Calc and transformer questions

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highlakeselectric

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Maximum primary overcurrent protection allowed for a 2.8 impedence 500 kva 408 208/120 3 phase transformer?
700
1500
1200
2000

Industrial plant office 150x150 with 120 volt lighting 300 general purpose receptacles service is 120 208 3 phase ?
307
501
362
351
Thanks for anyone giving me a hand!!



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Smart $

Smart $

Esteemed Member
Location
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Seems like class assignment or test questions...

What are your answers and why?

We'll weigh in once you provide the above.
 
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highlakeselectric

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Supervisors test questions these are easier than the other thread i posted some of the test questions confused me on how and when to reduce receptacle loads because of the way they were listed and the answers provided


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highlakeselectric

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Location
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Ind plant office
150x150 22500x3.5=78750
78750x125%=98437.5
300 receptsx180=54000
First 10 kva@100%. 10000
Remainder 44000@50% 22000
Total 32000
98438va
32000va
130438x(208x1.732)
130438/360.256
362
Everyone agree? Im sure i missed something


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Smart $

Smart $

Esteemed Member
Location
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highlakeselectric said:
Ind plant office
150x150 22500x3.5=78750
78750x125%=98437.5
300 receptsx180=54000
First 10 kva@100%. 10000
Remainder 44000@50% 22000
Total 32000
98438va
32000va
130438x(208x1.732)
130438/360.256
362
Everyone agree? Im sure i missed something


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Didn't check the ampere calc' but everything looks good to me.

BTW, 208V x sqrt(3) is exactly 360.
208V is a rounded value of 120V x sqrt(3).
 
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highlakeselectric

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Location
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Im not understanding because they dont specify if i have primary and secondary prot.. I can assume they would but that was how they worded it


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highlakeselectric

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Location
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Check my other post smart$ and see what you think about recetacle demands i could not get any one of the answers for that calc i tried it so many ways with a sign without .. Thanks again for your help


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Smart $

Smart $

Esteemed Member
Location
Ohio
highlakeselectric said:
601.42x2.5 ? 1503 or 601.42x1.25 751.775


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highlakeselectric said:
Im not understanding because they dont specify if i have primary and secondary prot.. I can assume they would but that was how they worded it


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Protection is based on xfmr rated current.

The max pri ocpd rating is when you have secondary protection.
 
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