CRI MEANING LIGHTING | WHAT IS CRI | CRI VALUE OF LAMPS

CRI MEANING LIGHTING 

When light falls on an object, it is a mea­sure of the amount of light that shows off its nat­ur­al col­or. The col­or ren­der­ing index (CRI) is the mag­ni­tude of the light source that most accu­rate­ly dis­plays the col­or of a surface. 

WHAT IS LUMEN 

The out­put of light is mea­sured in lumens or lumi­nous flux 

When a light source with a can­dela inten­si­ty is set at the cen­ter of the sphere with a meter radius, the amount of light source that falls on each m2 area on the sur­face of the sphere is one lumen 

LUX

The illu­mi­na­tion of a sur­face is mea­sured in lux. 1 m? The size of the lumen in an area is a lux 

Load Circuit Efficiency

When a lamp con­sumes 1 watt of pow­er, the num­ber of lumens it emits is lamp cir­cuit efficiency 

Colour Rendering Index

When light falls on an object, it is a mea­sure of the amount of light that shows off its nat­ur­al col­or. The col­or ren­der­ing index (CRI) is the mag­ni­tude of the light source that most accu­rate­ly dis­plays the col­or of a surface 

Lamps	Lamp watts includ­ing bal­last watts	Effi­ciecy Includ­ing ballest lumen per watt	Colour Ren­der­ing Index	Lamp life burn­ing Hours
Incan­des­cent Lamp	15,25,40,60,75,100,150, 200,300,500	8 to 7	100	1000
Flu­o­res­cent Lamp	18,20,36,40	30 to 80	65 to 77	5000 to 15000
Halo­gen	200,300,500,750,1000, 1500,2000	16 to 23	>90	2000 to 4000
Com­pact Flu­o­res­cent Lamp	8,12,15,28,32,45	26 to 60	80	8000 to 10000
High pres­sure Mer­cury Vapour lamp	80,125,250,400,1000, 2000	50 to 60	45 to 60	5000 to 8000
Met­al halide lamp	70,150,250,400,1000	50 to 70	70	8000 to 12000
High pres­sure Sodi­um Lamp	70,150,250,400,1000	80	25 to 60	12000 to 20000
Low Pres­sure Sodi­um Lamp	35,55,135	90 to 100	40 to 60	12000 to 24000

Light System Designing

When design­ing a light­ing sys­tem, one must first deter­mine the amount of lux required. It depends on where it can be installed and how it works. For exam­ple the lux lev­el for street light­ing and office light­ing will be different 

Inte­ri­or type	Ser­vice Range	Remarks
Gen­er­al office	300–500-700
Com­put­er work station	300–500-750
Con­fer­ence Room, Exec­u­tive office	300–500-750
Bank Counter, Office Area	300–500-750
Pub­lic Area,Banks	200–300-500
Auditorium,hotel	50–100-150	There should be a facil­i­ty for dim­ming the lights. Spe­cial lights should be set up in the areas between the seats
Entrance hall	50–100-150
Recep­tion, Cashier’s and Porter’s desk	200–300-500	Appro­pri­ate lights should be set in spe­cif­ic areas
Bars,cofee base din­ing airport	-	Design the lights to suit the ambi­ent conditions
Bed­room	30–50-100	Lights should be set up in addi­tion to the bed­side table and desks
Bath­room	50–100-150	It is desir­able to set the lights in addi­tion to the prox­im­i­ty of the face mirrors

Ener­gy con­ser­va­tion for tight­ing should be con­sid­ered when design­ing to set up a work­shop, home, or busi­ness. The best way to con­serve ener­gy for light­ing is to use as much nat­ur­al light as possible 

The amount of light set up in work areas should be high­er than that set in com­mon areas. This should be done while design­ing the system 

Esti­mate the num­ber of light fit­tings tak­ing into account the above. To esti­mate the num­ber of light fit­tings, first find the room index 

Different Energy Savings

Natural Day Light 

Busi­ness­es that use nat­u­ral­ly avail­able light dur­ing the day. It can reduce the ener­gy required for light­ing for indus­tri­al and pub­lic buildings 

Nat­ur­al day light can be used by plac­ing spe­cial­ly designed glass on the roofs of build­ings at spe­cif­ic intervals 

Large glass win­dows can be set up in office rooms to use nat­ur­al light. In addi­tion, although nat­ur­al light can be used more in oth­er ways, in fac­to­ries and offices, each method can be imple­ment­ed depend­ing on the facil­i­ties set up while design­ing the building 

This saves a great deal of ener­gy used by the skill of the archi­tects who design the buildings 

Light Fixture Reduction 

You can set timers on one of the street­lights and switch off the lights at cer­tain times of the night 

This can save ener­gy. Set­ting up good reflec­tors and increas­ing the illu­mi­na­tion can also reduce the num­ber of light fit­tings. Paint­ing the walls and ceil­ing well can increase the amount of light that is reflected 

Sim­i­lar­ly you can increase the retact as light depend­ing on the choice of floor tiles to be embed­ded in the floor. Anoth­er way is to set more lights in the work area and less lights in com­mon areas to reduce the num­ber of light fittings 

High Efficiency Lamps 

Illu­mi­na­tion should be done using lamps with col­or ren­der­ing index in the areas where the cor­rect col­or is to be expressed. Col­or ren­der­ing indices for GLS and halo­gen lamps are above 100 and 90, respec­tive­ly. Thus it is appro­pri­ate to use these types of lamps where the col­or should be prop­er­ly expressed 

How­ev­er, the effi­cien­cy of these lamps is very low. There­fore a large num­ber of lamp fit­tings will be required. This will increase the amount of pow­er used. 

