What is the required clearance above a warm air plenum without a 200 degree lint switch?

In the context of HVAC systems, the clearance above a warm air plenum is crucial for ensuring safety and preventing overheating. If a warm air plenum does not have a 200-degree lint switch, which is a safety mechanism that can shut off the heater in case of excessive temperature, the required clearance needs to be sufficient to prevent any potential heat buildup that could lead to a fire hazard. A clearance of 2 inches is mandated in this situation to provide enough space for proper airflow, minimize heat transfer to nearby combustibles, and allow for maintenance and servicing.

This requirement is established within building codes and standards to ensure the safe operation of heating systems. Adequate clearance not only helps in maintaining optimal functioning but also complies with safety regulations that protect both the structure and its occupants from fire risks. The specific clearance of 2 inches, in particular, strikes a balance between performance and safety, making it the correct answer in this scenario.