post, we’ll discuss gas valves, the different types, and how they affect the efficiency of your house’s heating system.

What Are Gas Valves?

A gas valve is a critical component of a gas-powered heating system. Its primary function is to control the flow of natural gas or propane to the furnace burner, regulating the amount of fuel that is burned to generate heat for the home. The gas valve is typically controlled by the thermostat, which signals when heat is needed.

Modern gas valves often include safety features such as pressure regulators, flame sensors, and automatic shut-off mechanisms to ensure safe operation and prevent gas leaks or other hazards. These valves are crucial for maintaining a comfortable and safe indoor environment in homes during colder months.

What Is the Function of the Gas Valve?

When the thermostat calls for heat, the gas valve opens, allowing gas to flow into the burner assembly. The gas is then ignited by the furnace’s pilot light or electronic ignition system, and the burner heats up. Once the desired temperature is reached, or when the thermostat no longer calls for heat, the gas valve closes, stopping the flow of gas to the burner and extinguishing the flame.

  • Regulating Gas Flow —- The primary function of the gas valve is to regulate the flow of natural gas or propane into the furnace burner. By controlling the amount of fuel that reaches the burner, the gas valve determines the intensity of the flame and, consequently, the amount of heat produced by the furnace.
  • Temperature Control —- The gas valve plays a crucial role in maintaining the desired temperature inside the home. When the thermostat detects that the temperature has fallen below the set point, it signals the gas valve to open, allowing gas to flow to the burner for heating. 
  • Safety —- Gas valves are equipped with safety features to ensure the safe operation of the heating system. These features may include pressure regulators, flame sensors, and automatic shut-off mechanisms. Pressure regulators maintain a consistent gas pressure, while flame sensors detect the presence of a flame and ensure that gas is only released when ignition is successful. Automatic shut-off mechanisms can cut off gas flow in the event of a malfunction or dangerous condition, such as a flame failure or excessive gas pressure.
  • Energy Efficiency —- By precisely controlling the amount of gas supplied to the burner, the gas valve helps optimize the furnace’s energy efficiency. This ensures that the furnace consumes the appropriate amount of fuel to meet the heating demands of the home without wasting energy.

Different Types of Gas Valves

Gas valves used in home heating systems vary depending on factors such as the type of heating system, efficiency requirements, and control mechanisms. Here are several types commonly used:

  • Manual Gas Valves —- Manual gas valves are basic valves that require manual operation to open or close the gas flow. They typically feature a handle or knob that users turn to adjust the flow of gas. While less common in modern heating systems, manual gas valves are still used in some applications where simplicity and reliability are prioritized.
  • Millivolt Gas Valve —- Millivolt gas valves are commonly used in older or simpler heating systems, such as standing pilot furnaces or gas fireplaces. These valves are operated by a small electrical signal generated by a thermocouple or thermopile. The thermocouple or thermopile produces a millivolt electrical current in response to the heat of the pilot flame, which is used to control the gas valve’s operation.
  • Standing Pilot Gas Valve —- These valves are typically found in older furnaces and boilers. The pilot flame is kept lit at all times, ready to ignite the main burner when the thermostat calls for heat. While less energy-efficient than electronic ignition systems, standing pilot gas valves are known for their reliability.
  • Intermittent Pilot Gas Valve —– Intermittent pilot gas valves, also known as spark ignition gas valves, use an electronic ignition system to ignite the pilot flame only when heat is needed. When the thermostat signals the need for heat, the electronic ignition system generates a spark to ignite the pilot flame. Intermittent pilot gas valves are more energy-efficient than standing pilot valves.
  • Direct Ignition Gas Valve —- Direct ignition gas valves, also known as hot surface ignition gas valves, utilize a hot surface igniter (HSI) to ignite the main burner when heat is required directly. The hot surface igniter consists of a silicon carbide or silicon nitride element that heats up rapidly when an electrical current passes through it. Direct ignition gas valves are efficient and reliable, making them common in modern high-efficiency furnaces.

Photo by Freepik
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Frequently Asked Questions

How do I know if my gas valve is faulty?

Common signs of a faulty gas valve include difficulty starting or maintaining the furnace flame, inconsistent heating, unusual noises during operation, or a noticeable smell of gas. If you suspect an issue with your gas valve, it’s crucial to have a qualified technician inspect and diagnose the problem to ensure safe and proper operation.

Can I replace a gas valve myself?

Gas valve replacement is a complex task that should be performed by a licensed HVAC technician due to safety concerns and the need for precise installation and calibration. Attempting to replace a gas valve without proper training and expertise can lead to gas leaks, fire hazards, or other dangerous situations.

Are there safety features built into gas valves?

Yes, modern gas valves often include built-in safety features to prevent gas leaks, flame failures, and other hazards. These features may include pressure regulators to maintain consistent gas pressure, flame sensors to detect the presence of a flame, and automatic shut-off mechanisms to stop gas flow in case of emergencies.

What should I do if I smell gas near my furnace?

If you detect the odor of gas near your furnace, it’s essential to take immediate action to ensure safety. First, evacuate your home and avoid using any electrical devices or open flames. Next, turn off the gas supply to your furnace if it’s safe to do so. Finally, contact your gas utility provider or emergency services to report the gas leak and seek professional assistance to address the issue promptly.


Heating systems would not operate safely or effectively without gas valves. They keep the gas system’s pressure constant, guarantee that gas flow is properly regulated, and avert possible mishaps. For the gas system to operate as efficiently and safely as possible, gas valves must be installed and maintained correctly. At Hansen’s Plumbing, our skilled HVAC specialists can assist you in resolving any heating-related problems. Contact us today.

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