"Mike Hide" writes:

This question was asked a long time ago and several times since .I kept
one
response as I found it to be one of the most usefull, I was not the
originator ,i am just passing on the info ,it is as follows....

Glad you found it useful.


--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
Visit: http://home.earthlink.net/~lewhodgett for Pictures
++++++++++++++++++++++++++++

"Don't know who has asked the question or exactly what the requirements
are,
but let me offer the following based on having designed a few million sq
ft
of industrial lighting and having sold a few hundred thousand dollars of
lighting equipment in my time.

Assume a ceiling height of 10-12 ft max.

You have automatically eliminated all HID sources and are looking at a 2
lamp, HO, fixture for the application.

By definition, 1 lumen /sq ft = 1 foot candle.

Typical lumen efficiency over life of lamp = 90%
Typical lumen depreciation from dirt = 20%-30%
Typical lumen/watt output of a flourscent tube = 60-80 lumens/watt.

A great lighting level for a wood working shop would be 100 foot candles,
maintained.

Calculate the required number of fixtures as follows:

100 FC/0.9 Lumen efficiency/0.75 Dirt depreciation = 148 FC.

148 FC/70 Lumens/watt = Approximately 2 Watts/square ft of floor space.

If you have a 40 x 40 shop, that's 3200 watts of lighting required which
would mean 80, 40 watt tubes or 40, 2 lamp fixtures which would translate
into 4 rows of 10 fixtures each, 10 ft apart.

It's not rocket science.

It's the LGB theory of lighting design.

"Put one here, here, and here, and let's get a beer".


HTH


Lew "