Commercial space fixture selection and lumens per sq ft calculations

S

Stuntman

Member
Location
Midwest
Occupation
Electrical Engineer
I don't do lighting often, but I have a unique job that I am not sure how to approach.

14'6" ceiling, lighting must be surface mounted.
Three unique areas:
Mechanics area
Break Room
Paint/fine assembly area
Machine shop area

In the past, I have historically used 2'x4' 4 bulb troffers and shot for the 75lumens per sq ft +/-. This customer wants 4' LED (2 pin, T8 style) replaceable bulbs, so I can go with the same formula, but unsure if the LEDs warrant changing the setup.

1. Are 2x4 4-bulb LED troffers going to be too bright for a single fixture? I see a lot of 3 bulb and 2 bulb setups, but historically have always used 4-bulb if the ceiling was 10ft or greater.
2. Is there a simple rule of thumb for fixture spacing, particularly one that takes into account the ceiling height?
3. Is there a better lumen calculation for these unique lighting spaces (break room vs machine shop, etc)?

Thanks in advance.
 
Stuntman said:
I don't do lighting often, but I have a unique job that I am not sure how to approach.

14'6" ceiling, lighting must be surface mounted.
Three unique areas:
Mechanics area
Break Room
Paint/fine assembly area
Machine shop area

In the past, I have historically used 2'x4' 4 bulb troffers and shot for the 75lumens per sq ft +/-. This customer wants 4' LED (2 pin, T8 style) replaceable bulbs, so I can go with the same formula, but unsure if the LEDs warrant changing the setup.

1. Are 2x4 4-bulb LED troffers going to be too bright for a single fixture? I see a lot of 3 bulb and 2 bulb setups, but historically have always used 4-bulb if the ceiling was 10ft or greater.
2. Is there a simple rule of thumb for fixture spacing, particularly one that takes into account the ceiling height?
3. Is there a better lumen calculation for these unique lighting spaces (break room vs machine shop, etc)?

Thanks in advance.
Click to expand...
A common spacing I do in the labs I set up are 2x4 panels, with 4 feet between lights in the long direction, and 6 feet in the short direction. So that is one panel for 64 sq feet. I Cant remember the exact # of lumens these panels are, but usually they are around 6000. That puts us at 94 lm per sq foot. We go fairly bright in these labs. I have frequently done 4 retrofit tubes in a troffer and its totally fine, dont worry about it. Your typically 4' tube is 1900 lumens, so 7600 for 4, but you will lose some with the diffuser. I would have not problem using 4 per and just shoot for that 75 lm/sq ft figure so each fixture in a 100 sq ft square (or rectangle). I always tend toward higher, its never really too bright.
 
Thanks electrofelon, that gives me a place to start. I also notice that 6 bulb T5 style fixtures are becoming widely available and can be LED converted. Based on your comment, 6 bulb may not be too many?
 
You must log in or register to reply here.
Top