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04-10-2008, 02:19 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 ÷ D2I = 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 LI = 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 02:46 PM.

04-10-2008, 02:55 PM   #2

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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.

 04-10-2008, 03:11 PM #3 Member   Join Date: Apr 2008 Posts: 108 Rewards Points: 83 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?
 04-10-2008, 03:31 PM #4 Licensed electrician   Join Date: Sep 2007 Location: Maryland Posts: 10,441 Rewards Points: 1,036 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.
 04-10-2008, 05:29 PM #5 Electrician   Join Date: Aug 2007 Location: Connecticut, Litchfield Posts: 2,015 Rewards Points: 1,000 Keep in mind this is bare MINIMUM, please feel free to add as many more as you like.
 04-10-2008, 07:41 PM #6 Newbie   Join Date: Apr 2008 Posts: 25 Rewards Points: 10 Chris, That is a very nice diagram and notes to properly define the requirement. Nicely done.
04-10-2008, 11:42 PM   #7
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Quote:
 Originally Posted by Joba Fett Chris, That is a very nice diagram and notes to properly define the requirement. Nicely done.
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