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Old 04-10-2008, 01:19 PM   #1
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Lighting and recepticles


I have two questions. I am in the process of finishing my basement. The first question is how to estimate lighting needs. I am familiar with the IESNA guidelines and would like a reliable method to calculate my lighting needs. Is there a better way to do it than trial and error with a light meter? I have to imagine so. A nice formula of sq ft, lumens and/or foot candle, and distance from light source is all I would need.

Secondly, what does code require for receptacles? I sort of remember it being one receptacles per 10 ft of wall. Is this correct? What about a 17 foot wall length? Does that require 2 receptacles?

EDIT: Found the answser to question 1
Quote:
Calculating Light Level at a Point
For planes perpendicular to the direction of candlepower (Inverse Square Law):
Footcandles (fc) = I D2
I = Candlepower in candelas (cd) D = Direct distance between the lamp and the point where light level is calculated
Many workplanes are not perpendicular to the direction of light intensity, which is why calculating light level at a point is useful for such applications. In these cases, we often must determine light levels on workplanes that are not horizontal and perpendicular but tilted or even vertical. For tilted-horizontal or vertical planes:
Horizontal Footcandles (fch) = (I D2) x H
Vertical Footcandles (fcv) = (I D2) x L
I = Candlepower in candelas (cd) D = Direct distance between the lamp and the point where light level is calculated
H = Distance between the lamp and the point direct below on the workplane
L = Distance between that point and the point where light level is being calculated
D = Square Root of (H2 + L2) or D2 = H2 + L2

Calculating Average Light Level Throughout a Space (three formulas)
Average Maintained Illumination (Footcandles) = (Lamps/Fixture x Lumens/Lamp x No. of Fixtures x Coefficient of Utilization x Light Loss Factor) Area in Square Feet


Last edited by Bubbagump; 04-10-2008 at 01:46 PM.
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Old 04-10-2008, 01:55 PM   #2
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Lighting and recepticles


Receptacle spacing is commonly known as the 6-12 rule.

Within 6' of entering the room you need a receptacle. Then no more than 12' to the next one. Walls 2' or more wide would require a receptacle also. Fixed panels of sliding doors count as wall space.

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Old 04-10-2008, 02:11 PM   #3
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Lighting and recepticles


Ok, so say I have a 17x17 room and enter in a corner. On the wall to the immediate side I would need one at 6 ft from the corner where you enter, then another on the perpendicular wall less than 1 foot from the corner? (As 6+12=18 and would wrap to the next wall) Not a convenient layout as instead of 1 foot from the corner you would likely put 2 on the same wall, but I am just trying to understand the theory. Does that sound right?
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Old 04-10-2008, 02:31 PM   #4
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Lighting and recepticles


You could do that as long as there was no more than 12 foot between the receptacles. There is nothing stopping you from putting them every 2 foot if you want. Put them where you need and want them, plan for the furniture layout.

PS, the 6' in your example needs to be measured to both sides of the entry.
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Old 04-10-2008, 04:29 PM   #5
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Keep in mind this is bare MINIMUM, please feel free to add as many more as you like.

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Old 04-10-2008, 06:41 PM   #6
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Chris,
That is a very nice diagram and notes to properly define the requirement.
Nicely done.
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Old 04-10-2008, 10:42 PM   #7
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Quote:
Originally Posted by Joba Fett View Post
Chris,
That is a very nice diagram and notes to properly define the requirement.
Nicely done.
Note the copyright, I can't take credit for what is not mine.

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