LED mounting height / lumens

[Schu338]

I have a commercial building approx. 40 x70 with a max. of 14' to bottom of roof decking. I am looking to replace my existing fluorescent fixtures with the UFO style-LED high bay fixtures. (So bottom of fixture would be approx. 13' above floor).

My question is does anyone think a 150W version with a lumen output of about 21,000 be too glaring at that height? My current fixtures (11) are 6 x 32-watt T-8 which is about 17,000 per fixture. They are bright but not too much glare. Hoping to replace the fixtures 1 to 1 without rewiring and get better lighting at some electrical cost savings.

Fixture suggestion?

 

[cybrdyke]

You can use much smaller ones if you want to. You dont actually get 17,000 lumens out of your 6 lamp fixture. It's more like 13,000 once you take into consideration dirt, age, and fixture losses.
If you went with 14,000 to 18,000 lumen UFO's, you would be outperforming your old T8's by alot.
UFO's can be glarey, especially at lower heights. You can find accessory glare shields or domed refractors. The glare shield is just a small "skirt" that goes around the fixture to cut off the diodes from your field of view.
Good luck,
CD

 

[Schu338]

You can use much smaller ones if you want to. You dont actually get 17,000 lumens out of your 6 lamp fixture. It's more like 13,000 once you take into consideration dirt, age, and fixture losses.
If you went with 14,000 to 18,000 lumen UFO's, you would be outperforming your old T8's by alot.
UFO's can be glarey, especially at lower heights. You can find accessory glare shields or domed refractors. The glare shield is just a small "skirt" that goes around the fixture to cut off the diodes from your field of view.
Good luck,
CD

Good idea, thanks. I'm thinking 15 x 100w fixtures now evenly spaced, rather than 11 x 150w. Will def look into the glare shields.

 

[Platonic Solid]

11 fixtures in a 40x70x14? You'd need 24 fixtures (4x6) for even light distribution regardless of lumen output. Next level is 18 fixtures (3x6). 15 fixtures (3x5) isn't ideal, but really depends what the space is for.

 

[theoldwizard1]

... My question is does anyone think a 150W version with a lumen output of about 21,000 ...

Whoa ! Mixing light bulb watts (which really only applies to old incandescant bulbs) with lumens, lux or candelas (3 realted, scientific way of measuring light) is JUST WRONG ! How To Measure Light In Foot-Candles, Lumens And Lux

The light source states it outputs 21,000 lumens, but at what distance ? I don't understand the standards completely, but I am guessing that is 1' away from the source. If that statement is correct, divide by the height, 13' and you get about 1,600 lumens at your surface.

... too glaring...

"Glare" is very subjective. It depends on the person and the surface the light is reflecting off of.

 

[cybrdyke]

Whoa ! Mixing light bulb watts (which really only applies to old incandescant bulbs) with lumens, lux or candelas (3 realted, scientific way of measuring light) is JUST WRONG ! How To Measure Light In Foot-Candles, Lumens And Lux

The light source states it outputs 21,000 lumens, but at what distance ? I don't understand the standards completely, but I am guessing that is 1' away from the source. If that statement is correct, divide by the height, 13' and you get about 1,600 lumens at your surface.


"Glare" is very subjective. It depends on the person and the surface the light is reflecting off of.

I know you're just trying to help. Let me help out here...
The light puts out 21,000 lumens. This number is just an indication of the brightness of the source, nothing more. Any other measurement of light from a certain distance is done in foot-candles, not lumens. To determine foot-candles you will need a computer and a lot of photometric information. You cant divide by the height or by anything else.
Glare is a specifically measured metric. It's the light from a source that's visible, but not usable. What IS subjective about glare is how it affects people differently.
CD

 

[GRB]

By far the easiest thing to do is change out the t8 for led “bulbs” and dump the ballasts. Still don’t have enough fixtures as others have mentioned but anything to avoid UFOs, particularly at that height.