Industrial Load Calculation

[Bill Butterfield]

I am trying to figure out the load calculations so that I can size the feeding transformer as well as the conductors feeding the new switchboard. The service is 480 3 phase 4 wire, I have 67 fixture at 2 amps each, 50 outlets (1) 125 hp motor, (1) 75 hp motor, (4) 25 hp motors,(3) 20 hp motors, (1) 10 hp motor,(5) 5 hp motors and (6) ovens that draw 290 amps each. can someone give me a hand?

 

[cpal]

describe the building use and attempt the feeder demand from article 220. let us know where you are in the NEC and what you are getting for numbers. Some one will be happy to help

 

[benaround]

Bill,

I would recomend getting an E.E. involved, there is more to consider than just the load

calc., and if you are unsure about it the E.E. will know what to do.

 

[kingpb]

I am trying to figure out the load calculations so that I can size the feeding transformer as well as the conductors feeding the new switchboard. The service is 480 3 phase 4 wire, I have 67 fixture at 2 amps each, 50 outlets (1) 125 hp motor, (1) 75 hp motor, (4) 25 hp motors,(3) 20 hp motors, (1) 10 hp motor,(5) 5 hp motors and (6) ovens that draw 290 amps each. can someone give me a hand?

What is the voltage of the fixtures, i.e. 480V 1-ph, or 277V 1-ph
What is voltage of outlets, and what are they used for, i.e. specific machines, or general use?
Are motors 3-ph?
and are Ovens 3-ph?

 

[kingpb]

Based on one heck of a lot of assumptions, since not much info to go buy....

My estimate is 2000KVA transformer, and it will be about 2400A 480Y/277V service. So your looking at a 3000A frame breaker.

Nice little service..........

 

[Bill Butterfield]

Industrial load calculations

Industrial load calculations

The lighting is 277 v, the outlets are 120v all motors and ovens are 3 phase. the motors are used in the process of making beef jerky so motors are intermitent

 

[kingpb]

The lighting is 277 v, the outlets are 120v all motors and ovens are 3 phase. the motors are used in the process of making beef jerky so motors are intermitent

Your still looking at a service capable of around 2000KVA.

By studying the load profile, there might be some opportunity to squeeze it down to a 2000A service but your standard transformers are 1500KVA (1800A) and 2000KVA, especially since you say you have intermittent motor loads. The heavy consumers are the ovens, and if they aren't going to be used at the same time, then there may be some additional diversity that can be applied. It may be tough to get down to 1800A, if that's the case then you might as well beef it up (no pun intended, well maybe a little) and go with the full 2400A (2000KVA) capability.

Keep in mind that as you fine tune the load profile, you may also be taking out any expansion capability with it. Owner needs to decide if expansion is a possibility for the facility.