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Electrical Equipment Enclosure Types

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Electrical Equipment Enclosure Types

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NEC Article 110.28

Enclosures (other than surrounding fences or walls) of switchboards,

panelboards, industrial control panels, motor control centers, meter sockets,

enclosed switches, transfer switches, power outlets, circuit breakers,

adjustable-speed drive systems, pullout switches, portable power

distribution equipment, termination boxes, general-purpose transformers,

fire pump controllers, fire pump motors, and motor controllers, rated not

over 600 volts nominal and intended for such locations, shall be marked with

an enclosure-type number as shown in Table 110.28.

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Outline

• Hazardous Location Classes

• Hazardous Location Groups

• Hazardous Location Divisions

• Enclosure Types

• Non-Hazardous Locations

• Hazardous Locations

• Enclosure Examples

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Electrical Equipment Enclosure Types

• Class 1• Presence of flammable gas or vapors• Potential for explosion• Includes: petroleum refineries, aircraft hangers, dry cleaning plants

• Class 2• Presence of combustible dust• Potential for explosion• Includes: grain elevators, flour/feed mills, spice grinding plants

• Class 3• Presence of easily-ignitable fibers• Potential for ignition of fibers• Includes: textile mills, flax processing plants, any plant creating sawdust

Hazardous Location Classes

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Electrical Equipment Enclosure Types

• Class 1• Group A: Acetylene• Group B: Hydrogen, etc.• Group C: Hydrocarbons, fuels, solvents, etc.

• Class 2• Group E: Metal dusts (conductive & explosive)• Group F: Carbon dusts (all explosive, some conductive)• Group G: Flour, starch, grain, combustible plastic, chemical dust (explosive)

• Class 3• Textiles, woodworking, etc. (easily ignitable, not likely explosive)

Hazardous Location Groups

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Electrical Equipment Enclosure Types

• Division 1 – Normal Conditions• Ignitable concentrations of hazards exist under normal operation• Ignition of hazard is caused by frequent maintenance, repair work, or

equipment failure• Division 2 – Abnormal Conditions• Ignitable concentrations of hazards are handled, process, or used• These hazards are normally in closed containers or systems• Hazards can only escape through accidental rupture or breakdown of their

containers or systems

Hazardous Location Divisions

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Electrical Equipment Enclosure Types

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Non-Hazardous Location Enclosures

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Electrical Equipment Enclosure Types

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Electrical Equipment Enclosure Types

• #R = Protection against falling dirt only - not windblown dust• #X = Protection against corrosion• #S = Protection against sleet – able to operate when covered in ice• #K = Constructed with knockouts• #P = Protection against corrosion and prolonged submersion

Enclosure Letter Designations

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Electrical Equipment Enclosure Types

• Type 7: Constructed for indoor use in hazardous locations classified as Class 1, Division 1, Group A, B, C, or D as defined in NFPA 70.

• Type 8: Constructed for indoor/outdoor use in hazardous locations classified as Class 1, Division 1, Groups A, B, C, or D as defined in NFPA 70.

• Type 9: Constructed for indoor use in hazardous locations classified as Class 2, Division 1, Groups E, F, or G as defined in NFPA 70.

• Type 10: Constructed to meet the requirements of the Mine Safety and Health Administration, 30 CFR, Part 18 (use in mines with atmospheres

containing methane or natural gas, with or without coal dust).

Hazardous Location Enclosures

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Electrical Equipment Enclosure Types

NEMA 1 Enclosure

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• Indoor use• Protects against:

1. Incidental contact with enclosed equipment2. Falling dirt

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Electrical Equipment Enclosure Types

NEMA 3R Enclosure

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• Outdoor use• Protects against:

1. Incidental contact with enclosed equipment

2. Rain, snow, sleet

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Electrical Equipment Enclosure Types

NEMA 4X Enclosure

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• Indoor use• Protects against:

1. Incidental contact with enclosed equipment

2. Falling dirt3. Falling liquids and light splashing4. Circulating dust, lint, fibers5. Settling dust, lint, fibers6. Corrosive agents

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Electrical Equipment Enclosure Types

NEMA 6P Enclosure

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• Indoor use• Protects against:

1. Incidental contact with enclosed equipment

2. Falling dirt3. Falling liquids and light splashing4. Circulating dust, lint, fibers5. Settling dust, lint, fibers6. Corrosive agents7. Occasional prolonged

submersion

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Electrical Equipment Enclosure Types

NEMA 7 Enclosure

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• Indoor use• Use in areas classified as Class 1,

Division 1, Groups A, B, C, D• Designed to contain an internal

explosion without causing external hazard

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Electrical Equipment Enclosure Types

NEMA 12 Enclosure

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• Indoor use• Constructed without knockouts• Protects against:

1. Falling dirt2. Circulating dust, lint, fibers3. Dripping/splashing water

Electrical Equipment Enclosure TypesCONCLUSION

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