I need help with a complex calculation

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Huntxtrm

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I need to do a calculation from head to tail on an industrial service. Is that something I could post here to make sure that I am stepping it out right? If so, tell me. I will post all the specs. Thanks
 
Huntxtrm said:
I need to do a calculation from head to tail on an industrial service. Is that something I could post here to make sure that I am stepping it out right? If so, tell me. I will post all the specs. Thanks
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Absolutely

Roger
 
Ok, don't beat me up to bad. This is complex for me. Im looking into getting some learning material for doing all calculations. Any recomedations on that would be appreciated as well.

Specifics that are known:
  • 50,000sqft warehouse
  • 1,000 office within warehouse
  • No HVAC
  • Receptacle count Unknown
  • 10 hp pump 460v 14.2 amps (Name Plate)
  • 10 hp pump 460V 11.5 amps (Name Plate)
  • 5 hp compressor 460v
  • 28 hp pump 460 v 35 amps (Name Plate)
  • 100 hp compressor 460v 180 amps (Name Plate)
  • 100 hp back up compressor 460v (non coincidal with above)
  • Blower 460v 78amps (Name Plate)
  • Vacuum 460v 50amps (Name Plate)
  • Control compressor 460v 5hp
  • Waste Blower 5hp 5.72amps (name Plate), 460v
  • Dryer 110v 1amp
  • Tank 110v 1 amp
  • Filter 110v 1 amp
  • Dryer 110v 1 amp
  • 120v 20amp circuit for computer
  • 120v 20amp circuit for Scale monitors
  • 120v 20amp circuit for LV power supply
None of the motors are continuous.
 
lighting load:

warehouse 49,000sqft x .25 = 12250 va (from table 220.12) x 1.25 for continuous = 15312 va 1st 12500 @ 100%, 50% there after (Table 220.42) = 12500 +(2812.5 *. .5) = 13906.25 va

Office 1000 sqft x 3.5 = 3500 va (from table 220.12) x 1.25 for continuous = 4375 va

Receptacle Load:

Office 1,000 sqft x 1va = 1000va (220.14k2) 1st 10 kva @ 100%(Table 220.14) x 1.25 for continuous = 1250 va
Motor Loads:

1. 10 hp pump 460v x 14.2A x 1.732 = 11,313 va non-continuous

2. 10 hp pump 460v x 11.5A x 1.732 = 9162 va non-continuous

3. 5 hp compressor 460v x 7.6A(table 430.250) x 1.732 = 6055 va non-continuous

4. 28 hp pump 460v x 35A x 1.732 = 27885 va non-continuous

5. 100 hp compressor 460v x 180A x 1.732 = 143410 va x 1.25 (430.24) = 179,263 vanon-continuous

6. 100 hp backup compressor 460v x 124A(table 430.250) x 1.732 = 98,793 va non-continuous, noncoincidal with above, smaller of the 2 dont count(220.60)

That is not all, Im pulled away from my desk! To be continued. Feel free to pick me over so far. Thanks
 
I'm back!

7. Blower 460v x 78A x 1.732 = 62,144va non continuous
8. Vacuum 460v x 50a x 1.732 = 39,836va non continuous
9. Waste Blower 460v x 5.72A(name Plate) x 1.732 = 4,557va non continuous
10. 5 hp Compressor 460v x 7.6a(Table 430.250) x 1.732 = 6055va non continuous11. Desicant Dryer 110v x 1A = 110va x 1.25 continuous = 138va
12. Manchester Tank 110v x 1A = 110va x 1.25 continuous = 138va
13. Oil filter 110v x 1A = 110va x1.25 continuous = 138va
14. Refrigerant Dryer 110v x 1A = 110va x 1.25 continous = 138va
15. Computer circuit 120V x 20 amp x 1.25 continuous = 3000va
16. PLC power supply 120V x 20 amp x 1.25 continuous = 3000va
17. Scale Monitor Circuit 120V x 20 amp x 1.25 continuous = 3000va
 
Which equals 474004.25 VA
or 474kva.

474004/(480 x 1.732) = 570 amps
So I would need an 800 amp rated panel board 480v
Main breaker size @ 600 amp

Please check my math and method on this. I will move to tranny sizing after this. So ask any questions you wish. And by all means, correct me if necessary! I havent done this in a while, and I am moving into the design of these systems. So i need to brush up, and or learn the things, I dont know.

