A high efficiency furnace main burner shuts off after initial ignition – There could be a few possible reasons why a high efficiency furnace’s main burner shuts off after initial ignition:

Flame sensor issue: The furnace’s flame sensor is responsible for detecting the presence of a flame. If it’s dirty or malfunctioning, it may not be able to detect the flame, causing the main burner to shut off. Cleaning or replacing the flame sensor may solve the problem.
Gas supply issue: If there’s an issue with the gas supply, the main burner may shut off after initial ignition. This could be due to a problem with the gas valve, low gas pressure, or a gas leak. A licensed HVAC technician should be called to diagnose and fix the issue.
Ignition system issue: If the ignition system is faulty, it may not be able to properly ignite the gas, causing the main burner to shut off. A licensed HVAC technician can inspect the ignition system and repair or replace any faulty components.
Overheating: If the furnace is overheating, it may automatically shut off the main burner as a safety precaution. This could be due to a dirty air filter, blocked vents, or a malfunctioning blower motor. Regular maintenance and cleaning can prevent overheating.
It’s important to have a licensed HVAC technician diagnose and fix any issues with a furnace to ensure safe and efficient operation.
Furnace main burner shuts off after ignition – If your furnace’s main burner shuts off immediately after ignition, there are several potential causes. Here are some common reasons why this might be happening:
Dirty or clogged burners: If the burners are dirty or clogged with debris, it can cause the flame sensor to shut off the burner immediately after ignition. Cleaning or replacing the burners may solve the issue.
Faulty flame sensor: The flame sensor is a safety feature that detects the presence of a flame. If it’s faulty or dirty, it may shut off the burner even though there is a flame present. Cleaning or replacing the flame sensor may solve the issue.
Low gas pressure: If the gas pressure is too low, it may cause the burner to shut off after ignition. This could be caused by a problem with the gas line or the regulator. A licensed technician should be called to diagnose and fix this issue.
Malfunctioning ignition system: If the furnace’s ignition system is not functioning properly, it may cause the burner to shut off after ignition. A technician should be called to diagnose and repair the issue.
Faulty thermostat: If the furnace’s thermostat is not functioning properly, it may cause the burner to shut off after ignition. Check the thermostat’s settings and ensure that it’s functioning properly. If it’s not, a technician may need to be called to diagnose and repair the issue.
It’s important to note that working with gas lines and furnaces can be dangerous. If you’re not comfortable diagnosing and fixing the issue yourself, it’s best to call a licensed technician to diagnose and repair the problem.
How long should furnace burners stay on – The length of time that furnace burners should stay on can vary depending on a number of factors, such as the size and type of furnace, the temperature setting, and the condition of the furnace and its components.
Generally speaking, a furnace burner should stay on long enough to heat the air in the furnace to the desired temperature and then shut off until the temperature drops below a certain point, at which point it will turn back on. This cycle of turning on and off is controlled by the furnace’s thermostat.
The exact length of time that the burners stay on will depend on the specific furnace and its settings, but a typical cycle may last anywhere from a few minutes to around 15-20 minutes. It’s important to note that if the burners are staying on for significantly longer periods of time, it could indicate a problem with the furnace and you may need to have it inspected by a qualified technician.
Furnace flame goes out after 5 minutes – There are several reasons why a furnace flame might go out after running for 5 minutes. Some possible causes include:
Dirty or clogged air filter: A dirty air filter can restrict the airflow to the furnace, causing it to overheat and shut down.
Malfunctioning thermostat: If the thermostat is not functioning properly, it may be turning off the furnace prematurely.
Faulty flame sensor: A faulty flame sensor can cause the furnace to shut off as it cannot detect the flame.
Damaged or dirty burners: Dirty or damaged burners can cause the flame to go out, as they cannot maintain a proper flame.
Gas supply issues: If there are issues with the gas supply, such as a faulty gas valve or a low gas pressure, it can cause the furnace flame to go out.
If you’re experiencing this issue, it’s recommended to have a professional HVAC technician inspect your furnace to determine the underlying cause and provide appropriate repairs.