Foot candles

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sparky76

Senior Member
Location
So Cal
Met A GC today for a TI. He didn't have plans just a scope letter. He says he needs a firm price w/o plans. Scope letter says 90 foot candles at 6 feet. The fixtures will be lay in parabolic troffers probably 4 lampers and its an 8' ceiling.
Are there any online tools to help me figure out how many fixtures I'll need to obtain that foot candle rating?
 
mivey

mivey

Senior Member
sparky76 said:
Met A GC today for a TI. He didn't have plans just a scope letter. He says he needs a firm price w/o plans. Scope letter says 90 foot candles at 6 feet. The fixtures will be lay in parabolic troffers probably 4 lampers and its an 8' ceiling.
Are there any online tools to help me figure out how many fixtures I'll need to obtain that foot candle rating?
Click to expand...
Firm price and requirments without firm details? Don't see it happening.

For a better calc, most manufacturers have IES data to go with their fixtures.

You can do a simple zonal cavity calc by:
footcandles = #luminaires * #lamps * lamp lumens * coefficient of utilization * light loss factor / length / width

but would be a rough calc. How tight are they going to hold you to the 90 fc. I'm assuming at 2 ft from floor (8 ft less 6 ft).
 
PCN

PCN

Senior Member
Location
New England
Try visual lighting software. The basic version is free, it's great for calculating footcandle levels and is loaded with hundreds of IES files. You can also import other files if your fixture is not listed.

Very simple to use. http://www.visuallightingsoftware.com/

As long as you have a good idea of reflectance values it's quite acurate.
 
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Ragin Cajun

Senior Member
Location
Upstate S.C.
sparky76 said:
Met A GC today for a TI. He didn't have plans just a scope letter. He says he needs a firm price w/o plans. Scope letter says 90 foot candles at 6 feet. The fixtures will be lay in parabolic troffers probably 4 lampers and its an 8' ceiling.
Are there any online tools to help me figure out how many fixtures I'll need to obtain that foot candle rating?
Click to expand...


Normal calculations are made at 30". 90fc at 6' with an 8' ceiling, a typo.

You don't need to be doing the engineering. Shame on the GC.
 
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