Lumen Method Lighting Calculation Example

Summary

This educational video script explains the process of calculating the number of light fixtures needed to achieve a desired illuminance level in a room. It covers key concepts like the utilization factor, light loss factor, and the impact of room color and finishes on light reflection. The script provides a step-by-step example using an 8x5 meter room with a target illuminance of 200 lux, demonstrating the formula rearrangement to find the required lumen output and the number of lights. It also discusses the efficiency of LED lighting compared to fluorescent, and the importance of maintaining light fixtures for optimal performance.

Takeaways

• 🔆 The video explains how to calculate the number of lights needed to achieve a certain illuminance level on a surface within a room.
• 📐 The formula for calculating the number of lights involves the illuminance, floor area, luminous flux of the lights, utilization factor, and light loss factor.
• 🕯️ The utilization factor accounts for the reflective properties of the room, such as wall color and finish, and the number of windows.
• 🧹 The light loss factor, also known as the maintenance factor, considers how often the lights are cleaned and their performance over time.
• 💡 LED lighting is more efficient and has less light loss compared to fluorescent lighting, especially if the fittings are cleaned regularly.
• 👀 The intensity of LED lighting can be too harsh for some people, but it's generally more efficient than fluorescent lighting.
• 📝 An example calculation is provided to determine the luminous flux required to illuminate a room measuring 8 meters by 5 meters with an illuminance level of 200 lux.
• 🛠️ The formula is rearranged to solve for the luminous flux (F), which is key to determining the number of lights needed.
• 🔍 The video provides a practical example using an office area and a 600 lumens LED panel light to calculate the number of lights required.
• ⚙️ For different activities, recommended illuminance levels vary; for example, general office work areas may need 500 lux, while supermarkets might require 1000 lux.
• 🏭 The video also simulates calculating the number of lights for an engineering workshop with a requirement of 1000 lux over an area of 20 meters by 10 meters.

Q & A

What is the purpose of the formula discussed in the video?

The formula is used to calculate the number of light fixtures (lumps) needed to achieve a certain illuminance level on a surface within a room area.

What are the two factors that account for the reduction in light output over time?

The two factors are the Utilization Factor and the Light Loss Factor, which account for the light's deterioration due to dust accumulation and reduced performance over time.

What is the significance of the Utilization Factor in lighting calculations?

The Utilization Factor takes into account the color of the room, the type of wall finish, the number of windows, and how reflective these surfaces are, affecting how light is distributed within the room.

What is another term for the Light Loss Factor?

The Light Loss Factor is also known as the Maintenance Factor.

How does the cleanliness of the environment affect the Light Loss Factor?

In a clean environment, the Light Loss Factor can be set higher, such as 0.9. In a very dirty environment, it might be set lower, such as 0.7, which increases the number of lights needed.

Why did fluorescent lighting often require tube replacement every six months?

Fluorescent lighting would deteriorate over time, turning yellow and reducing light output, while electrical power consumption remained the same. Replacing the tubes helped maintain brightness.

How does LED lighting differ from fluorescent lighting in terms of light loss?

LED lighting does not experience significant light loss if the fittings are cleaned regularly, making it more efficient and cost-effective compared to fluorescent lighting.

What is the formula rearranged to calculate the required luminous flux (F) for a given illuminance level?

The formula is rearranged to F = (E * A * UF * LLF) / n, where E is illuminance, A is area, UF is Utilization Factor, LLF is Light Loss Factor, and n is the number of lights.

How many lumens are required to achieve 200 lux in an 8m by 5m room with a Utilization Factor of 0.7 and a Light Loss Factor of 0.8?

The calculation would be 200 lux * 40 m² * 0.7 * 0.8, which equals 5600 lumens.

What is the recommended illuminance level for general work areas in offices according to the Chartered Institute of Building Services Engineers?

The recommended illuminance level for general work areas in offices is 500 lux.

How many lamps are needed to illuminate a 20m by 10m engineering workshop to a level of 1000 lux using 25-watt LED tubes with 2600 lumens each?

The calculation would involve using the rearranged formula for F and determining the total lumens required, then dividing by the lumens per tube to find the number of lamps needed.

Outlines

00:00

🔆 Understanding Illuminance Calculation

This paragraph introduces the formula for calculating the number of light fixtures needed to achieve a specific illuminance level in a room. It explains the importance of the utilization factor, which accounts for light reflection within the room, and the light loss factor, also known as the maintenance factor, which considers the reduction in light output over time due to dust accumulation and deterioration. The paragraph also contrasts LED lighting with fluorescent lighting, noting the reduced need for maintenance with LEDs and their more efficient light output despite a potentially harsher appearance.

