Input information
These are the input data for the following calculation:
- An office area has length: 20 meter; width: 10 meter; height: 3 meter.
- The ceiling to desk height is 2 meters.
- The area is to be illuminated to a general level of 250 lux using twin lamp 32 watt CFL luminaires with a SHR of 1.25.
- Each lamp has an initial output (Efficiency) of 85 lumen per watt.
- The lamps Maintenance factor (MF) is 0.63 ,Utilization Factor is 0.69 and space height ratio (SHR) is 1.25.
Calculation in 8 steps
1. Total wattage of fixtures:
| Total wattage of fixtures = Number of lamps x each lamp’s watt. |
| Total wattage of fixtures = 2 × 32 = 64 Watt. |
2. Lumen per fixtures
| Lumen per fixtures = Lumen efficiency (Lumen per Watt) x each fixture’s watt |
| Lumen per fixtures = 85 x 64 = 5440 Lumen |
3. Number of fixtures
| Required number of fixtures = Required Lux x Room area / MF x UF x Lumen per fixture |
| Required number of fixtures = (250 x 20 x 10) / (0.63 × 0.69 × 5440) |
| We will need 21 fixtures |
4. Minimum spacing between each fixture
| The ceiling to desk height is 2 meters and space height ratio is 1.25, so: |
| Maximum spacing between fixtures = 2 × 1.25 = 2.25 meter. |
5. Number of required rows of fixtures along with width of room
| Number of rows required = Width of room / Max. spacing = 10 / 2.25 |
| Number of rows required is therefore = 4. |
6. Number of fixtures required in each row
| Number of fixtures required in each row = Total Fixtures / Number of rows = 21 / 4 |
| Therefore, we have 5 fixtures in each row. |
7. Axial spacing between each fixture:
| Axial spacing between fixtures = Length of room / Number of fixtures in each row |
| … and that would be: 20 / 5 = 4 Meter |
8. Transverse spacing between each fixture:
| Transverse spacing between fixtures = Width of room / Number of fixtures in row |
| … and that would be: 10 / 4 = 2.5 Meter. |
5 things to conclude
So far, we have been calculated the following:
- Number of rows with lighting fixtures = 4
- Number of lighting fixtures in each row = 5
- Axial spacing between fixtures = 4.0 meter
- Transverse spacing between fixtures = 2.5 meter
- Required total number of fixtures = 21
The room height is not considered and This Calculation result is different when calculated in Lighting Software like Dialux and Relux
how can i get utilization factor and SHR please a little beat explanation
Distance of fixtures along width is 2.5 m as per the calculation. But the diatance of fixtures along length is 4m based on the number required is 21.But if we do so distance between fixtures along the length is 4 m which is above 2.5m. Won’t this effect illumination lenght wise?? Because as per SHR maximum allowed distanve between light fixtures is only 2.5m..??
how can i get utilization factor,initial lumen in a lamp and SHR please a little explanation
Dear Jignesh Parmar,
i am Ravi. i need one information. the above lighting calculation how did you get the Each lamp has an initial output (Efficiency) of 85 lumen per watt. please exaplain me. i am not getting this value.
thanks
ravi gm
How to calculate the no of fixtures required shed length 59 meters x width 28 meters x height 9 meters with hi bay fitting
1 lx = 1 lm/m2
Area = 59 (Length) *28 (Width) = 1652 Sq. Meters
Average Lumen Required for the Application: i.e: 150
Total Lumen = 150 Lumen * 1652 Sq. Meters = 2,47,800 Lumens
Now Find Fitting Lumen = Say 100W, (150Lumen/Watt= 15000 Lumen Fitting we would like to use
No. of Fittings = Total Lumens/ Lemen per Fitting = 247800/15000= Approx. 17 Nos. of Fitting
We also have to consider Height of Installation with Beam Angle of Light which can Increase or Decrease no. of Fittings
Please do not hesitate to contact us for further information if required to info@eledea.in
Thanks in advance,
Bhavin Patel
Room Height not considered in calculation, How to considered Room height in illumination manual cal.
Hey, i was wondering how to find the Utilization Factor for a light?
dear sir
i need to know the no of lights ( high bay required) for a shed having lenght,breadth and height of 73 mts 33 mtrs and 9 mtrs respectively. the highbay have 130 lumens per watt at source 120 beam angle and are of 100 watts . the lux level is of 250 . can you please let me know the no of fixtures requird
thanks
Shall we give distance irrespective of because diffusers are designed if I alligned to diffuser line the distance is x_4x -x is there if I’ll not arrenge like that light fixture looking like odd in the ceiling how can I do now
can u help how to calculate illumination factor for 4 tube lights of 40 watts inside and outside led bulbs are putting on a hub how to calculate the spacing
How i can calculate SHR in lighting calculation
i need to know what is the relation between No. of Light and lumens while increasing mounting height of the light.
also what is the recommendation for industries. how can i able to find Spacing Height Ratio? Where to i got this?
20x 400w son floodlights are mounted on a 12pole at the middle of each of the side of a square area of 40m side. calculate utilization factor ,the average illumianace on the area, the illuminance at any corner point. GIVEN : the total initial lamp lumen is 50 klm, D.F=0.8, MF=0.75, loss factor=0.9
It’s verry interesting!
Your work is very good . I appreciate it so much . My question is , if u are really keen to share your knowledge in the field of electrical Engineering , how would one communicate to you ?
Thank you very much.
Your clarification and description is very interesting and simple, thanks too much, in this regard I want to ask some questions:
1. should i take into consideration the clean factor (1.27-1.33), ie the values of numbers will be multiplied with this factor and therefore no of luminaries will increase.
2. for a certain space, it should be identified the color of ceiling, wall& floor and material type to get the reflecting factors and g with room index through the data table of the chosen lamp to get UF and this data no longer be available for the new models of lamps! how can we deal with this issue? appreciate your reply.
how can i download this in pdf form
How can I download this article format PDF
Thank you very much
Number of rows with lighting fixtures = 4
Number of lighting fixtures in each row = 5
Required total number of fixtures = 21
TOTAL NUMBER OF FIXTURES SHOULD BE 20 OR 21?? IF 21 PLEASE EXPLAIN ? ACCORDING TO DATA AT THE BOTTOM SIDE (ALSO MENTIONED IN 1ST 2 LINES OF COMMENT) I THINK SO TOTAL NUMBER OF FIXTURES SHOULD BE 20.
REGARDS
how to download this one?
tiny mistake in figures..
step 4: spacing should be 2.5 instead of 2.25…1.25×2=2.5..
step 5: the calculation sticks to 10/2.5=4
Nice demonstation of a classical calculation without the help of a fat light planning software.
But let me please make some comments: A lighting level of 250 Lux for an office area is not compliant to standards. For offices you should plan with 500 Lux instead.
Also I would consider to use not CFL but linear fluorescent lamps (T5), which have much higher efficiency of approx. 100 Lumen per Watt. Than you get also a better MF of 0,8 and this together reduces the number of fixtures.
how can i get utilization factor, initial lamp lumen and SHR please a little beat explanation
Thanks a lot its useful mostly to me because am still a fresher in the field of engineering.
Sir if I post a picture could you tell me how to solve this sum