Electrical Thumb Rules-Light Sources

 

Watts & Light Brightness

Incandescent Watts  CFL Watts LED Watts Lumens (Brightness)
40 8 to 12 6 to 9 400 to 500
60 13 to 18 8 to 12.5 650 to 900
75 to 100 18 to 22 13 to 15 1100 to 1750
100 23 to 30 16 to 20 1800 to 2779
150 30 to 55 25 to 28 2780

 

Minimum Lumens

Incandescent (Watt) CFL , Halozan , LED (Minimum Lumen)
25 Watt 200
40 Watt 450
60 Watt 800
75 Watt 1100
100 Watt 1600
150 Watt 2700

 

Wattage Comparison Chart

Incandescent
/
Halogens
Mercury Vapor Metal    Halide High
Pressure
Sodium
Compact
Fluorescent
(CFLs)
Light
Emitting Diodes
(LEDs)
40 to 60 15 to 25 5 to 15 5 to 15 12 to 15 5 to 8
60 to 75 25 to 35 15 to 25 15 to 25 15 to 18 7 to 10
75 to 100 35 to 45 20 to 35 20 to 35 18 to 23 10 to 15
100 to 150 50 to 60 25 to 40 25 to 40 23 to 35 15 to 20
150 to 200 70 to 85 35 to 45 35 to 45 30 to 45 20 to 25
200 to 250 90 to 110 40 to 55 40 to 55 45 to 60 25 to 30

 

Luminous efficacy

Light type Typical luminous efficacy (lumens/watt)
Tungsten incandescent light bulb 12.5 to17.5 lm/W
Halogen lamp 16 to 24 lm/W
Fluorescent lamp 45 to 75 lm/W
LED lamp 30 to 90 lm/W
Metal halide lamp 75 to 100 lm/W
High pressure sodium vapor lamp 85 to 150 lm/W
Low pressure sodium vapor lamp 100 to 200 lm/W
Mercury vapor lamp 35 to 65 lm/W

 

Selection parameter of LED Bulbs

Parameter Average Good Best
Lumens/Watt 75 90 100
Power Factor 0.7 0.8 0.9
CRI 60 70 80
LED Life in Hours 15000 25000 50000

 

Available CRI of Various Lighting Sources

Source CRI
Incandescent / Halogens >95
T8 Linear Fluorescent 75 to 85
Cool White Linear Fluorescent 62
Compact  Fluorescent 82
Metal   Halide 65
High Pressure Sodium (HPS) 22
LED 80 to 98

 

Color Accuracy – CRI Chart

CRI Rating
>90 Great
80 to 90 Very Good
70 to 80 Good
60 to 70 Good
40 to 60 Poor

 

Color Temperature & CRI Chart

Kelvin Light Effect CCT CRI
< 3600K Incandescent Fluorescent (IF) 2750 89
< 3600K Deluxe warm white (WWX) 2900 82
< 3600K Warm white (WW) 3000 52
3200K to 4000K White (W) 3450 57
3200K to 4000K Natural white (N) 3600 86
Above 4000 K Light white (LW) 4150 48
Above 4000 K Cool white (CW) 4200 62
Above 4000 K Daylight (D) 6300 76
Above 4000 K Deluxe Daylight (DX) 6500 88
Above 4000 K Sky white 8000 88

 

Color Temperature & CRI

Lighting source Color Temperature Color Rendering Index
High Pressure Sodium Lamp 2100K 25
Incandescent Lamp 2700K 100
Tungsten Halogen Lamp 3200K 95
Tungsten Halogen Lamp 3200K 62
Clear Metal Halide Lamp 5500K 60
Natural Sun Light 5000K to 6000K 100
Day Light Bulb 6400K 80

 

