How To Ignite Furnace | do.thinkwell.com

Picture this: You’re snuggled up on the couch on a chilly evening, eager to warm your home with the comforting heat of your furnace. But wait! It’s not working. Panic sets in as you realize the prospect of freezing in your own home. Fear not, dear reader, for today, we embark on a journey to ignite your furnace, empowering you with the knowledge to conquer the cold and restore warmth to your abode.

First, let’s dispel any concerns and address the most common reasons why your furnace may not be igniting. One prevalent culprit is a lack of fuel. Check your fuel tank or gas line to ensure there’s ample supply. Next, verify that your furnace’s power is on and that the thermostat is set to “heat” mode. If your furnace has a pilot light, attempt to ignite it following the manufacturer’s instructions. However, if your furnace employs an electronic ignition system, proceed to the next troubleshooting step.

Now, let’s dive into the ignition process. Locate the furnace’s control panel and identify the ignition button. Press and hold the button for a few seconds until the igniter glows and the furnace attempts to light. If the furnace ignites successfully, congratulations! You’ve conquered the cold and restored warmth to your home. However, if the furnace fails to ignite, don’t despair. There may be an underlying issue that requires professional attention. In such cases, don’t hesitate to contact a qualified HVAC technician to diagnose and resolve the problem, ensuring your furnace operates optimally, keeping your home cozy and warm throughout the winter months.

Identifying the Furnace

The furnace is typically installed in a utility room, attic, or crawlspace. It is a large, metal box with a blower fan and a combustion chamber. The furnace is connected to the ductwork in your house, which distributes the heated air throughout the house.

There are a few different types of furnaces, but the most common type is a gas furnace. Gas furnaces burn natural gas or propane to create heat. Other types of furnaces include electric furnaces, which use electricity to create heat, and oil furnaces, which burn oil to create heat.

Locate the Furnace

The furnace is usually located in a basement, utility room, or attic. It is a large, metal box with a blower fan and a combustion chamber. The furnace is connected to the ductwork in your house, which distributes the heated air throughout the house.

Identify the Gas Line

The gas line to the furnace is usually made of black or yellow pipe. It will be connected to the furnace at the bottom or side of the unit. The gas line should have a valve that can be used to turn off the gas supply to the furnace.

Identify the Electrical Wiring

The electrical wiring to the furnace is usually black or red wire. It will be connected to the furnace at the top or side of the unit. The electrical wiring should have a circuit breaker that can be used to turn off the electricity to the furnace.

Furnace Type	Fuel Source
Gas furnace	Natural gas or propane
Electric furnace	Electricity
Oil furnace	Oil

Checking the Power Supply

Inspecting the Circuit Breaker or Fuse

Locate the electrical panel that powers your furnace and identify the circuit breaker or fuse that corresponds to the furnace. If the circuit breaker has tripped, reset it by flipping the switch back to the “on” position. If a fuse has blown, it will need to be replaced with one of the same amperage rating.

Testing the Voltage

To ensure that the furnace is getting sufficient power, use a voltage tester to check the voltage at the electrical terminals. The voltage should be within the range specified in the furnace’s manual. If the voltage is insufficient, there may be a problem with the wiring or a faulty transformer.

Checking for Ground Faults

Use a ground fault circuit interrupter (GFCI) tester to check for ground faults in the electrical panel. Ground faults can occur when an electrical current escapes from the intended path and flows through the ground. If a ground fault is detected, it is important to address the issue promptly to prevent electrical hazards.

Component	Check
Circuit Breaker or Fuse	Inspect for tripped breaker or blown fuse
Voltage	Test with a voltage tester to ensure sufficient voltage
Ground Fault	Use a GFCI tester to check for ground faults

Inspecting the Gas Supply

Before attempting to ignite the furnace, it is crucial to ensure that the gas supply is functioning properly. Follow these steps to inspect the gas supply:

Turn Off the Gas at the Main Valve

Locate the main gas valve, typically found near the gas meter. Turn the valve clockwise to shut off the gas supply.
Inspect the Gas Line

Visually inspect the gas line from the main valve to the furnace for any leaks, damage, or kinks. Look for signs of rust, corrosion, or loose connections.
Check the Gas Pressure

Using a manometer, connect it to the test port on the gas valve or near the furnace. Turn on the gas at the main valve and observe the manometer reading. The pressure should be within the range specified by the furnace manufacturer, typically between 7 inches of water column (w.c.) and 11 w.c.

If the gas pressure is too low or too high, or if you detect any leaks or damage, contact a qualified gas technician for further inspection and repairs.

Symptom	Possible Causes
No gas flow	Closed main gas valve, leak in gas line, clogged gas filter
Low gas pressure	Defective regulator, leak in gas line, undersized gas line
High gas pressure	Oversized gas line, malfunctioning regulator, improper gas valve adjustment

Troubleshooting the Thermostat

If your furnace isn’t igniting, one possible culprit is the thermostat. Here are a few steps you can take to troubleshoot the thermostat:

1. Check the batteries.

A dead or dying battery can prevent the thermostat from sending a signal to the furnace to ignite. Replace the batteries with new ones and see if that solves the problem.