A few questions of my own:
1. Should I calculate my 120/208 load based on Panel size and transformer sized to panel? Or to the actual loads? Transformer seems right to me, but i cant' find it in section 220?

And Thanks For any help. It will be greatly appreciated.
2.
 
Another question.
When calculating motor loads, I should always use nameplate FLA when available. Correct? And 430.250 When not available?
 
Is the Mike Holt book "Electrical formulas with sample calculations". A good calc book, that covers all aspects of electrical calcs? End to end calcs?
 
Huntxtrm said:
Another question.
When calculating motor loads, I should always use nameplate FLA when available. Correct? And 430.250 When not available?
Click to expand...
Generally incorrect. See 430.6.

Also, you have to calculate the largest motor at 125%. See 430.24.
 
Huntxtrm said:
...
11. Desicant Dryer 110v x 1A = 110va x 1.25 continuous = 138va
12. Manchester Tank 110v x 1A = 110va x 1.25 continuous = 138va
13. Oil filter 110v x 1A = 110va x1.25 continuous = 138va
14. Refrigerant Dryer 110v x 1A = 110va x 1.25 continous = 138va
15. Computer circuit 120V x 20 amp x 1.25 continuous = 3000va
16. PLC power supply 120V x 20 amp x 1.25 continuous = 3000va
17. Scale Monitor Circuit 120V x 20 amp x 1.25 continuous = 3000va
Click to expand...
Generally speaking, 11 through 14, if supplied by receptacle would be calculated in with receptacles. Receptacles cannot be calculated at less than 180VA per yoke.

15 through 18 appear odd. Is the 20A value a loading value or the circuits' ampacity? If allowing for full loading of a receptacle circuit, you'd just use 20A (16A continuous)... and if using multiple receptacles on the circuit, you must also not be below 180VA per yoke. Also, 20A for a PLC power supply and Scale Monitor Circuit seem high.
 
chris kennedy said:
They sure can and I often do when I submit as-builts.

220.14(A).
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Well for that we're getting into interpretations, where opinions vary. First, 220.14(A) says outlet, not receptacle. Then it goes on to say for a specific appliance or other load not covered in 220.14(B) through (L)... and receptacle outlets ARE covered in (I) through (K).

I'm not saying you are incorrect... just my belief it's not generally viewed or calculated that way.
 
I got a PM from a respected member here that agrees with you, yet I will tell you the EE's and BO's here don't have a problem with me using that for rec's. Most notably I did a couple schools here (2 different counties) that had hundreds of work stations under 50 watts and my as-builts went through the EE and were approved by the bldg depts, go figure.;)
 
chris kennedy said:
I got a PM from a respected member here that agrees with you, yet I will tell you the EE's and BO's here don't have a problem with me using that for rec's. Most notably I did a couple schools here (2 different counties) that had hundreds of work stations under 50 watts and my as-builts went through the EE and were approved by the bldg depts, go figure.;)
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I completely understand some willingly accept the practice...

But just to add a little more rationale to the matter, 220.14(L) regards outlets other than covered in (A) through (K)... which amounts to outlets with no load. Seems contradictory these are required to be calculated at 180VA per if an outlet with less than 180VA is allowed to be calculated at face value.
 
Smart $ said:
Generally speaking, 11 through 14, if supplied by receptacle would be calculated in with receptacles. Receptacles cannot be calculated at less than 180VA per yoke. They are receptacles. So just use 180va. like all receptacles, Then multiply by 1.25 for continous?

15 through 18 appear odd. Is the 20A value a loading value or the circuits' ampacity? If allowing for full loading of a receptacle circuit, you'd just use 20A (16A continuous)... and if using multiple receptacles on the circuit, you must also not be below 180VA per yoke. Also, 20A for a PLC power supply and Scale Monitor Circuit seem high.
Click to expand...
I understand what you are saying, I was just calculating for a 20 amp 120 volt circuit feeding them, as the true load is not known. And it is a dedicated circuit. Which, I am taking is wrong. I need to derate the 20 amp circuit for continuous loading? Is this what you are saying?
 
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