Kw to kva

[hhsting]

I was told by engineer that NEC 2017 Article 220.5 is about turning kw to kva. It requires turning kw to kva. Can anyone here explain to me how this is so? I dont see it in the code itself

 

[Dsg319]

KVA is the apparent power as KW represents real usable power.

I’m lost at what he is saying though.

 

[ron]

220.5 provides guidance regarding calculations and how to deal with nominal system voltages and rounding to the nearest whole ampere.
Calculations for breakers and conductors are typically done with volts and amps, and does not take power factor into account, which would be needed for watts.

 

[LarryFine]

It requires turning kw to kva. Can anyone here explain to me how this is so?

Are you asking what the difference is, or why it's necessary to do?

 

[hhsting]

Are you asking what the difference is, or why it's necessary to do?

I am asking does the NEC 2017 Article 220.5 require turning kw to kva? Is it in the NEC 2017 Article 220.5? I am asking because i have plans that say per NEC 2017 Article 220.5 engineer has converted kw to kva. I just don’t see how NEC 2017 Article 220.5 would do that?

 

[LarryFine]

Lemme look.

Nope, I don't see it.

I would omit the first half of the sentence and merely say, "(The) engineer has converted kw to kva."

 

[hhsting]

Lemme look.

Nope, I don't see it.

I would omit the first half of the sentence and merely say, "(The) engineer has converted kw to kva."

Ah thanks

I think the engineer is looking at the blue text in NEC 2017 handbook Article 250.5.


I just dont see where it says blue text is enforceable or not?

 

[LarryFine]

I just dont see where it says blue text is enforceable or not?

If it's not in the NEC, it's not code.

 

[hhsting]

If it's not in the NEC, it's not code.

I know but it must say in handbook blue text not part of code? Apparently engineer keeps on insisting it is

 

[TX+ MASTER#4544]

2023 NEC Regarding kVA and watts and VA (volt amperes.)

Look at sections 220.54 and 220.55.
Look at all of the calculations found in Annex D of your Code book.
Notice the usage of VA for their calculations.
And then using Ohm's Law converts it to A (amps.)

Thanks for reading.
Comments accepted.
TX+MASTER#4544

 

[baserunner4]

Article 220.5 in the 2017 NEC (what I'm currently up to date on) outlines the calculations for branch-circuit, feeder, and service loads, specifically defining how loads are calculated based on the type of load. While this section does not explicitly mention "converting kW to kVA," it deals with the calculation of demand loads, which often involves considering the power factor.

The relationship between kW (real power) and kVA (apparent power) is: kVA=kW/Power Factor

In practical terms, when calculating load, particularly for non-linear or inductive loads, the NEC requires you to use the apparent power (kVA) rather than just the real power (kW) because the power factor affects the current drawn by the equipment. This is implied rather than directly stated.

 

[Speedskater]

note that "k" is always lower case
and "A", "V" and "W" are upper case.

 

[Besoeker3]

I was told by engineer that NEC 2017 Article 220.5 is about turning kw to kva. It requires turning kw to kva. Can anyone here explain to me how this is so? I dont see it in the code itself

You can't - they are different units. And a wee correction - kW and kVA if you don't mind.

 

[charlie b]

Unless you are willing to risk unknowingly getting an incorrect result from your calculations, you should always do things in the following order:

1. Convert all loads to kva.
2. Add all loads to get a total KVA.
3. Convert the result from Kva to amps.

You can always add KvA to kVA and get a correct answer in kVa. You can't always add Amps to amps and get a correct answer in AMPS. The risk of getting an incorrect answer is greatest when you are adding single-phase loads (single pole and/or two pole) to three-phase loads.

 

[charlie b]

Why don't we just skip the whole capitalization issue and call it what it really is:

Thousand Kilogram-Meter Squared per Second Cubed!​

​

 

[eric stromberg]

I'm going to speculate as to what he meant. It seems like more of a philosophical statement. There are many loads. Some resistive, some reactive. Regardless of how the loads affect the power delivery system, at the end of the day, the system has to be connected to the utility and the utility has to provide the right amount of power to allow the system to work. I don't, however, see this as the purview of Art. 220.

 

[Besoeker3]

Why don't we just skip the whole capitalization issue and call it what it really is:

Thousand Kilogram-Meter Squared per Second Cubed!​

​

Hi Charlie b!
You know I'm just an old British plonker but I do prefer to use correct units including electrical units. This probably stems from my student days. One of my tutors gave one of my marks incorrectly - Amps instead of A otherwise it was 100%. Unreasonable but didn't do it again.

 

[charlie b]

I am OK with the notion of, "What's so wrong about being right?" But if I were to point out every language error (e.g., spelling, punctuation, capitalization, word selection, grammar, etc.) made by any and all forum members, they would start calling me worse things than "plonker." They might even stop participating for fear of getting publicly corrected and because participating had become less enjoyable.

What say we focus on the technical stuff?

 

[tallgirl]

I'm going to speculate as to what he meant. It seems like more of a philosophical statement. There are many loads. Some resistive, some reactive. Regardless of how the loads affect the power delivery system, at the end of the day, the system has to be connected to the utility and the utility has to provide the right amount of power to allow the system to work. I don't, however, see this as the purview of Art. 220.

Sounds about right, especially the comment about some loads being resistive, and some being reactive, and some loads are just real turds and will consume more amps if the voltage is lower, which isn't how resistive loads work.

 

[TX+ MASTER#4544]

2023 NEC
tallgirl

Don't worry about resistance, reactive, power factor "and some loads are just turds."

Use volt amperes and not watts V X A volts times amps and include the 1.732 if it's 3 phase.

Look at Informative Annex D Selection of Conductors. And all of the examples found therein Annex D.
They are expressed in volt-amperes, V x A and 1.732 for 3 phase then use Ohms Law to change to amps so you can size your wires, select panels size in amps, circuit breakers and any thing else expressed in amperes.

And, you can use watts as indicated in Sections 220.55 and 220.54.

By using volt amperes your calculated load will be a little more had you calculated watts....because you don't know what the power factor is.
So, you can't go wrong if you use VA cause it will be the larger of the two, iest,.VA vs Watts.

Thanks for reading.
Comments accepted.
TX+MASTER#4544