Lighting Levels

[tkb]

I am designing a small training room at our shop and am wondering how to determine if I am specifying enough lighting.

The room is 30' x 24', with a 9' ceiling.

I am planning on 9 - 2 x 4 parabolic 3 lamp T8 fixtures.

Is ther any software or a way to calculate how many foot candles I will get at 30" above the floor?

 

[cadpoint]

I beleive you need to look into LDA (lighting design applications), there might even be an OSHA requirement for bench work which is higher than general office work lumination, as I recall...

Office is 70 Lumens

Bench work is 100 or higher

Don't hold me to the numbers...

 

[LarryFine]

Just off the cuff, 9 fixtures (3x3 pattern) seems to low for a room that size. I'd suggest 16 (4x4) for that room.

I drew a little ceiling-grid pattern of 1/4 of the room (12' x 15'). I'd put 4 fixtures in each quarter of that space.

 

[david luchini]

Is ther any software or a way to calculate how many foot candles I will get at 30" above the floor?

You can use the room cavity ratio method to calculate your footcandles.

http://aesl.hanyang.ac.kr/class/are141/zonal cavity ratio method.pdf

 

[dicklaxt]

Here is an example of what I have used over the years,its a simple quick substitute of numbers and some grade school math.

The formula is the number of fixtures required is equal to the footcandle requirement times the area of shop in square feet divided by the lumens per fixture times the co efficient of utilization(amount of light actually used) times the light loss factor(how clean a fixture is or kept).

Use .75 for your light loss factor and .65 for the co efficient utilization.

Once you have the required foot candles you want then adjust the fixture count to give equal spacing of the number of rows and the number of fixtures per row.

The spacing between rows should be approximately twice the distance from the centerline of the outside row to the wall dimension,,,,,,example if the centerline dimension of fixture to fixture is 6 feet row to row then the distance from the ourside row centerline to the wall should be 3 feet.I always kept the distance from the fixture end to the wall no more than 2 feet as the illumination out the end of a fixture is usually much less,for light uniformity end to end spacing should be kept to a minimum.I have seen some new fluorescents that claim otherwise.

Specific task lighting should be augmented with extra fixtures.

Just another way using industry standard foot candle requirments for the task at hand,

dick

 

[tom baker]

dicklaxt method is simple and will work. Or look in the back of a GE lighting catalog they have simplified lighting calcs.
And ask your wholesale house where you are purchasing the luminaires, they or the lighting rep can easily do the calc for you.
At the front of the room where you may have a wall screen for use with a projector, put those luminaires on a switch, otherwise they will wash out the screen. Could put in recess cans around the edges, or be able to switch some of the lamps off in a pattern.

 

[cadpoint]

I use to work for an Architect that hated ceiling tile panels of less than one foot in depth, they are very fragile. About eight inches they hold up...
My basic summary of the following statement is:

...
example if the centerline dimension of fixture to fixture is 6 feet row to row then the distance from the outside row centerline to the wall should be 3 feet.I always kept the distance from the fixture end to the wall no more than 2 feet as the illumination out the end of a fixture is usually much less,for light uniformity end to end spacing should be kept to a minimum.

One need's to load the lumuns to be slightly infront of a person sitting at the work bench or the work space, if the work space is againest the wall.