2. Check the wiring.

Loose or disconnected wires can also prevent the thermostat from communicating with the furnace. Check the wiring connections at the thermostat and at the furnace, and make sure that they are all secure.

3. Check the thermostat settings.

Make sure that the thermostat is set to “heat” mode and that the desired temperature is set higher than the current room temperature. Some thermostats have a “fan only” setting, which will not turn on the furnace.

4. Check the thermostat’s display.

If the thermostat’s display is blank or shows an error message, it may be malfunctioning. Try resetting the thermostat by removing the batteries and then replacing them. If that doesn’t work, you may need to replace the thermostat.

Error Messages

Here are some common error messages that you may see on a thermostat display, along with their possible causes and solutions:

Error Message	Possible Cause	Solution
No power	Dead or dying batteries	Replace the batteries
Open circuit	Loose or disconnected wires	Check the wiring connections
Short circuit	Wiring error	Call a qualified electrician
Sensor error	Faulty temperature sensor	Replace the temperature sensor

Blowing Out the Furnace

Shut off the gas supply to the furnace completely. This is typically done by turning a valve located near the furnace. Once the gas is turned off, wait at least 5 minutes for any remaining gas to dissipate.

Locate the pilot light assembly on the furnace. This is usually a small metal tube with a flame burning at the end. Turn the pilot light knob to the “off” position.

Wait at least 30 minutes for the furnace to cool down completely. This will prevent any damage to the furnace when you blow out the pilot light.

Using a long, flexible lighter or a match, carefully reach into the pilot light assembly and blow out the flame. Be sure to blow gently so that you don’t damage the assembly.

Once the pilot light is out, wait at least 5 minutes before turning the gas supply back on. This will allow time for any residual gas to clear out of the furnace.


1.	Turn off the gas supply to the furnace.
2.	Locate the pilot light assembly on the furnace.
3.	Wait at least 30 minutes for the furnace to cool down completely.
4.	Blow out the pilot light.
5.	Wait at least 5 minutes before turning the gas supply back on.

Relighting the Pilot Light

If your furnace’s pilot light has gone out, you can relight it by following these steps:

1. Turn Off Gas Supply

Locate the gas valve on the furnace and turn it off. Wait 5 minutes for any residual gas to dissipate.

2. Open Furnace Door

Open the furnace door and locate the pilot light assembly. It is typically a small metal tube with a flame or spark igniter nearby.

3. Push Reset Button

There should be a reset button on the pilot light assembly. Press and hold it for 30 seconds to reset any safety features.

4. Ignite the Pilot

Use a long match or lighter to ignite the pilot light. Hold the flame to the base of the pilot tube for 30 seconds or until the flame stabilizes.

5. Release Reset Button

Once the pilot light is burning, release the reset button. It may take a few seconds for the flame to fully ignite.

6. Adjust Pilot Flame

The pilot flame should be a small, blue flame that is about 1/2 inch long. If the flame is too large or too small, adjust the gas valve knob next to the pilot assembly until the flame is the correct size.

Pilot Flame Size	Gas Valve Knob Adjustment
Too large	Turn clockwise to reduce gas flow
Too small	Turn counterclockwise to increase gas flow

Resetting the Furnace

If your furnace is not igniting, one of the first things you should try is resetting it. This can be done by following these steps:

Turn off the power to the furnace at the circuit breaker or fuse box.
Wait 30 seconds.
Turn the power back on.
Reset the furnace by pressing the reset button.
The reset button is usually located on the front or side of the furnace.
If the furnace does not ignite after resetting it, there may be a more serious problem.
You should call a qualified technician to diagnose and repair the problem.

Troubleshooting Furnace Ignition Problems
Check the thermostat to ensure it is set to “heat” and the desired temperature is set above the current room temperature.
Inspect the air filter and replace it if necessary. A dirty filter can restrict airflow and prevent the furnace from igniting.
Examine the flame sensor and clean it if it is dirty. A dirty flame sensor can prevent the furnace from detecting the presence of a flame and igniting.
Verify that the gas supply is turned on and that the gas pressure is within the recommended range.
Inspect the ignition system, including the ignition module, spark plug, and igniter. Replace any faulty components.
Check the limit switch and reset it if tripped. A tripped limit switch can prevent the furnace from starting.
If all else fails, consult a qualified HVAC technician for professional diagnosis and repair.

Calling for Professional Help

If you encounter persistent issues or safety concerns while troubleshooting your furnace, it is advisable to seek professional assistance from a qualified HVAC technician. This step is crucial to ensure the safety and effectiveness of your furnace system.

Here are some situations when calling a professional is recommended:

1. Gas Line Issues

If you suspect a gas leak or any issues related to the gas line, do not attempt to diagnose or repair it yourself. Contact a qualified gas technician immediately for safety reasons.

2. Electrical Faults

If you encounter electrical issues, such as sparking, unusual noises, or a burning smell, turn off the furnace and contact an electrician promptly. Electrical faults can be dangerous and should only be handled by a qualified professional.

3. Flame Problems

If the furnace flame is weak, flickering, or not igniting at all, it could indicate underlying issues. A technician can diagnose and resolve these problems.

