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#16708 11/15/02 05:54 PM
Joined: Oct 2001
Posts: 20
Being new at contracting, I get alot of design questions for lighting. To help make things easier, is there a number of watts per sq foot to help calculate the amount of lights and wattage of bulbs used? Just something to get a person in the ballpark, I seem to recall seeing something on that, but can't remember where. By the way this is just for residential. Thanks in advance for any help!!

#16709 11/15/02 06:21 PM
Joined: Nov 2002
Posts: 15
RR Offline
Start with Table 220-3(b) (NEC 1996). For Dwelling Units, the VA per square-foot is 3.

#16710 11/15/02 07:21 PM
Joined: Oct 2002
Posts: 210
The 3va per sq ft is for service calculation purposes.

#16711 11/15/02 08:57 PM
Joined: Jun 2002
Posts: 186
mj Offline
also see sbcci, for foot candal requirments

#16712 11/15/02 09:01 PM
Joined: Nov 2002
Posts: 267

I had to layout lighting for a commercial building years ago and wondered the same thing. They have calculators for lighting lay-out. The catalogs from the manufacturers have some design lay-out.Also the manufactures have design engineers to help you choose proper lighting heights and spacing. Lighting for a home is a little different. There's your basic codes for entering rooms, having a light switch. I really think it's personal preference for homes, kitchens require the most light usually, dimming light is good if you feel it's a room where they're not sure if they'll need all the light all the time. Hope that was some help. I know a lot of contractors try to avoid lighting because it always seems to be an issue, so they leave it primarily up to the homeowner to assume their own liability.

#16713 11/16/02 01:59 AM
Joined: Oct 2000
Posts: 2,722
Broom Pusher and
As stated, 3 VA / sq.ft. is for service load calcs, not for "how many Luminares to be installed". If so, a 10' x 10' room would require 300 Watts of light!
Very blinding in most cases [Linked Image]

For common projects, this would be something someone designs per the needs of the Client, so get their input and apply accordingly.

One member suggested SBCCI for suggested Foot Candle figures. Another is IEC. These figures are helpful in your overall design ideas.

On a similar note - here in California, we have Energy Conservation Codes to conform to. For Electrical, it's known as Title 24 part 6.
For a Residential job, service still is calced with 3 VA / sq. ft., but there are a few mandatory luminare and lamp types per room that must be used.

For a Commercial job, once again the service is sized with lighting VA / sq. ft., but the maximum installed total Wattage falls way below that figure.
For instance, an Office enviroment would allow a maximum of 0.9 Watts / sq. ft. The wattage figure includes the lamp wattage and ballast heat losses.

Good luck!

Scott s.e.t.

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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