What is considered an Abnormal Operating Condition (AOC) before the appliance valve?

An Abnormal Operating Condition (AOC) refers to any situation that deviates from the standard operational parameters and poses a risk during the operation of gas appliances. In this case, having a union before the appliance valve is deemed an AOC because it can introduce potential leak points or improper connections that could compromise the safe functioning of the gas line. Unions, while useful for making gas lines easier to disconnect and service, are not considered a standard practice within the proximity of an appliance valve according to safety guidelines.

Proper installation of all connections, missing venting, and standard operational methods do not illustrate abnormal conditions since they either pertain to best practices or acceptable installation techniques. For instance, missing venting can lead to unsafe gas buildup, but within the context of the question, it does not pose an operational issue directly with the connection before the appliance valve. Understanding what constitutes an AOC is essential for maintaining safety and compliance in gas piping systems.