CSLB C-10 Electrical ContractorEquipment and InstallationHard
A contractor installs conduit in a Class I, Division 1 hazardous location that terminates at an enclosure housing switches capable of arcing, sparking, or high temperatures. Per NEC 501.15, within what maximum distance from the enclosure must a sealing fitting be installed in this raceway?
- A36 inches
- B12 inches
- C18 inches
- D6 inches
Show answer & explanationAnswer & explanation
Correct answer: C. 18 inches
NEC 501.15(A)(1) requires a conduit seal to be located as close as practicable, and in no case more than 18 inches (457 mm), from an enclosure housing devices that may produce arcs, sparks, or elevated temperatures within a Class I, Division 1 location, to prevent the passage of gases and flame propagation through the raceway.
Why the other options are wrong
- A. 36 inches exceeds the code-permitted maximum distance.
- B. 12 inches understates the permitted maximum distance.
- D. 6 inches is more restrictive than the actual code-required maximum.
Class I Division 1 Seal Placement (501.15)
Sealing fittings in Class I, Division 1 locations must be installed within 18 inches of an enclosure containing arcing or sparking devices to prevent flame/gas propagation.
- 18 inches is the maximum allowed distance from the enclosure
- Seals prevent explosive gas migration through conduit
- Applies specifically to enclosures with switches, contacts, or similar arc-producing devices
Memory trick: 'Eighteen inches keeps the flame from finding a path.'