# Lighting Calculations Class 101

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```					Basic Electrical Design
NEC Code Applications
Class 101

Jim Fuller
4/9/08
Two basic principles
• Harmonic overheat transformers
• Overheating motors
• Overheating wire and circuit breaker
• Energy is conserve: Law of Conservation
• Transformer: Input = Output + losses
• Motor: input = output + losses
Objective
•   Electrical Codes
•   Enclosures
•   Basic Electrical Formulas
•   Conduit Sizing
•   Cable Ampacity Table NEC 310-16
•   Conductor Sizing
•   Sizing Transformer CB, Cable and Conduit
•   Transformer Formula
•   Ground Wire Sizing
•   Sizing Conductor and OCPD for 480V Motors
•   Rule of Thumb
Electrical Codes
•   NFPA 70 = NEC (national Electrical code)
(sizing wire, conduit, transformer, safety and etc.)

•   NFPA (National Fire Protection Assoc.)
(example NFPA 101 – life safety fire alarm, egress and etc..)

•   UL = national laboratory
(testing lab for quality of equipment)

•   NEMA – National Electrical Manuf Assoc.
(Quality of equipment, size i.e. MG-1 for motors

•   IEEE
(Manuf criteria, example BIL level, short circuit rating)
Nema type Enclosures
NON-CLASSIFIED LOCATION ENCLOSURESNEMA enclosures 2, 5, 12, 12K and 13 are not intended to provide protection against conditions such as
internal condensation. NEMA enclosures 3, 3R, 38, 4, 4X, 6 and 6P are not intended to provide protection against conditions such as internal condensation or
internal icing.
•   Type 4X Enclosures
•        Type 1 Enclosures                                                                  •   Type 4X enclosures are intended for indoor or outdoor use primarily to
•        Type 1 enclosures are intended for indoor use primarily to provide a degree            provide a degree of protection against corrosion, windblown dust and rain,
of protection against limited amounts of falling dirt in locations where unusual       splashing water, and hose-directed water; and to be undamaged by the
service conditions do not exist.                                                       formation of ice on the enclosure.
•        Type 2 Enclosures                                                                  •   Type 5 Enclosures
•        Type 2 enclosures are intended for indoor use primarily to provide a degree        •   Type 5 enclosures are intended for indoor use primarily to provide a degree
of protection against limited amounts of falling water and dirt.                       of protection against settling airborne dust, falling dirt, and dripping
•        Type 3 Enclosures                                                                      noncorrosive
•        Type 3 enclosures are intended for outdoor use primarily to provide a degree       •   Type 6 Enclosures
of protection against rain, sleet, and wind-blown dust; and to be undamaged        •   Type 6 enclosures are intended for indoor or outdoor use primarily to provide
by the formation of ice on the enclosure.                                              a degree of protection against hose-directed water and the entry or water
•        Type 3R Enclosures                                                                     during temporary submersion at a limited depth; and to be undamaged by the
•        Type 3R enclosures are intended for outdoor use primarily to provide a                 formation of ice on the enclosure.
degree of protection against rain and sleet; and to be undamaged by the            •   Type 6P Enclosures
formation of ice on the enclosure. They must have a provision for a drain          •   Type 6P enclosures are intended for indoor or outdoor use primarily to
hole.                                                                                  provide a degree of protection against hose-directed water and the entry of
•        Type 3S Enclosures                                                                     water during prolonged submersion at a limited depth; and to be undamaged
•        Type 38 enclosures are intended for outdoor use primarily to provide a                 by the formation of ice on the enclosure.
degree of protection against rain, sleet, and wind- blown dust, and to provide     •   Type 12 Enclosures
for operation of external mechanisms when ice laden.                               •   Type 12 enclosures are intended for indoor use primarily to provide a degree
•        Type 4 Enclosures                                                                      of protection against circulating dust, falling dirt, and dripping noncorrosive
•        Type 4 enclosures are intended for indoor or outdoor use primarily to provide          liquids.
a degree of protection against windblown dust and rain, splashing water, and       •   Type 12K Enclosures
hose-directed water; and to be undamaged by the formation of ice on the            •   Type 12K enclosures are intended for indoor use primarily to provide a
enclosure.                                                                             degree of protection against circulating dust, falling dirt, and dripping
•        Type 4X Enclosures                                                                     noncorrosive liquids. The knockouts shall be provided only in the top or
•        Type 4X enclosures are intended for indoor or outdoor use primarily to                 bottom walls, or both.
provide a degree of protection against corrosion, windblown dust and rain,         •   Type 13 Enclosures
splashing water, and hose-directed water; and to be undamaged by the               •   Type 13 enclosures are intended for indoor use primarily to provide a degree
formation of ice on the enclosure.                                                     of protection against lint, dust, spraying of water, oil, and noncorrosive
•        Type 5 Enclosures                                                                      coolant.
•        Type 5 enclosures are intended for indoor use primarily to provide a degree        •   CLASSIFIED LOCATION ENCLOSURES
of protection against settling airborne dust, falling dirt, and dripping           •   Type 7 Enclosures
noncorrosive                                                                       •   Type 7 enclosures are for indoor use in locations classified as Class I,
•                                                                                               Groups A, B, C, or D, as defined in the National Electrical Code.
•        Type 4 Enclosures                                                                  •   Type 8 Enclosures
•        Type 4 enclosures are intended for indoor or outdoor use primarily to provide      •   Type 8 enclosures are for indoor or outdoor use in locations classified as
a degree of protection against windblown dust and rain, splashing water, and           Class I, Groups A, B, C, or D, as defined in the National Electrical Code.
hose-directed water; and to be undamaged by the formation of ice on the            •   Type 9 Enclosures
enclosure.
•   Type 9 enclosures are intended for indoor use in locations classified as Class
II, Groups E, F, and G, as defined in the National Electrical Code.
•   Type 10 Enclosures (MSHA)Type 10 enclosures shall be capable of meeting
the requirements of the Mine Safety and Health Administration, 30 C.F:R.,
Part 18.
Basic Electrical Formula:
Three Phase Systems
• Volts = I x R = amps x resistance

