If you’ve ever done hands-on work around your plumbing systems or gas lines, chances are you've come across a gas shut-off valve and probably wondered what kind it is before making any mistakes.
Gas shut-off valves isolate a specific gas-burning appliance from the main gas supply. This means you can shut off the gas to that appliance without affecting other appliances.
In this guide, you will learn about the common types of gas shut-off valves used in HVAC appliances, how to identify and handle them safely, and maintenance tips.
Explainer: Common Types of Gas Shut-Off Valves in HVAC Appliances
By the way, you can find high-quality valves for your various HVAC units on Snook & Aderton.
We stock a variety of gas valves, and also valves for controlling refrigerant in air conditioning units and managing water flow in cooling applications. Also, all the valves we carry come with manufacturer warranties.
1. Gate Valves
Gate valves use a flat or wedge-shaped metal disc (the "gate") that moves up or down perpendicular to the flow of gas. When fully raised, the gate allows unrestricted flow; when lowered, it stops flow completely.
There’s usually a round handwheel on top, a vertical stem, and a bulky body (sometimes you see flanged or threaded ends).
HOW TO HANDLE
All you have to do is turn the wheel clockwise to close and counterclockwise to open. However, you need to operate slowly to avoid pressure surges. This type of gas shut-off valve is not for throttling (partial open/close).
ADVANTAGES
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Minimal flow restriction when open.
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Ideal for full-open and full-close situations.
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Durable and reliable in larger systems.
WHAT HVAC SYSTEM USES THIS VALVE?
You will see gas valves mostly on large HVAC gas supply lines, especially industrial systems with steady, high-volume flow needs. They're best used in systems where you don't need to turn the valve on and off a lot.
2. Ball Valve
You will likely find ball valves in your furnace or gas heaters. This one uses a rotating ball with a hole (bore) through the center. When the handle is aligned with the pipe, gas flows; when turned 90 degrees, it blocks flow.
A ball valve has a compact body and a lever handle that turns 90°. The material is often brass or stainless steel.
HOW TO HANDLE
If you’re trying to control a ball gas shut-off valve, know that it uses a quarter-turn operation (fast shut-off).
This is actually easy to handle since all you have to do is just turn the lever perpendicular to the pipe to shut it off.
ADVANTAGES
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Quick and easy to operate.
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Reliable seal.
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Long lifespan, low maintenance.
WHAT HVAC SYSTEM USES THIS VALVE?
Gas shutoff at appliance entry points, such as a furnace or gas heater, is most common in residential HVAC systems. You will also see it more in rooftop unit isolations.
3. Globe Valve
For globe valves, there is a plug (disc) that moves up and down inside a chamber to regulate the flow. The gas changes direction inside the valve, allowing for control over the flow rate. Globe valves usually have a bulky body with a handwheel.
By looking at it, you can notice a spherical chamber (the reason why it’s called “globe”). Also, the inlet and outlet are typically offset.
HOW TO HANDLE
This type of gas shut-off valve works for throttling and flow control. So, you handle it by turning the handwheel, which gradually adjusts the disc.
ADVANTAGES
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It provides better sealing than gate valves
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Excellent for regulating flow.
WHAT HVAC SYSTEM USES THIS VALVE?
If you check boiler gas feeds, chillers, and systems needing flow modulation, you will likely find a globe valve serving as the gas shut-off function.
4. Plug Valve
Similar to the design of ball valves, plug valves have a bore at the center. The difference is that the plug valve uses a cylindrical or tapered plug with a hole in it. Rotating the plug 90° aligns or misaligns the bore, controlling the flow. This one is compact with a simple lever.
HOW TO HANDLE
One common mistake people make with plug gas shut-off valves is overtightening. This gas valve operates on a quarter-turn basis. But it also requires periodic lubrication in high-temp gas systems.
ADVANTAGES
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Simple and compact.
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Quick to operate.
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Good for gas shutoff.
WHAT HVAC SYSTEM USES THIS VALVE?
Most HVAC home appliances do not use plug valves. You will find this type of valve mostly in natural gas pipelines, industrial HVAC zones, and isolation for rooftop HVAC units.
5. Angle Valve
Imagine globe valves with a 90° turn between the inlet and outlet. That’s an angle valve. For gas shut-off, the angle valve is controlled by lifting or lowering a disc against a seat. It also shares a similar appearance with the globe valve. However, the difference lies in its elbow-shaped design.
Most HVAC setups use angle valves when space is at a premium. They are common in compact or corner-mounted setups.
HOW TO HANDLE
It’s simple to operate. You use the handwheel to adjust the gas flow gradually.
ADVANTAGES
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Saves space due to 90° design.
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Good flow control.
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Easy installation in corners.
WHAT HVAC SYSTEM USES THIS VALVE?
Many wall-mounted gas heaters, gas appliances, or units near walls will use angle valves as the gas shut-off controller when straight pipes can't be used.
6. Butterfly Valve
Inside a butterfly valve, there’s a rotating disc (like a butterfly wing) mounted on a rod that opens/closes to allow or restrict flow. The disc turns 90° to shut or open the gas flow. So it goes without saying that butterfly valves aren’t ideal for full insulation.
You can recognize a butterfly gas shut off valve by its large, flat disc inside a short, cylindrical body.
HOW TO HANDLE
To manually shut off the gas on a butterfly valve, simply turn the handle or gear 90 degrees. Usually, this type comes with a locking mechanism. When it’s fixed on large pipes, handling it is easier.
