Panel Board Calculation

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bassil

Member
Can you please explain to me the following formula on a panel board (480VAC 3phase 3wire) drawings?


22465/277 = 81.10 + 25%(7.6) = 83.0 WSA

Thank you very much
 

ed downey

Senior Member
Location
Missouri
Re: Panel Board Calculation

Maybe They Are Looking At Individual Single Phase Loads And Not The Complete System 22,465 Watts / 277 V = 81.10 Amps Plus 25% For Continuous Load 7.60 Amps Total Of 87.70 Amps Single Phase.

I Don't Know Why They Are Doing This Though.
-Ed
 

rick5280

Senior Member
Re: Panel Board Calculation

Actually, this is the formula for figuring out how many Wrong Silly Answers one would get while figuring out just what the heck the figures mean!
In other words, you will get 83 WSA (wrong silly answers) before you give up trying to do this calculation.

On a serious note, is there any information ahead of the formula? It looks to me like the 22465 might be watts, 277 might be volts (22465/277 = 81.10amps?), but the 25% is throwing me. 25% of 7.6 is 1.90, and would make that part of the calc correct ( 81.10 + 1.90 = 83), but where did the 7.6 come from, and what the heck is WSA????

Rick Miell
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
Re: Panel Board Calculation

Originally posted by bassil: . . . formula on a panel board
Do you mean that you found this information written (perhaps by hand) on the face of a panelboard? If not, then where did it come from? Wherever it came from, it is nonsense.

Please note that the division of 22465 by 277 represents a single phase of the three phase system. If you are interested in, for example, checking on the size of the conductors to this panel, then a factor of the square root of three has to come into the equation at least two times.
 

lady sparks lover

Senior Member
Re: Panel Board Calculation

that's a strange one.

I would guess that:

22465/277 = 81.10 + 25%(7.6) = 83.0 WSA

22465 equals the watts or VA

277 equals the voltage

81.10 equals amps of all the other loads

7.6 is the maybe the amps of largest motor on the panel

25% is the 125% of the largest motor.

the sum of all the loads will give you the load of the panel.

Am I right?? :)
 

d and o

Member
Re: Panel Board Calculation

my third grade teacher took off points if you didn't "show your work". She would have used up two red pencils on that one.
 

bwyllie

Senior Member
Location
MA
Re: Panel Board Calculation

If it is on a drawing why not ask the person who drew it and get back to us and tell us what it is.
 

bonding jumper

Senior Member
Re: Panel Board Calculation

Yeah I remember this one from college, isn't this Kirchoff's second law, but I think he used the wrong value for G=9.81 not 7.6 and his units are incorrect it shouldn't be WSA, it should be Footpound furlongs.
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Re: Panel Board Calculation

bonding jumper:

I'm sure you ment Footpounds-furlongs per fortnight.

Steve
 
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