Lumen and Watt Gestimate

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Electriman

Senior Member
Location
TX
Greetings,

I understand that the total of Lumen that we would need to depends on the ceiling height, wall colors and so on. But I was wondering if I need to have x fc in a room, how much Lumen I need for that room roughly considering I know the dimensions.

The same question but for outdoor? If I want to have football field to have a X amount of fc, how much Lumen do I have to consider?

Lastly, what is the average range for Lumen/watt?

Thank you in advance.
 
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sameguy

Senior Member
Location
New York
Occupation
Master Elec./JW retired
Time for you to sit with:
1) google, there are minimum standards, residential has window lighting minimums, lighting manufacturers.
2) stop in at a lighting specifier, real electrical supply house,
3) many types of fixtures and lamps to just say, 5ft/candle for temp. lighting or other as an example.
I think your going to ace to do more leg/finger work.
 
tw1156

tw1156

Senior Member
Location
Texas
Electriman said:
Thanks it helped for indoor lighting. I am hoping the outdoor lighting is similar.
Click to expand...

Outdoor lighting can vary greatly between manufacturers when it comes to the optical distribution. There are many different types of Lighting levels for certain applications, similar to indoor lighting requirements. A manufacturer may claim the luminaire is equal (5000 lumens for example) but how they distribute that light may not be equal. This important because uniformity requirements(Max to Min ratios) may not be the same. For example Manufacturer A may have their fixtures placed to provide a uniformity ratio of 10:1 with an average of 1fc. Manufacturer B may come along and say they have the same lumens and a higher average, but they may not disclose that their uniformity is now at 20:1 (worse).

Be wary of recommendations regarding averages only, without regard for uniformity. Averages are a terrible way to convey lighting alone. For example, I could have a 100' x 100' area that is averaging 5fc, but it may mean I have 10fc beneath a pole, and have a 0.1fc somewhere else. The uniformity here would be 100:1! This same scenario could have an application achieving an average of 1fc, but it may have a 2fc maximum, and a 0.5fc minimum (4:1 max/min ratio), which would make the lighting job appear more uniform.

There's a lot to go into, but it starts with what your application is, and how you would approach lighting it.
 
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Electriman

Senior Member
Location
TX
tw1156 said:
Outdoor lighting can vary greatly between manufacturers when it comes to the optical distribution. There are many different types of Lighting levels for certain applications, similar to indoor lighting requirements. A manufacturer may claim the luminaire is equal (5000 lumens for example) but how they distribute that light may not be equal. This important because uniformity requirements(Max to Min ratios) may not be the same. For example Manufacturer A may have their fixtures placed to provide a uniformity ratio of 10:1 with an average of 1fc. Manufacturer B may come along and say they have the same lumens and a higher average, but they may not disclose that their uniformity is now at 20:1 (worse).

Be wary of recommendations regarding averages only, without regard for uniformity. Averages are a terrible way to convey lighting alone. For example, I could have a 100' x 100' area that is averaging 5fc, but it may mean I have 10fc beneath a pole, and have a 0.1fc somewhere else. The uniformity here would be 100:1! This same scenario could have an application achieving an average of 1fc, but it may have a 2fc maximum, and a 0.5fc minimum (4:1 max/min ratio), which would make the lighting job appear more uniform.

There's a lot to go into, but it starts with what your application is, and how you would approach lighting it.
Click to expand...

Thanks. My intention is not have glare and in order not to have glare, I am suggesting to keep the max to min ratio below 5. Min should never go below 10 fc.
 
tw1156

tw1156

Senior Member
Location
Texas
Electriman said:
Thanks. My intention is not have glare and in order not to have glare, I am suggesting to keep the max to min ratio below 5. Min should never go below 10 fc.
Click to expand...

Glare will not equal brightness. Glare is the angle at which the lumens are exiting the luminaire. The higher the angle (think 60° - 80°), the more perceived glare. The reasons why manufacturers may do this, is you can throw the light much further, but at the expense of glare.
 
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thewiseguy31

Member
For outdoor lighting, I would pick a manufacturer and have them do a layout for you. Local code enforcement will want to see that your FC levels are in range and that there is no spill-over into public areas. This is assuming you are looking to change out pole/area fixtures. If this is just a wall-pack replacement, then look to see what you are currently using and ask the manufacturer which fixture will give the equivalent.
 
W

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
1 foot candle is about 11 lux
1 lux is defined as 1 lumen per square meter

Won't help with the detailed design, but will help with give a ballpark number for the lumens needed, as a check for the more detailed calculations.

-Jon
 
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