Service calc for motors

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mmasic

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I have a problem to prove that my service is working. we have a building with one 2000A MCC and some small lighting loads (four lamps and two receptacles). Electrical inspector is looking for calculation step by step with reference to NEC. He is talking about 125% for continuous load (lighting) and 100% for noncontinuous loads. It looks to me that service shall be based on connected load?? How to prove demand and diversity factor???
Thanks
 
Re: Service calc for motors

He is talking about 125% for continuous load (lighting) and 100% for noncontinuous loads
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He is correct. You caculations should come from section 220 of the NEC. This section give you factors to apply to the loads. The NEC does not give much help on commercial and industrial loads. Its the designer that must provide the info as to what the max demand will be.

[ February 24, 2006, 11:02 AM: Message edited by: bob ]
 
Re: Service calc for motors

I know but problem is I can not prove by code that I can use some demand factor less that 100%.. And everybody knows that all motors are not working at the same time.
 
Re: Service calc for motors

Originally posted by mmasic:
I know but problem is I can not prove by code that I can use some demand factor less that 100%.. And everybody knows that all motors are not working at the same time.
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If you can show the motors can not run at the same time you can use 220.60 about noncoincident loads.
 
Re: Service calc for motors

Originally posted by mmasic:. . . but problem is I can not prove by code that I can use some demand factor less that 100%.
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Do you need to? It is certainly permissible to size a service on the basis of total connected load, with no demand factors applied. It is only when you want to save money on the installation (i.e., by sizing the service smaller than needed for the total connected load) that the NEC allows you to apply certain demand factors.

Is this a new facility or a modification to an existing facility.
 
Re: Service calc for motors

You can always go and design service for connected load but that is just not right. That means that everything will be oversized.. I tried to find in NEC diversity factor but I found just table 430.22.E for Duty cycle service..
Thanks
 
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