05:00

📏 Calculating Luminous Flux for Lighting Design

The second paragraph delves into the process of calculating the required luminous flux to achieve a desired illuminance level in a given area. It provides a step-by-step guide on rearranging the formula to solve for the light output per fixture (F), taking into account the area, illuminance level, utilization factor, and light loss factor. An example calculation is presented for a room measuring 8 meters by 5 meters with a target illuminance of 200 lux. The paragraph also discusses the selection of appropriate light fixtures based on their lumen output and power consumption, using an LED panel light as an example.

10:04

🛠️ Applying Lighting Calculations in Different Settings

The final paragraph extends the discussion to practical applications, illustrating how to determine the number of lights needed for different environments, such as offices, retail spaces, and engineering workshops. It provides an example calculation for illuminating a workshop area with a high illuminance requirement of 1000 lux, using a 25-watt LED tube. The paragraph also touches on the importance of balancing the electrical load across multiple phases and considers factors such as power factor and breaker capacity to ensure a safe and efficient lighting installation.

Keywords

💡Illuminance

Illuminance refers to the total luminous flux incident on a unit area. It is measured in lux and is crucial in determining the amount of light required for a space. In the video's context, illuminance is the target light level, such as 200 lux, that needs to be achieved on the surface within a room area.

💡Luminous Flux

Luminous flux is the measure of the total amount of visible light emitted by a source. It is measured in lumens and is a key factor in calculating the number of lights needed to achieve a certain illuminance level. The script uses the term to describe the light output of the lamps being considered for installation.

💡Utilization Factor

The utilization factor accounts for the reflection and absorption of light within a space, influenced by factors such as the color and finish of the walls and the number of windows. It is used in the video's formula to adjust the calculation for the actual light that will be usable after reflections.

💡Light Loss Factor

Also known as the maintenance factor, the light loss factor represents the reduction in light output over time due to factors like dirt accumulation and lamp deterioration. The video mentions setting this factor based on the cleanliness of the environment, affecting the number of lights needed.

💡LED Lighting

LED lighting is a type of energy-efficient lighting technology that emits light by electrifying semiconductor materials. The video discusses the efficiency and longevity of LED lights compared to fluorescent lighting, noting their lower maintenance requirements.

💡Fluorescent Lighting

Fluorescent lighting is a traditional lighting technology that uses electricity to excite mercury vapor, producing ultraviolet light which then excites a phosphor coating to emit visible light. The script contrasts this with LED lighting, mentioning the need for periodic replacement of tubes to maintain brightness.

💡Lumens per Watt

Lumens per watt is a measure of a light source's efficiency, indicating how many lumens of visible light it produces per watt of electricity consumed. The video uses this metric to compare the efficiency of different lighting options.

💡Color Temperature

Color temperature refers to the appearance of the light emitted by a source, measured in Kelvins. It affects the perceived warmth or coolness of the light. The video mentions a color temperature of 6500K, which is a cool white light suitable for certain work environments.

💡Efficacy

Efficacy in lighting refers to the amount of light produced per unit of energy consumed, often expressed in lumens per watt. It is a key consideration in the video when selecting lighting to ensure energy efficiency.

💡Circuit Breaker

A circuit breaker is an electrical safety device designed to protect electrical circuits from damage caused by excess current. The video discusses the importance of selecting the right circuit breaker to handle the total current of the lighting installation.

💡Power Factor

Power factor is a measure of the efficiency with which electrical power is being converted into useful work. The video uses a power factor of 0.9 to calculate the total current required for the lighting system, indicating the efficiency of the electrical system.

Highlights

The video explains how to calculate the number of lights needed to achieve a specific illuminance level on a surface within a room.

The formula for calculating the number of lights includes illuminance, floor area, luminous flux, utilization factor, and light loss factor.

Utilization factor accounts for the reflection and absorption of light by room surfaces and colors.

Light loss factor, also known as maintenance factor, considers the deterioration of light output over time due to dust and cleaning frequency.

LED lighting is more efficient and has less light loss compared to fluorescent lighting, especially when fittings are cleaned regularly.

Example calculation provided to determine the luminous flux required to illuminate a room measuring 8 meters by 5 meters with an illuminance level of 200 lux.

Rearranging the formula to find the luminous flux (F) needed for a given illuminance level, area, utilization factor, and light loss factor.

The importance of understanding transposition in mathematical formulas for electrical students to simplify calculations.

A practical example of calculating the number of LED panel lights needed for an office area with a specific illuminance level.

Different recommended illuminance levels for various environments, such as offices, retail spaces, and engineering workshops.

The impact of color temperature on the perception of light intensity and the preference for a cool white light in certain settings.

