04.05 Does the electrical work need to be explosion-proof?

Diesel fuel commonly used for generators is #2 Diesel which has a flash point of about 120 degrees F. This would classify diesel fuel in NFPA standards as a combustible and not a flammable liquid. Explosion proof electrical construction is required for flammable liquids, but not typically combustible liquids. So fuel rooms in buildings are typically ordinary electrical aras and not explosion proof.

However, local fire codes – or the facility insurance requirements, may specify that the fuel storage room is a hazardous electrical area. This classification may be either Class 1 / Division 1 meaning the conditions for fire / explosion are always present, or Class 1 / Division 2 meaning the conditions are present under upset conditions.

Class 1 / Division 2 Construction can be accomplished by (a) control panels and devices to be constructed of all C1D2 approved components, (b) explosion proof motors, (c) all contactors and spark potential devices located within NEMA 7 explosion proof enclosures, (d) control panels and devices to be constructed of all C1D2 approved components, (e) intrinsically safe or explosion-proof instrumentation and sensors, (f) rigid steel conduit with seals at the area boundaries.

Class 1 / Division 1 Construction would not allow item (a) above. Control panels would need to be in explosion-proof enclosures – or more commonly, located outside of the room in an ordinary electrical area.

Lighting, utility outlets, and other electrical devices in the rooms also need to be addressed for the hazardous electrical environment.