Load Calculation for School

[WELLSEROUSKI]

Help please,
I have estimated a connected load of 104,036 VA for this building.
The service is 120/208
Using 220.86 nec what do you guys come up with? Somehow Im doing something wrong.
Thanks

 

[daleuger]

Help please,
I have estimated a connected load of 104,036 VA for this building.
The service is 120/208
Using 220.86 nec what do you guys come up with? Somehow Im doing something wrong.
Thanks

A little more info please....

 

[Dennis Alwon]

Help please,
I have estimated a connected load of 104,036 VA for this building.
The service is 120/208
Using 220.86 nec what do you guys come up with? Somehow Im doing something wrong.
Thanks

If this is 3 phase system then you need to multiply your 208 X 1.73= 360. See if that helps

 

[mcclary's electrical]

not enough info to answer

 

[WELLSEROUSKI]

Building is 14,400 sqft.
3 phase service

 

[HEYDOG]

School Building

School Building

I did the calculation. I have a answer. But I woul like to see your calculation first.

 

[WELLSEROUSKI]

100% of first 3va/sq ft
3*14,400 = 43,200
plus
75% of the next
3*14,400 = 43,200 * .75= 32,400
plus
25% of of the next
3*14,400 = 43,200 * .25= 10,800 43,200+32,400+10,800=86,400va

86,400va / 208 = 415.38 amps

 

[Smart $]

100% of first 3va/sq ft
3*14,400 = 43,200
plus
75% of the next
3*14,400 = 43,200 * .75= 32,400
plus
25% of of the next
3*14,400 = 43,200 * .25= 10,800 43,200+32,400+10,800=86,400va

86,400va / 208 = 415.38 amps

Your still not giving us enough information. The above calculation appears to be load demand calculations of some sort, but you didn't state the type of building. The only 3-step load demand factoring which goes 100%-75%-25% is the optional method for school buildings. Is this correct?

 

[HEYDOG]

School Calculation

School Calculation

Here is what I got using 220.86 Optional Method

104,036 va / 14,400 square feet = 7.3 va per square foot.

First 3 va per sq. ft. @ 100% 3 va x 14,400 sq ft = 43,200 va

7.3 va per sq ft - 3 va we just calculated leaves 4.3 va per sq ft

4.3 va x 14,400 sq ft x 75% = 46,440 va

43,200 va + 46,440 va = 89,640 va / (208 x 1.732) = 249 amps
for a three phase system.

 

[Smart $]

Here is what I got using 220.86 Optional Method

104,036 va / 14,400 square feet = 7.3 va per square foot.

First 3 va per sq. ft. @ 100% 3 va x 14,400 sq ft = 43,200 va

7.3 va per sq ft - 3 va we just calculated leaves 4.3 va per sq ft

4.3 va x 14,400 sq ft x 75% = 46,440 va

43,200 va + 46,440 va = 89,640 va / (208 x 1.732) = 249 amps
for a three phase system.

That's not how 220.86 works. See below...

104,036 va / 14,400 square feet = 7.3 va per square foot. (copied from your post, not verified)​

The above qualifies for 75% demand.

104,036VA ? 75% = 78,027VA
78,027VA ? (3 ? 120V) = 217A​

Note 3 ? 120 = √3 ? 208

 

[HEYDOG]

School Calculation

School Calculation

I totally disagree with you. Reread table 220.86 first 3va per square foot @ 100%; next 17 va per sq ft @ 75% anything over 20va per sq ft @ 25%. This is the way that I have seen in Mike Holts Books and Tom Henry's and other well known Instructors. If this is wrong than someone needs to address it.
Not being a smart alec. Just making a statement.

 

[bob]

100% of first 3va/sq ft
3*14,400 = 43,200
plus
75% of the next
3*14,400 = 43,200 * .75= 32,400
plus
25% of of the next
3*14,400 = 43,200 * .25= 10,800 43,200+32,400+10,800=86,400va

86,400va / 208 = 415.38 amps

Assuming what you did is correct, you forgot the sqrt of 3.

86.4 kva/(.208 x 1.73)= 240 amps

 

[WELLSEROUSKI]

Allright..I think I understand now.
Thanks for your quick responses guys, feels good to know we can help each other.

 

[Smart $]

I totally disagree with you. Reread table 220.86 first 3va per square foot @ 100%; next 17 va per sq ft @ 75% anything over 20va per sq ft @ 25%. This is the way that I have seen in Mike Holts Books and Tom Henry's and other well known Instructors. If this is wrong than someone needs to address it.
Not being a smart alec. Just making a statement.

My bad... you are correct. I was looking at the imperial (ft) column only, where it does not say "First" and "plus"