Panel load schedule

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jaehlee99

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I'm designing as beginner using a 120/208V panel schedule that shows the following loading:

Phase A: 439,304VA, Phase B: 364,136VA, Phase C: 370,820VA
Total: 1,174,260VA

So if I look at the total VA of 1,174,260VA does this mean that the panel has a load of 1,174,260/208/1.73 = 3,259A? I would then use this number as the load, and the minimum that the main breaker could be 1.25(Safety factor) x 3,259A = 4,074A? So, main breaker size would be AT=4200A, AF=4200 and AIC=5000. Is that correct?

Can anyone provide the good example AT/AF/AIC specification such as manufacturer? As each phase load do not draw evenly in the three phase system , in case, calculating the largest phase load to select 3P breaker size or wire size. Am I right?

Also, is there such a breaker size of 4,000A as a low voltage?

When calculating of wire size for this phase A load, 4,074A /10=407 A, then ten set of 600 kcmil was available for this phase leg.

I just wonder if this calculation is correct or realistic !! Otherwise, I highly appreciate if you provide your ideas to me.


Thanks
 
Phase A: 439,304VA = 3658 a Phase B: 364,136VA = 3033 A Phase C: 370,820VA = 3100 A Amps = load/120 volts

If you are going to add the 25% factor it should be 1.25(Safety factor) x 3658 A = 4,573 A

Using this figure, the 10 600 kcm would not be enough. You would neeed 11 sets. Thats a bunch.

Are these going to be in a duct bank?

Maybe someone has another suggestion.

Where did you AIC =5000 amps?
 
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Many thanks. Bob

Many thanks. Bob

Will big bunch of all cables be to place in a duck bank? Yes, it will.

Based upon your calculation, the current ampacity was 4573 A. I just wonder if the circuit breaker as low voltage will handle that current.

In terms of AIC, I posted it wrongly. AIC would be 42000.

I am looking for the appropriate catalog of AT/AF/AIC value.
 
jaehlee99 said:
I'm designing as beginner using a 120/208V panel schedule that shows the following loading:

Phase A: 439,304VA, Phase B: 364,136VA, Phase C: 370,820VA
Total: 1,174,260VA
Click to expand...

I think I would have started a beginning designer out with a somewhat simpler problem.

That is a substantial 208/120 system.
 
jaehlee99 said:
I'm designing as beginner using a 120/208V panel schedule...

I just wonder if this calculation is correct or realistic !!...
Click to expand...
Phase totals of a panel schedule do not reflect demand allowances, nor continuous vs. non-continuous loading. You should do an Article 220 calculation to determine [minimum] proper ocpd and supply conductor ratings.

The only thing panel schedule phase totals are good for is determining unbalance and how much to upsize ratings to cover the unbalance.
 
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jaehlee99 said:
... So, main breaker size would be AT=4200A, AF=4200 and AIC=5000. Is that correct?

...
Click to expand...
At that level of current, I doubt you will find a breaker with a 4200 frame. You probably only need a 4000AF breaker. I'm thinking next size up is 6000AF, but haven't looked to be certain.

Also, as Bob questioned, is your AIC of 5000. The AIC has nothing to do with your load calculation... directly. You need the available fault current value for the panel to determine the [minimum] AIC rating.
 
I doubt you will find a breaker with a 4200 frame. You probably only need a 4000AF breaker. I'm thinking next size up is 6000AF.
Click to expand...
After checkng the catalog, there is no AIC4200. Smart $ was right. To get the AIC for each breaker, fault current should be done the place where I am interested in. I heard that some programs is available such as SKM, ETAP. But the expense is very high to use at the office.
 
jaehlee99 said:
To get the AIC for each breaker, fault current should be done the place where I am interested in. I heard that some programs is available such as SKM, ETAP. But the expense is very high to use at the office.
Click to expand...

Do you have the transformer KVA rating, %Z and primary voltage?
 
With an infinite buss, the fault is 36 ka. If you assume a finite primary fault capacity, the fault is still in the 34 ka range. With a transformer that big at 208 volts, the fault is large.
 
If that's the transformer providing power to the 208Y/120V panel. You have a load issue. That transforner is only going to provide roughly 2080A.

Also, at that high of current rating most equipment is going to be rated for 100%, need to check specifcally wi the manufacturer selected.
 
With an infinite buss, the fault is 36 ka. If you assume a finite primary fault capacity, the fault is still in the 34 ka range.
Click to expand...

How did this number come out, for example using software? Would you explain about that ?

Many Thanks
 
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