designer

[bggn]

I am designing 12 story apartment building. Aftercalculating each apartment load, and each floor load (26 apartments per floor),I applied diversity factor and came up with 370 amp demand load. Do I have to multiply360 by 1.25 for circuit breaker size (and provide 500 amp c.b.) or can Iprovide 400 amp c.b.?

Thanks in advance.

 

[jumper]

Annex D has good examples of similar calculations.

 

[jrohe]

I am designing 12 story apartment building. Aftercalculating each apartment load, and each floor load (26 apartments per floor),I applied diversity factor and came up with 370 amp demand load. Do I have to multiply360 by 1.25 for circuit breaker size (and provide 500 amp c.b.) or can Iprovide 400 amp c.b.?

Thanks in advance.

Something is not right. A 370 amp demand load for a total of 312 apartment units is impossible. A 370 amp demand load even for 26 units, if you were talking on a per-floor basis, seems very low.

 

[Npstewart]

You have to be extremely careful on how and when you apply the demand factor. You apply the demand factor to size the service only, and this should be done using the total load of the apartments (ie. before those huge 40% deductions). Read the NEC carefully for this and use the Annex D as suggested for good examples.

 

[malachi constant]

I am designing 12 story apartment building. Aftercalculating each apartment load, and each floor load (26 apartments per floor),I applied diversity factor and came up with 370 amp demand load. Do I have to multiply360 by 1.25 for circuit breaker size (and provide 500 amp c.b.) or can Iprovide 400 amp c.b.?

Thanks in advance.

You seem pretty unsteady navigating this part of the code. Can you walk us through which sections you used for calculating individual apartment loads, each floor loads, etc? I've done dozens of these, and have seen a lot of mistakes over the years. I'm happy to answer any questions if you want to get more specific.

To answer your question, assuming you properly arrived at a 370A load for each floor, you can size your breaker to that. You typically only multiply 1.25 to continuous loads such as lighting or electric heat, or for largest motors. The 370A is good as-is, a 400A breaker would meet code...assuming the rest of your calcs do. 370A sounds very low for a floor with 26 units. I would guess the loads to be three times that at least. Again, if you want to show your work I'm happy to critique it. I suspect you are off somewhere.

 

[bggn]

Thank you for your answer. Load of 370 amperes basically an imaginaryload. What I wanted to find out whether apartmentloads consider being a continuous loads.

Thank you again.