Lighting Source CCT

Source Color temperature in Kelvin
Skylight (blue sky) 12,000 – 20,000
Average summer shade 8000
Light summer shade 7100
Typical summer light (sun + sky) 6500
Daylight fluorescent 6300
Xenon short-arc 6400
Overcast sky 6000
Clear mercury lamp 5900
Sunlight (noon, summer, mid-latitudes) 5400
Design white fluorescent 5200
Special fluorescents used for color evaluation 5000
Daylight photoflood 4800 – 5000
Sunlight (early morning and late afternoon) 4300
Bright White Deluxe Mercury lamp 4000
Sunlight (1 hour after dawn) 3500
Cool white fluorescent 3400
Photoflood 3400
Professional tungsten photographic lights 3200
100-watt tungsten halogen 3000
Deluxe Warm White fluorescent 2950
100-watt incandescent 2870
40-watt incandescent 2500
High-pressure sodium light 2100
Sunlight (sunrise or sunset) 2000
Candle flame 1850 – 1900
Match flame 1700
Skylight (blue sky) 12,000 – 20,000
Average summer shade 8000
Light summer shade 7100
Typical summer light (sun + sky) 6500
Daylight fluorescent 6300
Xenon short-arc 6400
Overcast sky 6000
Clear mercury lamp 5900
Sunlight (noon, summer, mid-latitudes) 5400
Design white fluorescent 5200
Special fluorescents used for color evaluation 5000
Daylight photoflood 4800 – 5000
Sunlight (early morning and late afternoon) 4300
Bright White Deluxe Mercury lamp 4000
Sunlight (1 hour after dawn) 3500
Cool white fluorescent 3400
Photoflood 3400
Professional tungsten photographic lights 3200
100-watt tungsten halogen 3000
Deluxe Warm White fluorescent 2950
100-watt incandescent 2870
40-watt incandescent 2500
High-pressure sodium light 2100
Sunlight (sunrise or sunset) 2000
Candle flame 1850 – 1900
Match flame 1700

 

CCT – Correlated Color Temperature

Kelvin Associated Effects Type of Bulbs Appropriate Applications
2700° Warm White, Very Warm White Incandescent bulbs Homes, Libraries, Restaurants
3000° Warm White mostly halogen lamps, Slightly  whiter  than ordinary incandescent lamps Homes, Hotel rooms and Lobbies, Restaurants, retail Stores
3500° White Fluorescent or CFL Executive offices, public reception areas, supermarkets
4100° Cool White Office, classrooms, mass merchandisers, showrooms
5000° Daylight Fluorescent or CFL Graphic industry, hospitals
6500° Cool Daylight Extremely  white‘ Jewelry stores, beauty salons, galleries, museums, printing

 

Average Life Cycle

Source Average Life
Incandescent / Halogens 1,000 to 4,000 hours
CFL 6,000 hours
LED 15,000 to 50,000 hrs

 

Lamp Properties

Option Life (hrs) Efficacy (lpw) CRI Color of light
LED 35,000-50,000 30-300 ≥70 White
High Pressure Sodium 20,000-24,000 50-110 ≤40 Orange
Metal Halide 6,000-15,000 72-76 75-90 White
Mercury Vapor 16,000-24,000 30-50 40-60 Blue-White
Fluorescent 10,000-24,000 40-140 20-80 White

 

Illuminance Levels for Signage Lighting

Light Intensity Foot candles Lux
Low 10 to 20 100 to 200
Medium 20 to 40 200 to 400
High 40 to 80 400 to 800

 

Types of Lamp Technologies

Type of Lamp Luminous

Efficacy

(lm/W)

Color

Rendering

Properties

Lamp life in

Hrs.

Lamp life in

Hrs.

High Pressure

Mercury Vapor (MV)

 

35-36 lm/W Fair 10000-15000

 

High energy use, poor lamp life
Metal Halide (MH) 70-130 lm/W Excellent 8000-12000 High luminous efficacy, poor lamp life
High Pressure

Sodium Vapor

(HPSV)

 

50-150 lm/W Fair 15000-24000 Energy-Efficient, poor color rendering

 

Low Pressure

Sodium Vapor

(LPSV)

 

100-190

lm/W

 

Very Poor 18000-24000 Energy-Efficient, very poor color rendering

 

Low Pressure

Mercury

Fluorescent Tubular

Lamp (T12 & T8)

 

30-90 lm/W Good 5000-10000 Poor lamp life, medium energy use, only available in low wattages

 

EE Fluorescent

Tubular Lamp (T5)

 

100-120

lm/W

 

Very Good 15000-20000 long lamp life, only available in low wattages

 

Light Emitting

Diode (LED)

 

70-160 lm/W Good 40000-90000 High energy savings, low O&M, long life, no

mercury, high

 

 

