How many inches must vented wall furnaces be located from a door to prevent interference?

Vented wall furnaces must be installed at a minimum distance of 12 inches from a door to ensure proper airflow and prevent any interference with the door's operation. This distance is crucial because it allows the door to open and close freely without obstructing the furnace or being affected by heat or exhaust emitted from the unit. The 12-inch requirement is typically based on safety standards and is designed to minimize risks associated with combustion gases and to maintain efficiency in the operation of the heater. Ensuring that the furnace is adequately distanced from doors also helps in compliance with local building codes, which are intended to protect both property and personal safety.