If a furnace makes a loud bang upon ignition, what is the first action a technician should take regarding the gas pressure?

When a furnace makes a loud bang upon ignition, this often indicates a problem with the ignition process, which can lead to delayed ignition. The first action a technician should take is to check the supply gas pressure. Proper gas pressure is crucial for ensuring that the gas-air mixture is correct for combustion. If the pressure is too low, it may result in insufficient gas reaching the burners, potentially causing a delay in ignition, which can lead to the loud bang as the gas ignites all at once.

By checking the supply gas pressure first, the technician can determine whether the gas is being delivered at the correct pressure for safe and efficient combustion. If the gas pressure is not within the manufacturer's specifications, adjustments can be made or further investigation into the cause of the low pressure can occur. Ensuring proper gas supply is fundamental to diagnosing and resolving the issue effectively.