|FCG|Frank
Active Member
Exactly.See... we need a formula for wpsf in LED terms.. actual watts may not mean jack ^^^umol is the only surefire way to measure as of now...
w/sq ft is an old method of calculating requirement and as you say it means nothing in the end, it's just an approximation. Especially when you consider that PAR readings are taken in uMoles/square meter/second. So the whole w/sq ft thing is so yesterday
For the CL lights, they have released exact PAR readings for the lights so we don't need a w/sq ft formula for LED when we get the exact PAR readings anyway.
But for comparison's sake, let's do it anyway!
Look at this PDF at page 21 then page 25: http://www.frankfcg.com/CLW_Pres.pdf
A canopy placed 18" directly under the center of a SS400W would receive about 922 uMoles/sq m/s of PAR.
The SS400W draws 320W of power
That is 2.88 uMoles/sq m/s of PAR generated per watt consumed at 18" from center of the light.
Now use that to plug it in the table I posted above and you can get an approx. value in w/sq ft if you know how much a particular HPS light emits in either LUX or FC since you know a HPS has 0.12 uMoles/sq m/s of PAR per 1 FC.