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 ELECTRICAL STANDARDS
Director's Orders (DOs)
Building Codes
- NFPA Codes and Standards, but not NFPA 5000
- NESC National Electrical Safety Code
- NEC 2008
Directives, Standards, and NPS Guidelines
- IEEE - Standards
- EIA/TIA Standards 568 & 569
- IESNA Illuminating Engineers Society of North America
Professional Guidance
Load Requirements:
- NEC 2008
- Nameplate/Manufacturers Data
- 25% minimum spare capacity typical for future expansion
Utilities:
- Coordinate with utility companies as early as possible
- Underground distribution as much as possible
- NPS prefers not to own & operate utilities
- TVSS Protection on all Service Entrances
Telecommunication:
- EIA/TIA Standards, see above
- Cat 6 Cabling - (2) per 3/4" conduit; (1) Data, (1) Voice per each voice / data outlet (typical)
- Telephone Service Entrance (Demarcation Point) - Meet Local Phone Company Requirements
Conduit:
- Site specific, in general Schedule 40 PVC for underground
- Minimum branch circuit conduit size = 3/4"
- Provide conduit for all wiring (minimum size 3/4")
- See table below
Power Wiring:
- THWN / THHN
- Underground - THWN / XHHW
- No MC or AC type cabling in walls in new construction
- No surface mounted MC or AC type cabling where rigid raceway can be used
- Copper conductors
- Copper Buswork
Overcurrent Protection:
- Fully rated - Series rated is not desired
- Breakers preferred for reset capability
(sizes 15 amperes or greater)
- Fuse selection shall comply with NEC requirements and equipment manufacturers recommendations.
Equipment and Materials:
- Listed and labeled as defined in NEC Article 100
for application
- Conduit - see table below for environment and use
ENVIRONMENT |
RACEWAY |
BOXES, ENCLOSURES,
CABINETS |
Dry locations, concealed |
RMC, IMC, EMT, RNC, ENT1, FMC, LFMC, LFNC, WW |
SM, FS/FD, NM, NEMA 1 |
Exposed, subject to damage |
RMC, IMC |
SM, FS/FD, NM, NEMA 1 |
Exposed, not subject to damage |
RMC, IMC, EMT, RNC, ENT2, FMC, LFMC, LFNC |
SM, FS/FD, NM, NEMA 1 |
Wet locations, subject to damage |
RMC3, IMC3, EMT3, WW7 |
FS/FD, NEMA 4, 4X |
Wet locations, not subject to damage |
RMC3, IMC3, EMT3, RNC, ENT2, LFMC, LFNC, WW7 |
FS/FD, NM,
NEMA 4, 4X |
Outdoor locations, exposed to rain, sleet, wind-blown dust, and external icing |
RMC3, IMC3, EMT3, LFNC, WW7 |
FS/FD, NEMA 3,
3R, 3S |
Submerged |
RMC3, IMC3, RNC |
NEMA 6, 6P |
Embedded in concrete |
RMC, IMC, EMT4, RNC, ENT4 |
FS/FD |
Under concrete slab |
RMC, IMC, EMT4 |
|
Underground, direct burial |
RMC3, IMC3, EMT3, RNC, ENT, LFNC |
|
Embedded burial |
RMC, IMC, EMT4, RNC, ENT4, LFNC |
|
Industrial location, general |
RMC, IMC, EMT, RNC, FMC, LFMC, WW |
FS/FD, SM,
NEMA 12, 12K |
Subject to corrosion |
RMC3, IMC3, EMT3, RNC, LFMC |
NEMA 4X, 11 |
Subject to oil, vapors |
RMC, IMC, LFMC |
FS/FD, NEMA 13 |
Hazardous Class I, Division 18 |
RMC, IMC, FMC8 |
NEMA 7, 8 |
Hazardous Class I, Division 28 |
RMC, IMC, LFMC, FMC, WW5 |
FS/FD, NEMA 1, 7, 8, 12 |
Hazardous Class II, Division 18 |
RMC, IMC, LFMC, WW5 |
NEMA 9 |
Hazardous Class II, Division 28 |
RMC, IMC, LFMC, WW5 |
FS/FD, NEMA 1, 9, 12 |
Hazardous Class III8 |
RMC, IMC, LFMC, WW5 |
FS/FD, NEMA 12 |
TABLE LEGEND |
TABLE NOTES |
RMC - Rigid metal conduit
IMC - Intermediate metal conduit
EMT - Electrical metallic tubing
FMC - Flexible metal conduit
LFMC - Liquidtight flexible metal conduit
RNC - Rigid nonmetallic conduit
ENT - Electrical nonmetallic tubing
LFNC - Liquidtight flexible metal conduit
WW - Wireway
SM - Sheet metal box
FS/FD- Cast metal box
NM - Nonmetallic
NEMA - Re: NEMA 250 type classification |
1 — Finishes must provide barrier with 15-minute rating.
2 — Building not more than 3 stories above grade.
3 — Corrosion protection required.
4 — With fittings for purpose.
5 — Enclosed and gasketed.
6 — Dusttight wireway only.
7 — Raintight wireway only.
8 — Suitable for hazardous location. |
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