A step-by-step guide on how to calculate the total current required to illuminate a workshop area with a specific number of lights.

Considerations for electrical safety, such as the number of devices per circuit breaker and the use of three-phase power distribution.

The use of inrush current and power factor in calculating the total current draw for a lighting installation.

Strategies for balancing lighting across multiple phases to ensure continuity in case of a phase loss.

The video concludes with a summary of the importance of accurate lighting calculations for various environments and applications.

Transcripts

so in this video we're going to explain

how to calculate the number of lumps

within a room area to provide an

illuminance on the surface so basically

what we have in this formula is we have

so n number of lights is the illuminance

times the floor area times the actual

luminous flux of the lumps that you fit

in the utilization factor and the light

loss factor so let me explain what these

two the utilization factor it's a light

loss factor so the moment we install our

light source at the moment that the

lighting installation is put into

service the light start to get dusty the

light performance deteriorates so over a

period of time the light will reduce the

output from the light will be reduced so

for that reason we put that factor into

our calculation the other type of factor

is the coefficient utilization

now this is takes into account the color

of the room the walls the type of finish

on the walls are those reflective of the

imap finish how many windows there are

in a room

so the coefficient light utilization

that is effectively what the light is

going to be reflecting from within the

room area so the light loss factor is

also known as the maintenance factor so

there was how often are the lights going

to be cleaned so typical factors if it's

a clean environment we can set a point

now but it's a very dirty environment

then we can sell at 0.7 and what that

does is that increases how many lights

we need so often is the case on a brand

new light installation if you've just

finished an installation in a workshop

area like a supermarket when you first

turn those lights on they're really

really bright and it's like wow you know

it's daylight but all the time

that will deteriorate and the like

especially old fluorescent lighting when

it starts to get all starts to

deteriorate it goes yellowy and what is

for sure is that the electrical power

consumption doesn't change but the light

output does change so often was the case

with fluorescent lighting is that you

would do what we call tube runs so you

would go six months twice a year you

would replace all the tubes in a factory

and the light would be absolutely

brilliant when you finished but that's

expensive with LED lighting that's not

the case as long as the fittings are

cleaned then they you don't get much of

a light loss you get zero light loss

with LED lighting compared to that and

fluorescent lighting the only downside

with other day like this some people

find it can be a little bit too intense

they can find that it's it's a little

bit too harsh on the eye so I still

think was ways to go with a lady like

him but it's certainly more efficient

than fluorescent lighting so let's look

at an example here so if we have a we're

going to calculate luminous flux

required to illuminate a level of 200

looks so that's one so what you see on

the surface in a room measuring 8 meters

by 5 meters so first thing we need to do

is we need to obviously get this formula

layer and then we need to rearrange the

formula R in this so any number of

lights eg luminance is the area F is the

light output in lumens

that's the utilization factor and that

is the light loss factor also known as a

valence factor so what we need to work

out well we need to work out the

luminous flux so we need to make F the

subject

okay so let's rearrange this formula to

find F so the first thing I'm going to

do is we're going to multiply both sides

by F so let's do that

so we'll write this out here

transposition is one area which a lot of

electrical students struggle with so my

advice is get on top of it early and

then that way your life is a lot easier

so now we've done that we multiply both

sides by F that gets rid of that gasket

that's gets rid of that so we are left

with now so n times F equals e a of BOF

times L F so now we need to get rid of n

so what we do is we divide that side by

n okay and obviously we put in on that

side so that will go there like so well

because obviously the bottom lines are

all times in yep see product is subset

of the quotient that will go up that

wall girl

so then we'll be left with F is

luminance times area a lot of times in

that of a utilization factor it sounds

like loss factor times number of lights

so let's look at our that way lights

we've got so the area is 85 so the area

8 by 5 so that's gonna be 40 meters okay

the illuminance level is going to be 200

looks from the question the UF and LF a

point seven point eight so UF is now

point seven and the LF is not point

eight

okay now as we don't know how many

lights we've got at the moment we're

gonna set I'm gonna set the number of

lights just to want so that's that that

will give you know what the whole light

would be then what we would do then is

we would look at divide in that level of

luminous flux into the illumise flux per

light and that will tell us movie how

many likes we need so we've put put

those calculations in so f so we have

200 times 40 of 0.7 was 8 times 1 so

we've done the math on there we get

fourteen thousand two hundred and eighty

five point seven one lumens that's the

talk about illumination

sorry lumen output required to provide a

two hundred looks within a five be eight

meter area so the question is is how

many of these what sort of lamps we're

going to fit well I have just got online

