What is generally the consequence of operating a gas appliance with too much or too little excess air?

Operating a gas appliance with improper levels of excess air can greatly impact combustion efficiency and safety. When there is too much excess air, combustion may be incomplete, leading to a greater potential for the production of carbon monoxide and other harmful byproducts. This is because the fuel may not have enough time or adequate conditions to burn fully, especially if the gas is mixed with excessive amounts of air.

On the other hand, too little excess air can also create similar risks. Insufficient air can cause the fuel to burn inefficiently, resulting in unburned fuel gases lingering in the combustion chamber. This condition not only compromises the energy efficiency of the appliance but also contributes to the emission of pollutants and hazardous substances.

In summary, maintaining the correct balance of excess air is crucial for ensuring complete combustion, minimizing the risk of carbon monoxide production, and ensuring overall operational safety. Therefore, the consequence of operating with incorrect levels of excess air is primarily the increased risks of incomplete combustion.