lighitng calculation

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MBLES

Senior Member
when figuring lighitng calculations for residential are you suppose to
use fixture max wattage or the type of lamp that will be installed.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
when figuring lighitng calculations for residential are you suppose to
use fixture max wattage or the type of lamp that will be installed.

You would do that for the branch circuits but for the calc for the residence it is figured in at 3 watts/ sq. ft.
 

MBLES

Senior Member
You would do that for the branch circuits but for the calc for the residence it is figured in at 3 watts/ sq. ft.

I plan on putting 75w recessed cans all throughout the house MY lighting
dwelling calcu seems to be less that my actual installations of lighitng
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I plan on putting 75w recessed cans all throughout the house MY lighting
dwelling calcu seems to be less that my actual installations of lighitng
That may be true but what is the likelihood that all these fixtures will be on at once? Residential service are figured based on the diversity of the loads that are present. That is why we have Table 310.15(B)(6) which allows us to use a smaller conductor in most cases than T. 310.16 would allow.
 

MBLES

Senior Member
That may be true but what is the likelihood that all these fixtures will be on at once? Residential service are figured based on the diversity of the loads that are present. That is why we have Table 310.15(B)(6) which allows us to use a smaller conductor in most cases than T. 310.16 would allow.

Dennis I am new at pulling permits for residential I normally do comm/indust
So what u r saying is that all that may be required is the the singlefamily
dwelling service calculation general lts/recp, small appli, laundry and fixed
appliances plus a/c thats it I may not have to show panel schedule or
load analysis
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Dennis I am new at pulling permits for residential I normally do comm/indust
So what u r saying is that all that may be required is the the singlefamily
dwelling service calculation general lts/recp, small appli, laundry and fixed
appliances plus a/c thats it I may not have to show panel schedule or
load analysis

Well I have never been required to do a load calculation on a dwelling. I have done them but no one has ever asked for it. You need to read art. 220 but here is an online single family dwelling calculator. See if this helps
 

Mike01

Senior Member
Location
MidWest
Max allowed

Max allowed

220.12(D) LUMINAIRES: ?An outlet supplying luminaire(s) shall be calculated based on the maximum volt-ampere rating for the equipment and lamps for which the luminaire(s) is rated.? To me the key word is ?maximum? if the lamp holder of luminaire is UL listed and labeled for example a 100W max you load calculation has to indicate the maximum wattage allowed because you do not know what the home-owner or tenant (if commercial application) will install once you are complete. Unless you can get the manufacturer to re-label it otherwise (lower max wattage lamp) you have to use the maximum the luminarie is listed for.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
To me the key word is ?maximum? if the lamp holder of luminaire is UL listed and labeled for example a 100W max you load calculation has to indicate the maximum wattage allowed ...
Of course, that refers to the circuit calc; for the premises load calc, the per-sq-ft allowance is all you need.
 

Mike01

Senior Member
Location
MidWest
Calculations

Calculations

True, however if this is a commercial or residential project for a client and if you are attempting to comply with local, state, or national energy codes, or obtain LEED accreditation that you must utilize the maximum wattage as indicated on the label for your w/sq. ft. calculations.
 
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