Franchised Panel Builders Hand Book
Index
Chapter Content
PREFACE
2. TYPICAL ORGANIZATION & FACTORY LAYOUT
3. TENDERING
4. ORDER PROCESS, DESIGN & ENGINEERING
5. MATERIAL & PRODUCTION PLANNING
6. PRODUCTION
7. INSPECTION & QUALITY CONTROL
8. PACKING
9. SITE-TESTING & COMMISSIONING
10.USEFUL INFORMATION
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NEMA defines standards for various grades of electrical enclosures typically used in industrial applications. Each is rated to protect against designated environmental conditions. A typical NEMA enclosure might be rated to provide protection against environmental hazards such as water, dust, oil or coolant or atmospheres containing corrosive agents such as acetylene or gasoline. A full list of NEMA enclosure types is available from the NEMA website.
Below is a list of NEMA enclosure types; these types are further defined in NEMA ICS 6: Enclosures standard.
| NEMA Type | Definition |
| 1 | General-purpose. Protects against dust, light, and indirect splashing but is not dust-tight; primarily prevents contact with live parts; used indoors and under normal atmospheric conditions. |
| 2 | Drip-tight. Similar to Type 1 but with addition of drip shields; used where condensation may be severe (as in cooling and laundry rooms). |
| 3, 3S, 3X | Weather-resistant. Protects against weather hazards such as rain and sleet; used outdoors on ship docks, in construction work, and in tunnels and subways. 3X includes corrosions. |
| 3R | Intended for outdoor use. Provides a degree of protection against falling rain and ice formation. Meets rod entry, rain, external icing, and rust-resistance design tests. |
| 4 and 4X | Watertight (weatherproof). Must exclude at least 65 GPM of water from 1-in. nozzle delivered from a distance not less than 10 ft for 5 min. Used outdoors on ship docks, in dairies, and in breweries. The 4X model has corrosion resistance. |
| 5 | Dust-tight. Provided with gaskets or equivalent to exclude dust; used in steel mills and cement plants. |
| 6 and 6P | Submersible. Design depends on specified conditions of pressure and time; submersible in water or oil; used in quarries, mines, and manholes. |
| 7 | Hazardous. For indoor use in Class I, Groups A, B, C, and D environments as defined in the NEC. |
| 8 | Hazardous. For indoor and outdoor use in locations classified as Class I, Groups A, B, C, and D as defined in the NEC. |
| 9 | Hazardous. For indoor and outdoor use in locations classified as Class II, Groups E, F, or G as defined in the NEC. |
| 10 | MSHA. Meets the requirements of the Mine Safety and Health Administration, 30 CFR Part 18 (1978). |
| 11 | General-purpose. Protects against the corrosive effects of liquids and gases. Meets drip and corrosion-resistance tests. |
| 12 and 12K | General-purpose. Intended for indoor use, provides some protection against dust, falling dirt, and dripping noncorrosive liquids. Meets drip, dust, and rust resistance tests. |
| 13 | General-purpose. Primarily used to provide protection against dust, spraying of water and noncorrosive coolants. Meets oil exclusion and rust resistance design tests. |
NEMA enclosure ratings are similar to IEC IP Codes and can offer the same protections, but cannot directly be mapped.
Final Inspection and Testing
QCI Carry out ROUTINE TESTS as per IEC 60439-1 standards. The following minimum tests
must be performed:
Visual inspection test – Checking of the complete switchboard in accordance with IEC
60439-1 standards and approved drawings. Checking of Integrity of Wiring, Tightness of all
joints, and Torque test on all bus connections, etc.
Di-electric Test – Done using a MEGGER (verification of Insulation resistances between
phases, phase-neutral, phase-earth and neutral-earth). This test is also verified by a HIPOT
test using a 2.5kV test between phases for 1min.
Mass Continuity Test – To check if there is proper earth continuity from end of the
switchboard to the other. This test can be checked
Seismic effects on enclosures
In areas where seismic activity is possible, enclosures have to withstand
more influences and material-stress than in zones with no or a minimum
seismic risk. During an earthquake, sensitive electric/electronic equipment
can be subjected to motions that can over-stress equipment framework,
whereas the amount of motions and resulting stress depends on several
factors, like:
• Structural characteristics of the building
• Framework in which the equipment is contained
• Severity of the earthquake
Therefore, it is important to use enclosures that have been tested for
specific seismic zones.
Seismic certification
If compliance with the UBC-Zone certification is required, the requirements
for conformity are stated in GR-63-CORE ‘NEBS Requirements: Physical
Protection (NEBS or Network Equipment-Building System). This standard
identifies the minimum generic compatibility criteria for telecommunications
equipment, especially for:
• Earthquake and Office Vibration (Zone requirements)
• Fire resistance
• Thermal robustness
• Transportation and Handling
• Acoustic Noise
• Airborne Contaminates
The testing criteria of the GR-63-CORE are as follows:
• Door does not open during test.
• Equipment still operable immediately before and after test.
• Enclosure must be base mountable.
• Enclosure is bolted down to concentrate slab.
To test for physical performance, the GR-63-CORE contains some different
physical performance criteria and certification levels, such as:
• R4-44: All equipment shall be constructed to sustain the waveform
testing without permanent structural or mechanical damage.
• R4-45: Maximum single amplitude deflection at top of enclosure
relative to the base does not exceed 75mm (3”).
• R4-46: System should have a natural mechanical frequency greater
than 2.0Hz as determined by swept sine survey.
RITTAL
A residual-current device (RCD), or residual-current circuit breaker (RCCB) or residual twin-direct current couplet (R2D2), is an electrical wiring device that disconnects a circuit whenever it detects that the electric current is not balanced between the energized conductor and the return neutral conductor. Such an imbalance may indicate current leakage through the body of a person who is grounded and accidentally touching the energized part of the circuit. A lethal shock can result from these conditions. RCCBs are designed to disconnect quickly enough to prevent injury caused by such shocks. They are not intended to provide protection against overcurrent (overload) or short-circuit conditions.
Below is based on IEC 60364-5-54. This table provides two methods of determining the appropriate c.s.a. for both PE or PEN conductors.
| c.s.a. of phase | Minimum c.s.a. of | Minimum c.s.a. of | ||
| Cu AI | ||||
| Simplified | Sph≤ 16 | Sph(2) | Sph(3) | Sph(3) |
| 16 < Sph ≤ 25 | 16 | 16 | ||
| 25 < Sph ≤ 35 | 25 | |||
| 35 < Sph ≤ 50 | Sph/2 | Sph/2 | ||
| Sph > 50 | Sph/2 | |||
| Adiabatic method | Any size |
| ||
(1) Data valid if the prospective conductor is of the same material as the line conductor. Otherwise, a correction factor must be applied.
(2) When the PE conductor is separated from the circuit phase conductors, the following minimum values must be respected:
§ 2.5 mm2 if the PE is mechanically protected
§ 4 mm2 if the PE is not mechanically protected
(3) For mechanical reasons, a PEN conductor, shall have a cross-sectional area not less than 10 mm2 in copper or 16 mm2 in aluminium.
(4) Refer to table G53 for the application of this formula.
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