ADVANTAGES
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Compact for large-diameter pipes.
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Quick operation.
WHAT HVAC SYSTEM USES THIS VALVE?
Butterfly valves are the standard gas shut-off valves found in large commercial HVAC gas mains. It is also regular in ventilation gas systems.
7. Thermally-Activated Safety Shut-Off Valve (TASV)
This is the first gas shut-off valve on this list that doesn’t require manual operation. TASV automatically shuts off the gas flow when it senses a specific temperature, typically 212°F or 100°C, depending on the system.
Unlike thermostatic valves that react based on pressure, TASVs act during fire conditions. Depending on the manufacturer, the valve can have a fusible link or thermal element.
HOW TO HANDLE
Fortunately, there’s no manual operation needed during an emergency. The valve operation is automatic.
You only need to replace it after activation.
ADVANTAGES
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Critical safety device.
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Prevents gas-fed fires.
WHAT HVAC SYSTEM USES THIS VALVE?
Many residential or commercial setups with fire safety codes ensure that the gas-fired furnaces, water heaters, and boilers in the building have a thermally activated safety shut-off valve (TASV).
8. Solenoid Valve
If you observe that the gas shut-off valve you’re staring at has a boxy top (which is the coil) on a cylindrical body, with wires coming out of the unit for power, then it’s likely a Solenoid valve.
It’s not manual. Solenoid valves use an electromagnet, called a solenoid, to open and close the valve. When energized, it lifts a plunger to allow gas flow; when de-energized, it shuts the valve.
HOW TO HANDLE
You don’t actually get to ‘handle’ solenoid valves. They are controlled electronically via a control panel or sensor. All you have to do is use the correct voltage.
For example, the ASCO 8040H8 Gas Solenoid Blocking Valve requires an input supply voltage of 120 volts AC at 60 Hz and 110 volts AC at 50 Hz. Although these valves will need occasional cleaning and testing.
ADVANTAGES
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Automated control.
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Integrates with smart systems and safety sensors.
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Very fast operation.
WHAT HVAC SYSTEM USES THIS VALVE?
The way solenoid valves work is that they are pivotal for refrigerant flow. That’s why you see this gas shut-off valve more in refrigeration and air conditioning (AC) systems.
9. Zone valves
Zone valves are used to divide an HVAC system into separate sections, or zones. They control the flow of gas (or water) independently in different parts of the system using electrical or thermostatic control.
Zone valves have compact motor-driven units. Usually, wires from a control panel or thermostat attach them to branch lines.
HOW TO HANDLE
This type of gas shut-off valve is controlled via a thermostat or controller. So, there’s minimal manual interaction. However, you still need to inspect the valve and run electrical testing periodically.
ADVANTAGES
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Precise zone control.
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Increases energy efficiency.
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Works with automation.
WHAT HVAC SYSTEM USES THIS VALVE?
The dominant application of zone valves as gas shut-off valves is in domestic hot water storage tanks.
These valves will direct hot water from the boiler to various locations, such as radiators and the domestic hot water storage tank. But you also see them in zoned heating systems, such as hydronic gas heating or radiant floor gas heating.
How To Locate a Gas Shut-Off Valve In Any HVAC Appliance
The usual position of a gas shut-off valve on an HVAC system is along the gas pipe that leads into the unit. But in some cases, you need to know more about the position and focus on what the valve should look like. If you need to turn off the gas for safety or repairs, here's how you can find the gas shut-off valve:
Appearance
The valve usually looks like a small handle or lever. It may be red, yellow, or silver. It might look like a small wheel (an older style) or a straight lever (a newer style).
Lever Position
If the lever is in line with the pipe (same direction), it's ON. If the lever is turned sideways (across the pipe), it's OFF. To shut off the gas, turn the lever so it's across the pipe.
Sometimes, It’s behind Access Panels
If you can’t find the valve outside the unit, it might be behind a small access panel. Use a screwdriver to gently open it if needed (some just pop off).
QUICK TIP:
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Always make sure the unit is off and cool before touching anything inside.
If you still can’t find it, then go the old-fashioned way of starting where the gas pipe comes out of the wall. Follow it to the HVAC unit. The valve should be along the way.
How Do I Determine Which Valve Is Correct For My System?
Selecting the correct valve depends on multiple factors, including
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Application Type: Are you replacing a gas valve in a furnace, installing an expansion valve in an AC system, or controlling water flow in a boiler?
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Valve Size and Connection Type: Check the inlet and outlet size (e.g., 1/2" x 1/2") to ensure compatibility with your existing pipes or fittings.
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Fuel or Refrigerant Type: Some valves are specifically designed for use with natural gas, propane, R-410A refrigerant, or water.
Meanwhile, if selecting a solenoid or electric control valve, ensure the voltage (e.g., 24 V, 120 V) matches your system’s specifications. Also, HVAC valves have different BTU ratings or flow capacities. If you're uncertain, contact our team with your system details, and we’ll help you find the right valve.
Before You Go…
Now that you know the different types of gas shut-off valves for HVAC appliances and how to handle them safely, you may be at this juncture because of repairs and replacements.
At Snook & Aderton, we have decades of experience providing high-quality valves for HVAC systems.
Each valve is engineered to address specific system requirements, such as regulating gas flow in heating systems, controlling refrigerant in air conditioning units, or managing water flow in cooling applications. You can browse the various valves in our collection using the filter option to simplify your needs.