A pilot light stays on to serve as a constant, reliable ignition source for your gas appliances. Whenever you turn on the heat, hot water, or a burner, the pilot light instantly ignites the main flow of gas, ensuring it burns safely without building up in your home.
The pilot light on a gas furnace is a small flame that ignites the burner inside the unit. The purpose of the pilot light is to provide a continuous source of ignition for the burner so that the furnace can heat the home. Most furnaces have an electronic ignition, which means that the pilot light is unnecessary.
During periods when you aren't using your fireplace or stove, you have no actual need to run the pilot light. Doing so will waste a small amount of energy, and many homeowners wish to keep energy waste to a minimum. As little as pilot lights are, they're still real flames and create a small amount of real heat.
Furnaces should cycle 3-8 times per hour. Short cycles may indicate oversized units or airflow issues. Long cycles can signal undersized furnaces or insulation problems. Regular maintenance helps ensure proper cycling and performance.
In many systems, a broken pilot light will prevent the appliance from working at all. This is a safety precaution to prevent a buildup of excess gas in the unit, which can be dangerous for you and your family, potentially leading to a gas leak.
How long does it take to air out a house after a gas burner is left on? Usually, when you can no longer smell gas, or around 30 minutes to two hours, it's safe to walk back in.
A brief whiff of gas when relighting a pilot light is normal. What's not normal is when that smell lingers, spreads, or gets stronger.
In moderate weather, 2-3 cycles per hour is normal. During very cold weather, up to 6 cycles per hour might be normal. If your furnace is cycling more frequently than this, it's likely short cycling.
5 Warning Signs It's Time for Furnace Replacement
A typical furnace runs for approximately 10 to 15 minutes per cycle, cycling three to eight times per hour. A short cycling system runs for less than five minutes, then quickly restarts, often cycling much more frequently. This pattern prevents efficient heating and creates massive strain on your equipment.
Your boiler pilot light is a very important part of your boiler. The pilot light or flame needs to be lit all the time to make sure that your boiler can produce hot water for your taps and central heating as and when it is needed.
The little flame you see in your gas fireplace after you have turned it off is called a pilot light. A Standing Pilot Light runs constantly, whether your fireplace is on or off.
A bad furnace thermocouple often causes the pilot light to go out repeatedly or prevents the furnace from staying on at all. Common warning signs include a furnace that won't ignite, a pilot light that won't stay lit, frequent shutdowns, or no heat even though the thermostat is calling for warmth.
Gas stoves can also release carbon monoxide — a poisonous, odorless gas that can cause health issues ranging from headaches to confusion, loss of consciousness and death. The risk is higher if the stove is installed incorrectly or not vented properly. Gas stoves can even release pollution when they're not being used.
6 Common Reasons Your Pilot Light Keeps Going Out
Short cycling
This is one of the most common furnace problems, and it can stress important furnace components such as the blower motor, limit switch, or flame sensor. There are several potential causes of short cycling, including some that are related to your furnace's built-in safety systems.
The Average Furnace Lifespan
A well-maintained furnace can last at least 15 to 20 years, but completing annual maintenance and being diligent with furnace repairs can extend its life even longer.
Scraping Sounds
Ask an expert, “What does a failing furnace sound like?” and they'll tell you to pay attention to any scraping or grinding noises. This distinct sound might indicate loose parts or issues with your blower motor.
Typically, a properly sized furnace will run for about 10–15 minutes per cycle during colder months. If your furnace turns on every few minutes, it may be short cycling, which can indicate issues such as a clogged filter, blocked vents, or an oversized unit.
The heat exchanger is often considered the most costly part of a furnace to repair or replace. It is a critical component that transfers heat from the combustion process to the air that circulates throughout your home. Over time, heat exchangers can crack due to the constant heating and cooling cycles they undergo.
For most customers, we recommend turning on your furnace when the weather is consistently below 18° Celsius, which usually happens to be around the end of September, or early October. Some homeowners try to put off turning on their furnace as long as they can to save money, which is okay if you're healthy adults.
If you smell a sulfur or rotten-egg-like odor, you could have a gas leak. Natural gas is naturally colorless and odorless. We add an odorant called mercaptan to natural gas, which gives it a distinctive smell. In some cases, you can also identify natural gas by sight or sound.
Hydrogen sulfide, which is very common, produces a rotten egg smell. Methanethiol produces a smell similar to rotting vegetables or garlic. Dimethyl sulfide is often described as smelling like cabbage but might add a sweetness to the overall smell of gas.
Pilot lights can be a source of carbon monoxide because the by-products of combustion are released inside the home rather than vented to the outside. Gas ovens and ranges should be monitored closely and kept in good working order.