Met­al halide lamps have a low­er col­or ren­der­ing index than GLS and halo­gen lamps. But their effi­cien­cy is very high. The effi­cien­cy of sodi­um vapor lamps is high­er than that of met­al halide lamps 

But the col­or ren­der­ing index is low. There­fore, it is more appro­pri­ate to use met­al halide lamps where the col­or needs to be prop­er­ly expressed 

Sim­i­lar­ly, sodi­um lamps can be used for street­lights where it is not nec­es­sary to express the cor­rect col­or. Their effi­cien­cy is high­er than oth­er lamps 

LED lamps are used as the next gen­er­a­tion lamps. But these are still in the process of being expand­ed. These types of lamps are cur­rent­ly used in the fol­low­ing locations 

1. Used as indi­cat­ing lamps on elec­tri­cal pan­el boards 
2. Used in traf­fic sig­nal lights 
3. Used as light in aircraft 
4. Used in emer­gency lights 
5. Used in dec­o­ra­tive lighting 
6. Used in portable lamps 

EFFECT OF REDUCTION IN SUPPLY VOLTAGE ON ENERGY CONSUMPTION 

When the sup­ply volt­age is reduced, the amount of pow­er con­sumed by all types of lamps decreas­es. But the volt­age must be reduced to the extent that the lamps do not flickering 

Using trans­form­ers and reac­tors, the volt­age can be reduced to oper­ate at a spe­cif­ic volt­age at a giv­en time. Reduc­ing the amount of volt­age will reduce the out­put of the lights 

There­fore, it should be set to oper­ate at a low­er volt­age when more light is not required. This also reduces the ener­gy for usable lights 

ELECTRONIC BALLAST AND LOW LOSS ELECTROMAGNETIC CHOKE 

Bal­lasts, which are usu­al­ly used to light lamps, take 15 to 20 watts of pow­er. But elec­tron­ic bal­lasts con­sume approx­i­mate­ly 1 watt of power 

The down­side of elec­tron­ic bal­last is that it injects unnec­es­sary har­mon­ics into the sys­tem. It costs 1.5 to 2 times more than reg­u­lar bal­lasts. Oth­er types of vac­u­um impreg­nat­ed cop­per bal­lasts are used 

These can take up to 7 watts of pow­er. And its low cost. 6. Pro­grammed timers using TIMERS AND OCCUPANCY SENSORS Micro con­trollers are now wide­ly avail­able in the market 

You can set the timer’s ON and OFF time and switch off the lights when the ligth is not required. Lights can also be switched off using infra red occu­pan­cy sensors 

Oth­er types of ultra­son­ic sen­sors are not avail­able in India. Occu­pan­cy sen­sors can be con­nect­ed to micro con­trollers to switch off the lights when no one is in the room. It may be help­ful to use occu­pan­cy sen­sors in areas where peo­ple occa­sion­al­ly use them 

FLUORESECENT TUBE LIGHTS 

The types of flu­o­res­cent tube lights are as follows 

1. T12: 40 watts, the diam­e­ter of the tube is ¹²⁄₈ “i.e. 33.8mm
2. T8: 36 watts, the diam­e­ter of the tube is 8/8 “i.e. 26mm 
3. T5: 14, 21,28, 35 watts, the diam­e­ter of the tube is ⁵⁄₈ ”i.e. 16mm 

T5 diam­e­ter tube light is short­er in length than T8 and T12 diam­e­ter tubes. Thus T5 lamps with high­er lamp effi­cien­cy are 50mm short­er than 8 and 12 lamps 

Also it only runs on elec­tron­ic choke. There­fore, when fit­ting 75 lamps in fit­tings with 12 and T8 light, spe­cial arrange­ments are required 

The effi­ca­cy of a 35 watts 15 lamp is 95 lumens / watt. But for 18 lamps it will be 89 lumens / watt, with elec­tron­ic choke. Mer­cury with glass does not absorb as the T5 lamp has a coat­ing on the inside of the glass 

Thus the use of mer­cury will be great­ly reduced 

CFL LAMPS

The col­or ren­der­ing index of CFL lamps is greater than 80. And their out­put is 55 to 67 lumens / watt 

CFL lamps are com­mon­ly used for floor illu­mi­na­tion in show­rooms, arte­facts, hotels, etc. CFL lamps are more effi­cient than GLS and halo­gen lamps