Correct LED lumens to match/improve upon existing 2x4 flurrescent troffer

dinotone

Member
Location
Milton

I'm replacing 2x4 troffers (lay ins), each housing 4 x 40watt cool white T12s. So doing the basic math, these traditional T12s produce ~2600 lumens x 4 = 10,400 lumens. BUT most of what I see out there for 2x4 LED troffers is between 4,000 and 7,560 lumens. I know the T12s will lose some lumens over life, but I know I'm missing some other basic fact, when comparing (replacing) fluorescent lumens to LED lumens.

I want customer to be happy with light output and want to but the right replacement the first time.

Appreciate guidance here. thanks, Dino
 

brantmacga

Senior Member
Location
Georgia
Occupation
Electrical contractor
You may wish to add fixtures to maintain the lighting level. Idk about T12, but T8 fixture lumen efficiency is around 80%.

Lithonia’s 2GTL troffers are available with 14,000 lumen output.

They have an 8800 lumen fixture that should be pretty equal to the T12 fixtures when new.

Take a look at the photometric sheets and compare to the existing layout and ceiling height to see what you think would work best. Keep in mind windows and such that will bring in enough natural light during the day.

Usually on a 9-10’ ceiling we’re using 4800 lumen fixtures spaced 4’ apart.






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Strathead

Senior Member
The lumens don't correspond because with LEDs the light can be directed more efficiently.
To expand upon this, my understanding is lumens are the full output of the lamp, and they don't truly represent the light output of the fixture. So, fluorescent tube emits lights on a 4 foot axis at 365 degrees. The lumens are a measurement on the sum of light put out n the full 360 degree spectrum. The actual amount of light the fixture puts out will be affected by how the light is reflected around from the back, etc. Lumens also don't reflect the distribution of light. That is why the way to accurately figure out the affect of a light fixture you need to use photometrics charts. Footcandles are the affect of a light source, and it is measured at a location. This has caused a lot of people to be dissatisfied with the change to LED fixtures when it is not properly designed.
 

Amon

Member
Location
Denver, CO

I'm replacing 2x4 troffers (lay ins), each housing 4 x 40watt cool white T12s. So doing the basic math, these traditional T12s produce ~2600 lumens x 4 = 10,400 lumens. BUT most of what I see out there for 2x4 LED troffers is between 4,000 and 7,560 lumens. I know the T12s will lose some lumens over life, but I know I'm missing some other basic fact, when comparing (replacing) fluorescent lumens to LED lumens.

I want customer to be happy with light output and want to but the right replacement the first time.

Appreciate guidance here. thanks, Dino

>>>>A 40w 2x4 is going to put out good light....Its comparing apples to oranges. t12s are throwing the light 360 degrees. The LED is probably 110 or 120. Its called "delivered" light. Download a free lumen meter app for your phone and take reading before and after. Even if you have crap 2x4s that are 3yrs old it will still be about 20% more light. Also stay with 4k most likely if its any kind of an office. Or there are tunable 2x4s. 2.7k-5k
 

sameguy

Senior Member
Location
New York
Occupation
Master Elec./JW retired
To expand upon this, my understanding is lumens are the full output of the lamp, and they don't truly represent the light output of the fixture. So, fluorescent tube emits lights on a 4 foot axis at 365 degrees. The lumens are a measurement on the sum of light put out n the full 360 degree spectrum. The actual amount of light the fixture puts out will be affected by how the light is reflected around from the back, etc. Lumens also don't reflect the distribution of light. That is why the way to accurately figure out the affect of a light fixture you need to use photometrics charts. Footcandles are the affect of a light source, and it is measured at a location. This has caused a lot of people to be dissatisfied with the change to LED fixtures when it is not properly designed.
This
The lamp itself blocks light from moving out of the ixture.
 
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