Please check my homework

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Michael15956

Senior Member
Location
NE Ohio
Commercial Install
Existing Supply: 208Y/120
Each Phase Fused at 150A

Continuous Lighting Load taken at 120V= 8,250VA
General Purpose Receptacles @ 180VA= 8,280VA
Dedicated 3 Phase Loads= 25,600VA
Existing 3 Phase Air Conditioning load= 10,400VA
30A Heating (Omitted)

Total Load : 52,530VA

52,530VA/(208 x 1.732)=146Amps.
 
Last edited:
e57 said:
Demand factor or continuous/non-continuous loads???? Lighting by occupancy sq' - or was it totaled from fixtures?
Click to expand...
e57,

No demand factor for receptacles, under 10kVA.
Continuous lighting load already figured in lighting load, including outside sign.
Lighting is not by sq. ft. at this time. I get to that later. Lighting is actual load.
 
Please, Pardon My Dear Aunt Sally.

P= parthesis
M= Mutiply
D= Divide
A= Add
S= Subtact

Order of Operation and I failed...

You had me going with last equation.
You stated A/BxC when its in fact A/(BxC) (Like it mattered)...
I had to check the Annex D :rolleyes:

There is Branch Service but no Term of "Dedicated Service" nfpa-70 05'.
 
Easy Check:

Easy Check:

Michael15956 said:
Commercial Install
Existing Supply: 208Y/120
Each Phase Fused at 150A

Continuous Lighting Load taken at 120V= 8,250VA
General Purpose Receptacles @ 180VA= 8,280VA
Dedicated 3 Phase Loads= 25,600VA
Existing 3 Phase Air Conditioning load= 10,400VA
30A Heating (Omitted)

Total Load : 52,530VA

52,530VA/(208 x 1.732)=146Amps.
Click to expand...

An easy check on your calculation is to assume that each phase delivers 17.5kVA @ 120V, then,

Iline = 17.5KVA/120V = 146A

No sqrt(3) needed.
 
rattus said:
An easy check on your calculation is to assume that each phase delivers 17.5kVA @ 120V, then,

Iline = 17.5KVA/120V = 146A

No sqrt(3) needed.
Click to expand...

And this from the guy who likes to show us how complicated electrical calculations are! ;)
 
Aw Contrary Larry:

Aw Contrary Larry:

LarryFine said:
And this from the guy who likes to show us how complicated electrical calculations are! ;)
Click to expand...

Not so Larry. Some calculations are complicated, but my motto is:

K.I.S.S.

Or "Keep It Simple Stupid".

Or "Keep It Simple Rattus".
 
Michael15956 said:
e57,

No demand factor for receptacles, under 10kVA.
Continuous lighting load already figured in lighting load, including outside sign.
Lighting is not by sq. ft. at this time. I get to that later. Lighting is actual load.
Click to expand...
Reason I asked is we don't know what this building is - schools, farms and resturaunts aslo can have demand factor applied... "Dedicated 3 phase loads" could be anything....
 
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