When is it against EPA regulations to use system-dependent recovery equipment?

Using system-dependent recovery equipment becomes a violation of EPA regulations when the appliance contains over 15 pounds of refrigerant. This rule is in place because system-dependent recovery units rely on the system's operational efficiency to recover refrigerant, which can pose risks of releasing refrigerants into the environment when the system is larger and contains a significant amount of refrigerant.

In systems containing over 15 pounds of refrigerant, more robust recovery methods are mandated to ensure safe and complete refrigerant recovery. The larger amount of refrigerant means that any residual left in the system during inadequate recovery could lead to greater potential environmental harm, making the use of a more efficient recovery method necessary for compliance with EPA regulations.

The other answer choices do not represent conditions that are directly tied to EPA regulations regarding the use of system-dependent recovery equipment. For instance, the age of the appliance or its operational status do not inherently determine the appropriateness of this type of recovery equipment; rather, it is specifically the amount of refrigerant that governs the regulations.