= Input Watts x PF
1000

= Input Kilowatts
KVA
Basic Electrical Formula:
Single Phase Systems
• Volts = I x R = amps x resistance
Conduit fill (sizing)

5” PVC, (3) 1/c 500MCM,
#1/0 G 15KV

5”   5.047   20.0   6.2   8.0   10.6

Sample Problem: Is 5 inch conduit sufficient for (3)
1/c00MCM 15KV + 1/0 Grd 15KV?

% fill =    total area of cables x 100
Area of Conduit
Area of Cable =
= 3 (p   x (1.49” Dia)2 + (p x (1.07” Dia) 2 = 6.13 inch2
4                          4
Area of Conduit = = 3 (p x (5.047” Dia)2 = 20 inch2
4

% fill = Area of conduitx100 =6.13 inch2 x100 = 30%
Total area of cables       20 inch2
Cable
Ampacity
per NEC
600 C
< 100A
The lug rating of CB,
starter, disc sw are based
on 75deg C. If specified in
spec then the wires can be
based on 75deg C

750 C
> 100A

900 C ambient
Conductor Sizing
• Sections 220-3(a), 220-10(b),
and 384-16(c). The NEC requires
for conductor sizing to be sized at
125% of the continuous load, plus
– Continuous Load: above 3 hours
i.e.. Lighting, HVAC motors
– Non continuous Load: less than 3
hours, i.e.. Bridge crane, elevators

•   Example: 175 amp continuous load
•   175A x 125% = 218.7A
•   Choose next size larger from NEC table 310.16a
= #4/0 AWG
Sizing Transformer CB and cable and conduits
based on 30 deg C ambient and 75 deg C cable

Example: 75KVA transformer = 125A CB, HV cable; 3#2 in 1 ½
“C, LV cable 3#4/0 & 1#6 in 2 ½”C
Transformer Formula
• Suppose we have a 500kVA, 480V delta/208 wye/120V transformer.
What are the transformer's primary and secondary currents?

ILine = (rated kVA x 1000) / (1.73 x VLine)
=(500 x 1000) / 1.73 x 480)
=500,000 / 830=603A

ILine =(rated kVA x 1000) / (1.73 x VLine)
=(500 x 1000) / 1.73 x 208)
=500,000 / 360=1388A
Ground Conductor Sizing
http://www.electrician2.com/calculators/t122_122.html

Equipment ground      (Ground                         System Ground (Ground
conductor for Service entrance)
Conductor for OCPD for motors)
Sizing Conductor and OCPD for Motors

example                                 Motor Full Load current NEC table 430.250
Motor Lock rotor Current NEC table 430-251 (b)
Example: 60HP, 150A MCP, 100A Disc      Cable Ampacity NEC 310.16
Switch, 3#2 + 1#6 in 1 ¼ inch conduit   Ground wire NEC 250.122
Rule of Thumb
Electrical principles

• Receptacle are usually rated 180VA but we usually only
put 5 or 6 per circuit because of computer loads.
• At 480V : 1HP = 1KW
• Min. size power circuit is #12AWG
• Instrument cable is #18 or #16 for single pair and #24 for
multi-pair
• Heat is your enemy in electrical design
• Energy is conserved in transformer: amps go up then
voltage goes down, volts go up then current goes down
Conclusion
•   Electrical Codes
•   Enclosures
•   Basic Electrical Formulas
•   Conduit Sizing
•   Cable Ampacity Table NEC 310-16
•   Conductor Sizing
•   Sizing Transformer CB, Cable and Conduit
•   Transformer Formula
•   Ground Wire Sizing
•   Sizing Conductor and OCPD for 480V Motors
•   Rule of Thumb

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