Comparison of Lamp Technology

Technology Mercury Vapor High Pressure Sodium Vapor Induction New Ceramic Induction New Ceramic LED
Description Older Very Common white light  HID light source Most common HID light source used in street lighting White light electrode less light source with long operating life White light HID technology White-light, solid-state light source
Pros Low initial cost Low initial cost maintenance-free White light Small size
Longer lamp life Longer lamp life High efficacy Longer lamp life Very long time life
White light High lamp efficacy (70-150) lumens/watt) Excellent color rendering index High lamp efficacy (115) lumens/watt) Switching has no effect on life
Sudden failure are uncommon Instant start and restrike operations High fixture efficiency Contains no mercury
No flickering, strobing or  noise low ambient  temperature operations
Low temperature operations High lumens efficacy
No flickering, strobing or  noise
Instant start and restrike operations
Cons Poor lamp efficacy (34-58) lumens/watt) Low CRI High initial cost High price High price
Low fixture efficiency Contains mercury Low lamp efficacy (36-64 ) lumens/watt) Lower luminaire efficacy Low luminous flux
Contains mercury Contains mercury Higher electricity consumption CRI can be low
Contains mercury Risk of glare

 

Restrick Rate of Bulbs

HID lamp type Time to reach 80% light output Time to Restrike
Mercury 5-7 min 3-6 min
Metal halide 2-4 min 10-15 min
High-pressure sodium 3-4 min 1 min

 

Mounting Height of Light according to Types of Bulbs

HID lamp type Watt Mounting Height
Mercury 100 Watt 8 Meter
175 Watt 10 Meter
250 Watt 15 Meter
400 Watt 23 Meter
1000 Watt 30 Meter
Metal halide 70 Watt 7 Meter
100 Watt 10 Meter
175 Watt 16 Meter
250 Watt 20 Meter
400 Watt 25 Meter
1000 Watt 35 Meter
High-pressure sodium 35 Watt 6 Meter
50 Watt 7 Meter
70 Watt 8 Meter
100 Watt 12 Meter
175 Watt 18 Meter
250 Watt 25 Meter
400 Watt 30 Meter
1000 Watt 38 Meter

 

Various Lamp Comparison

As per CPWD

Lamp type Range Luminous LUX Efficacy (lm/W) Average  Life (hr) Color Rendering (Ra)
CFL    18W-36W 1200-2900 60-80 15000 75-85
Fluorescent-T5 28W-54W 2900-4850  90-104 24000  80-90
Fluorescent-T8   18W-36W 750-3250 50-90 20000 80-85
Fluorescent-T12  20W-40W 950-2450  48-61 12000 50-75
Halogen  50W 1200 24 2000 75-90
Metal halide 70W-250W 5300-25000 76-100 12000 70-90
High pressure sodium vapor 70W-1000W 5600-130000 80-130 20000 20-65
Low pressure sodium vapor 55W-135W 8100-32000 100-230 20000 20-65
Induction lamp 70W-150W 6500-12000 80-95 100000 65-90
LED     3W-120W 750-14000 80-100 80000 65-90

 

Lamp Comparison As per CPWD

Lamp type LED (Warm White) LED (Cool  White) T5 Lamp CFL Lamp HPSV  Lamp Metal Lamp Halide
CRI 80-85 75 85 85 22 60-90
Efficiency in lm/w 80 132 90 70 95-110 65-70
Usable lm/w 55-65 >100 75-85 50-60 55-65 35-40
Life (Hrs.) 50k+ 50k+ 30k 8-10k 24k 10k-20K

 

About Jignesh.Parmar
Jignesh Parmar has completed M.Tech (Power System Control), B.E(Electrical). He is member of Institution of Engineers (MIE) and CEng,India. Membership No:M-1473586.He has more than 16 years experience in Transmission -Distribution-Electrical Energy theft detection-Electrical Maintenance-Electrical Projects (Planning-Designing-Technical Review-coordination -Execution). He is Presently associate with one of the leading business group as a Deputy Manager at Ahmedabad,India. He has published numbers of Technical Articles in “Electrical Mirror”, “Electrical India”, “Lighting India”,”Smart Energy”, “Industrial Electrix”(Australian Power Publications) Magazines. He is Freelancer Programmer of Advance Excel and design useful Excel base Electrical Programs as per IS, NEC, IEC,IEEE codes. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & Knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.

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