How far downstream of a fuel burning duct heater must duct linings be removed?

When dealing with fuel-burning duct systems, proper safety and code compliance are paramount to prevent hazardous situations such as combustion gas accumulation or fire hazards. The requirement to remove duct linings is specifically related to ensuring that these systems operate safely and efficiently by maintaining a clear and unobstructed flow of combustion gases.

In the context of duct heaters, the North Carolina Mechanical Code specifies that duct linings must be removed a minimum of 6 inches downstream of a fuel-burning duct heater. This distance ensures that any heat, combustion gases, or byproducts generated by the heater do not interact with the lining material, which could potentially lead to overheating, degradation of the lining, or a reduction in the system's overall efficiency. Furthermore, maintaining this clearance helps to ensure that the airflow remains effective, reducing the likelihood of the heater impacting or being impacted by any material that could catch fire or degrade due to high temperatures.

Understanding this requirement reinforces the importance of adhering to manufacturer specifications and local codes to maintain both safety and operational efficiency in HVAC systems.