Suspended-type unit heaters shall be installed with clearances to combustible materials of not less than _____ inches at the sides, _____ inches at the bottom, and _____ inches above the top where the unit heater has an internal draft hood.

The correct clearances for suspended-type unit heaters with an internal draft hood are 18 inches at the sides, 12 inches at the bottom, and 6 inches above the top. These specified clearances are crucial for ensuring safety and preventing any fire hazards associated with heating equipment. The side clearance helps to accommodate airflow and prevent overheating of surrounding structures. The bottom clearance is designed to ensure that the unit can operate without obstruction and allows for proper heat dispersion. The clearance above the top is equally important, as it prevents any potential for heat build-up that could ignite combustible materials placed too close to the unit.

Adhering to these clearance requirements is in line with established safety standards and building codes, which are enforced to promote safe and effective heating practices in various applications. Other choices do not meet these safety standards, which can lead to risks associated with improper installation.