4. Blower Malfunctions

A malfunctioning blower can prevent warm air from circulating through your home. A technician can assess and repair the blower to ensure proper airflow.

5. Thermostat Issues

If your thermostat is not functioning correctly, it can affect the furnace’s operation. A technician can diagnose and replace the thermostat as needed.

6. Pilot Light Problems

For furnaces with a pilot light, if the pilot light goes out or fails to ignite, a technician can safely relight or replace it.

7. Unusual Noises

Excessive or unusual noises coming from your furnace are often indicators of underlying issues. A technician can diagnose and address the source of these noises.

8. Multiple Failed Ignition Attempts

If your furnace repeatedly fails to ignite after several attempts, it could indicate significant problems. Contact a technician to thoroughly inspect and diagnose the furnace to prevent potential hazards or extensive damage.

Winterizing the Furnace

Winterizing your furnace is a crucial step to ensure its optimal performance during the cold winter months. Here’s a comprehensive guide on how to properly winterize your furnace:

1. Clean or Replace the Air Filter

A clean air filter allows for proper airflow and prevents dust and debris from accumulating within the furnace. Replace or clean the filter monthly during the winter.

2. Inspect the Heat Exchanger

The heat exchanger is the heart of the furnace, transferring heat from the combustion chamber to the air. Hire a qualified technician to inspect it for cracks or corrosion.

3. Check the Gas Line

Ensure the gas line is connected securely and free of any leaks. Use a soapy water solution to check for gas leaks. Bubbles indicate a leak, which requires immediate professional attention.

4. Inspect the Electrical Connections

Loose or corroded electrical connections can lead to malfunctions or even safety hazards. Check all wiring, terminals, and connectors for proper connections.

5. Clean the Blower Motor and Wheel

Dust and debris can accumulate on the blower motor and wheel, restricting airflow. Clean them thoroughly to ensure efficient operation.

6. Lubricate Moving Parts

Lubricate any moving parts, such as the motor bearings and blower fan, according to the manufacturer’s instructions. This reduces friction and prolongs the life of the furnace.

7. Check the Thermostat

Confirm that the thermostat is set to the desired temperature and is accurately controlling the furnace. Calibrate it if necessary.

8. Test the Furnace

Once you have completed all the above steps, turn on the furnace and test its operation. If any issues arise, consult a qualified technician.

9. Additional Winterization Tips for Different Furnace Types

Furnace Type	Additional Tips
Gas Furnace	Check the igniter and flame sensor for proper operation.
Electric Furnace	Inspect the heating elements and ensure they are heating evenly.
Oil Furnace	Clean the oil filter and check the oil level regularly.

Maintaining the Furnace

Regular maintenance is crucial for the optimal performance and longevity of your furnace. Here are ten essential maintenance tasks:

Replace Air Filter: Regularly change the furnace filter to prevent dust and debris from accumulating, which can restrict airflow and reduce efficiency.
Lubricate Moving Parts: Every two years, apply a few drops of oil to moving parts, such as motors and blowers, to ensure smooth operation.
Inspect Electrical Connections: Tighten any loose electrical connections to prevent arcing or electrical fires.
Check Flue Pipe: Ensure the flue pipe is in good condition and properly connected to the furnace to prevent toxic gases from entering the home.
Clean Condensate Drain: If your furnace has a condensate drain, clean it to prevent clogs that can cause water damage.
Inspect Burner Assembly: Inspect the burner assembly for any signs of corrosion or damage, and clean the burner ports to ensure proper gas flow.
Test Carbon Monoxide Detector: Regularly test your carbon monoxide detector to ensure it’s working properly and will alert you to potential gas leaks.
Calibrate Thermostat: Check the accuracy of your thermostat and calibrate it if necessary to ensure the furnace is operating at the desired temperature.
Read Owner’s Manual: Familiarize yourself with your furnace’s owner’s manual for specific maintenance instructions and troubleshooting tips.
Professional Maintenance: Schedule annual professional maintenance with a qualified technician to perform thorough inspections and cleanings, ensuring the furnace is operating safely and efficiently.

How to Ignite a Furnace

A furnace is a heating system that uses gas or oil to heat the air in a home. When the thermostat calls for heat, the furnace ignites and begins to blow warm air through the vents in the house. If your furnace is not igniting, there are a few things you can check to try to fix the problem.

First, check to make sure that the furnace is getting power. The power switch should be in the “on” position, and the circuit breaker or fuse should not be tripped. If the furnace is not getting power, you will need to call a qualified electrician to fix the problem.

If the furnace is getting power, the next step is to check the pilot light. The pilot light is a small flame that ignites the gas or oil in the furnace. If the pilot light is not lit, you can try to relight it by following the instructions in your furnace’s manual. If you are unable to relight the pilot light, you will need to call a qualified HVAC technician to fix the problem.

If the pilot light is lit, the next step is to check the gas or oil supply. Make sure that the gas valve is open and that there is enough oil in the tank. If the gas or oil supply is not adequate, you will need to call a qualified HVAC technician to fix the problem.