Calculating the kva load of mechanical equipment

[JoeStillman]

OK, my next question is related to the blower unit - all I have there is hp (=1) and voltage (=480/3P). I believe the NEC table for 3 phase motors shows the FLA to be 2.1 (@460V). So to get the 3 phase kVA for that equipment I simply multiply (2.1)*(480)*SqRt(3)/1000 to get 1.745 kVA? Is that correct?

You are correct.

Don't get sucked into a debate about whether to use the nominal voltage (460) or the system voltage (480) for this calculation. Whatever voltage you use is wrong. The utility is allowed to swing from 85% to 110% of "Nominal." And "Nominal" is whatever they say it is. I've seen one utility use 480 and another use 460. And it WILL swing, usually lower in the summer and higher in the winter. Then don't forget about your feeder and branch circuit voltage drops. When it comes to load calcs, this stuff falls under the heading of "How many angels fit on a pin-head".

Just remember; S = I x E x 1.73 and don't bite your fingernails.

 

[Iron_Ben]

You are correct.

Don't get sucked into a debate about whether to use the nominal voltage (460) or the system voltage (480) for this calculation. Whatever voltage you use is wrong. The utility is allowed to swing from 85% to 110% of "Nominal." And "Nominal" is whatever they say it is. I've seen one utility use 480 and another use 460. And it WILL swing, usually lower in the summer and higher in the winter. Then don't forget about your feeder and branch circuit voltage drops. When it comes to load calcs, this stuff falls under the heading of "How many angels fit on a pin-head".

Just remember; S = I x E x 1.73 and don't bite your fingernails.

Sorry, but got to disagree about the allowable voltage swing. ANSI C84.1 is the standard that U.S. utilities are held to. In a nutshell, with a few minor exceptions that seldom come into play, it's simply this: +/- 5% of nominal. So at your house, the utility must supply voltage within a range of 114-126 and 228-252. For a 480Y/277 service, it's 456-504. And so on. Yes, a utility's primary voltages are dynamic rather than static, but regulation is used to keep things within that 10% bandwidth.

Ben

 

[jumper]

The full load amps (or running load amps) includes the effect of both resistive and reactive loads. Multiplying the volts times the RLA times the square root of 3, then dividing by 1000, gives you KVA, not KW.

Whether to use the value 460 or 480 for the voltage is a matter of some debate.

Thank you.

 

[jumper]

View attachment 11220

Hello Jumper,

This image can help you. You can not deny from power factor, it has any value between 1 to 0 or even 1 and 0.
this screenshot may help you.

Thanks HE. How have you been?

 

[Hameedulla-Ekhlas]

Thanks HE. How have you been?

thank you Jumper for asking. After years just took a look this wonderful forum. was busy in my own network www.zone4info.com. Just developed a small engineering network too. when I find time, I will regularly check with you guys. Are those people here who were 4 years ago?

 

[jumper]

Are those people here who were 4 years ago?

Yeah, all the usual troublemakers like me are still here.

We even picked some new ones.

 

[Hameedulla-Ekhlas]

Yeah, all the usual troublemakers like me are still here.

Troubleshooter or troublemaker?. you all are great.