unless you say this was an office area

and you can see there that the power for

each light there is 40 watt so I've just

search for a 600 600 LED panel light

it's white and it's giving out a lumens

of 3500 so one panel light there so if I

was to do my sketch there so one power

light is gonna give out 3400 lumens

yeah okay so how many likes do we need

we'll all we do is we divide three

thousand four hundred lumens into 14

thousand two hundred and eighty five

point seven so number of lamps is to

talk lumens required divided by the

lumen per lamps or our LED light three

thousand four hundred lumens per lamp

divide the two we get four point two

well obviously you can get four point

two lamps so that's five lumps so if we

look at the actual

flower area then we just need to equally

divide the lumps into five now you might

ask yourself that's not a lot of lumps

for that solve area but remember we are

only asked to provide 200 looks so 200

looks isn't really a lot of light to

work in so if we wanted to increase the

amount of illuminance at the floor then

we would put more lights in so basically

if we look at the recommended light

levels

so for sabzi the Chartered Institute of

building service engineer's guides they

say the following level so offices

general work areas 500 Lux drawing

boards 750 looks so it depends on the

activity that's going on so if it's a

computer room offices work sessions and

it's quite a low looks area because you

don't want a lot of glare off the lights

because obviously people are tuned into

the toilet at the monitors retailing

though is very high so thousand looks

for your superstars you hypermarkets

supermarkets so that's why when you walk

in to these places they're really bright

you know and obviously the light in the

high bare lighting produces quite a lot

of lumens your engineering workshops

well it depends on the activity so if

you are quelled in 300 looks right the

way up to 2,000 looks so this depends

very much on inspection and testing so

if you are building engines or

assembling electronic circuits and so on

then you're going to need a very very

high level of looks you know for the

detail so this is a good guide to give

you an idea you know where to start and

how many lights you would need so let's

look at an example then and we're going

to simulate a workshop area and we're

going to work out how many lights we

actually need to illuminate a

engineering workshop up to a value of a

thousand looks that's the next example

then we have a factory floor or workshop

floor of 20 meters be 10 meters

and we're going to use a 1500 mil 25

watt LED tube and I've gone online and

you can see just literally searching

online for LED data you can see that

this is a 24 input power and the lumens

is obviously to 2600 and the efficacy

lumens per watt is 109 what we're gonna

do here also tell you about the color

temperature so it's nice and cool so

6500 that's gonna be a nice white clear

light so first thing we need to do is

we're gonna work out how many lumps are

required and we're gonna work out the

total current taking to illuminate the

area okay so the day when the thousand

looks in this area okay Michael's back

to his point eight that is a little bit

state but I'm setting up point eight

anywhere and the utilization factor is

not 0.7 so first thing we do is we write

our formula down and we do the maths

we've got our formula so the illuminance

required is a thousand the area is 10

meters by 20 meters okay and the lumen

output per light is 2600 the utilization

factor is not 0.7 and the light loss

factor is 0.8 so the total number of

lights we do the maths so that's one

hundred and thirty-seven point three six

lumps or 138 lamps so that means is we

would need to divide this floor area

basically we would need to 1500 each so

you would space out that floor area to

put multiple rows of lights now if it

was myself obviously I would put those

over three phases so you put them with

three phases so they're nice and

balanced there there's no risk Astral's

copic effect well obviously we need to

keep our face is balanced so how much

current is that going to take them well

if there's a hundred and thirty-eight

lamps so we've got one hundred and

thirty-eight lamps yeah times and the

input power is twenty four twenty four

what some not a lot really if you think

about it so so we get

total power of 3.31 kilowatts which is

that's quite a bit okay but obviously we

do that over three phases but we'll stay

with one phase for now now if you look

at the electrical data you can see there

that the there is an inrush there but

basically ignoring the inrush for now

power factor is greater than 0.9 and it

says there the number of devices per 16

the second trick is 72 so see 16 so you

or not you can only put 72 fittings on

the C 16 breaker so let's have a little

look and see we can work out the the

current on this now okay one second so

we've got so we know we've got 3.3

kilowatts the total power I times V

times power factor I'm going to set the

power factor at nine point nine so we

rearrange the formula for I power is V

times power divided by bolts times power

factor so there's point nine worst case

scenario and we get a total current of

16 amps now that's total obviously we've

got one hundred and thirty-eight

fittings so we're going to need to

divide it up so my advice to keep it

over three phases 16 over three gives us

five point three three amps per phase

and that's so that's obviously 46 lamps

per face or forty-six tubes and the talk

to allow for a total in rush I would

probably go for a c10 circuit breaker on

there so over three phases and the

beauty we're doing it over three-phase

is it should you lose a phase in

emergency you don't lose you've got

another two phases to keep you going

okay I hope you found that useful any

questions please let me know thanks for

watching