The North American Explosion proof Certification System (NEC system) has significant differences from China's national standard system supported Explosion proof Certification System (GB system) in terms of classification and grouping of explosive substances, classification of hazardous areas, explosion protection methods, installation and wiring. Although the Electrical Installation Regulations (NEC) in the United States have gradually accepted the hazardous area zoning system of the IEC60079 series standards (corresponding to China's national standard GB/T 3836 series standards) since the 1996 edition, and the product standards in the United States have also been revised and supplemented accordingly. However, manufacturers of explosion-proof electrical products familiar with China's explosion-proof certification system and users in industries such as petrochemicals who widely use imported products still feel confused about the classification system in North America and the design and manufacturing requirements, installation and use, and reasonable selection of explosion-proof electrical products under China's explosion-proof certification system. Especially for manufacturers who are striving to enter the North American market, they are eager to understand the differences between the two standard systems on how to smoothly enter the North American market.
1、 Differences in venue division

1Classification and grouping differences of explosive substances

2Differences in zoning of explosive sites

3Differences in temperature groups

2、 Differences in Protection Methods

Protection methods and scope of application for North American NEC system and Chinese GB system

1. Explosion proof type

2. Intrinsic safety type

In the NEC system, the intrinsic safety type corresponds to the intrinsic safety type IA in the GB system.

In the NEC system, there is no intrinsic safety type IB; In the GB system, it is also limited to use in Zone 1.

In terms of structural requirements, it is equivalent to the "non inductive circuits" and "non inductive components" in the NEC system.

3. Increased safety type: In the NEC system, there is no such protection method.

4. Non sparking type: In the NEC system, there is no such protection method.

5. Sealed type: In the NEC system, this method is only used for local protection or component protection.

6. Special type: In the NEC system, there is no such protection method.
3、 Differences in installation methods

4、 Comparison of two major system symbols

NEC system: Class I, Division 1,Group C,T6

GB/IEC system: Ex db IIB T4 Gb

5、 Comparison of two major system standards

China/IEC Explosion proof System: GB/T 3836 and IEC60079 series standards

NEC Explosion proof System: UL Standard

Explanation: The explosion-proof product standards in the North American standard system are divided by specific types of products, such as ANSI/UL894 (switches for hazardous locations), while the GB standard system is divided by explosion-proof types The explosion-proof product standards in the NEC system specify both the requirements for explosion-proof structures and the performance requirements for products related to explosion-proof safety

6、 Comparison between NEMA enclosure type rating and IP protection rating

NEMA: National Electrical Manufacturers Association of the United States