What is a Furnace Smart Valve and When Should You Replace It

furnace smart valve“What is a furnace smart valve or how does it work?” If you are asking these or related questions you probably are experiencing some problems with your furnace, heating unit or boiler, or maybe you are simply curious to learn more. Truth is that though seeming like a simple or basic device, this little piece plays a key role in the operation of your heating appliances that are gas-fired for instance residential boilers, central furnaces and other types. Usually, the smart valve is the cause of most problems and knowing how to detect a problem and possibly replacing the faulty unit goes a long way in enjoying good service from the gas-fired heating appliance. Furthermore, it saves you the trouble of misdiagnosing and replacing the wrong part.

What is a Furnace Smart Valve?


The Smart Valve is a critical part of any gas-fired furnace and will be found in residential boilers, central furnaces, commercial heaters, cooking appliance and more. It is a silver-colored unit that is located near the hot surface igniter that produces the pilot flame which later on turns on the main flame. Its role is to control the gas ignition system by first sensing the little gas that is needed to ignite the pilot flame then later on triggers the gas than ignites the main flame. In order to function properly, it needs to be accurate and sense everything as recommended by the manufacturer failure to which may lead to erratic operation or no ignition. Nonetheless, just like any other product, it will fail over time due to wear & tear, accident or poor handling.

How Does It Work

The furnace smart valve works in a sequential manner to control how the flame in a gas furnace turns on in a cycle. It is designed to first sense the gas needed for the pilot flame and once it’s on it then triggers the lighting of the main flame. Everything works electronically and it’s important for the electrical connections and circuitry to be in good order. The pilot flame is triggered when the hot surface igniter is heated up electronically and then sparks the gas flame. The valve then triggers the flow of gas in the main vents and ignites the main flame and this sequence takes place in every cycle. Both pilot and main gas operate as a unit and need to be fairly-accurate for maximum efficiency.

Common Problems

Over time, the smart valve will become less efficient as it ages or may suddenly stop functioning due to a fault. It helps to have an idea of the common symptoms associated with a failing or faulty furnace smart valve:

1. Pilot doesn’t come on: This may be caused by lack of current or voltage at the unit. A millimeter or voltmeter helps to ascertain whether the correct voltage is reaching the valve.

2. Pilot comes on but Main gas doesn’t: This is most-likely caused by a failing unit that is able to sense the pilot flame but not the main flame. The next likely cause of action is replacing the entire unit.

3. No Pilot Flame: This may be caused by a bad hot surface igniter that fails to light up even after the valve triggers the pilot gas. A physical inspection may reveal a worn-out or broken igniter (a small rod that turns red-hot when activated).

4. No clicking Sound: When the hot surface igniter is activated a clicking sound is activated. However, when the gas furnace or boiler doesn’t come on and the sound isn’t heard, it’s most likely a faulty smart valve.

When to Replace a Furnace Smart Valve

The above instances will require the furnace smart valve to be replaced except when you ascertain it’s a faulty electrical connection. You will need to rely on tools such as a voltmeter/multi-meter, screwdriver, pliers, your eyes and ears to diagnose the problem. Always replace the faulty unit with the same type and ensure it is genuine. You need to be careful not to touch the hot surface igniter as it can easily break. Furthermore, make sure the unit is turned off before attempting any repairs. It is also advisable to confirm that related accessories such as transformer, vent damper, thermostat, switches, wiring are in good shape.

Are you still asking “what is a furnace smart valve or how does it work?” The above article should have answered this question and when in doubt always seek guidance from reputable and experienced HVAC experts.