NEC 220.86 School Calculations

[Sparky2791]

After completing the calculations per 220.86 what is the end result to be used for. The load to use to calculate the service size? It says 'the calculation of a feeder or service load.' So if that is the service load I can use that to determine the service size.

Lets say for example after doing the calculation the result is 1.5MVA and the service is 277/480V 3 phase Wye

1,500,000 / (480 * 1.73) = 1804A So this is the minimum service size? In other words a 2000A service is required.

Maybe I am over thinking this but thought I would get some opinions.

Thanks for the replies.

 

[ramsy]

Modern school rooms are built to trap heat like a green house, with commercial HVAC units dedicated to remove heat from each room.

Would be surprised if load is below 2000 Amps with all that HVAC bringing down power factor ~ 0.9

1,500,000 / 480 / 1.732 / 0.9 = 2,005

 

[ramsy]

Earth sheltered architecture, and natural ventilated buildings reduce HVAC requirements, but schools never caught on.

 

[david luchini]

So if that is the service load I can use that to determine the service size.

Yes

 

[steve66]

Yes

I agree for everything that is customer owned, but the utility gets to do what ever the heck they want.

Who hasn't done a service calculation and specified 600KCM service conductors, only to see the utility connect them to a 75 KVA xformer? (I may be exaggerating slightly, but not a lot.)