question for the engineer

[steveng]

we recently opened a new science bldg, 2 1/2 story
the electrical service is a 3000 amp main, square d .
i was checking the main meter and thinking about all the kilowatts we have been consuming since the bldg came on line 4 weeks ago.

assuming we have been loaded at 800amps @ 480volts/ 3phase for 7 days 24hrs.


what would the kilowatt consumption be?:roll:

 

[jim dungar]

KWHR = V x A 1.73 x PF x HRs/Day x Days/Week x Week

KWHR = 480 X 800 x 1.73 x PF x 24 7 x 4

So what PF do you want to assume?

 

[steveng]

KWHR = V x A 1.73 x PF x HRs/Day x Days/Week x Week

KWHR = 480 X 800 x 1.73 x PF x 24 7 x 4

So what PF do you want to assume?

the digital meter on the panel read 809 amps,

assume .8

thanks boss:grin:

 

[steveng]

my calculator cant read that high.

i got 3.5713843, could that be anywhere close?

 

[bob]

the digital meter on the panel read 809 amps,

assume .8

thanks boss:grin:

Roll Tide? I'm not sure I want to try and answer this question.

KWHR = 480 X 800 x 1.73 x 0.8 x 24 x 7 x 4/1000 = 357138 KWHR

357138 KWHR x 0.08 Cents = $28571 . Better shut some of that off.

War Eagle

 

[72.5kv]

Don't forget to include the possible power factor hit. most utilities want it to be near the 90s.

 

[infinity]

Don't forget to include the possible power factor hit. most utilities want it to be near the 90s.

I think he did say a PF of .8.

assume .8

 

[jim dungar]

I am amazed that no one specifically pointed out that my formula was for watt/hr. I forgot to divide by 1000 to get to KWHR. MY BAD.

 

[dahualin]

Roll Tide? I'm not sure I want to try and answer this question.

KWHR = 480 X 800 x 1.73 x 0.8 x 24 x 7 x 4/1000 = 357138 KWHR

357138 KWHR x 0.08 Cents = $28571 . Better shut some of that off.

War Eagle

I don't think the current is 800amp during 24 hours. It varys during different period. So the electricity bill will tell you total KWH you consumed every month.

 

[rattus]

Roll Tide? I'm not sure I want to try and answer this question.

KWHR = 480 X 800 x 1.73 x 0.8 x 24 x 7 x 4/1000 = 357138 KWHR

357138 KWHR x 0.08 Cents = $28571 . Better shut some of that off.

War Eagle

You do mean 0.08 dollars which equals 8 cents?

 

[charlie b]

what would the kilowatt consumption be?:roll:

Some famous guy once said, "It (in this case, the question) doesn't say what you think it says."

The number of days and hours and weeks are not relevant. The kilowatt consumption is given by,

KW = V x A x 1.732 x pf / 1000,

KW = 480 x 809 x 1.732 x .8 / 1000,

KW = 538.

 

[bob]

I don't think the current is 800amp during 24 hours. It varys during different period. So the electricity bill will tell you total KWH you consumed every month.

Read the Post again. The poster said 24 hr 7 days a week.

 

[dahualin]

Read the Post again. The poster said 24 hr 7 days a week.

Bad assumption in that post.

 

[steveng]

you are right!

you are right!

Roll Tide? I'm not sure I want to try and answer this question.

KWHR = 480 X 800 x 1.73 x 0.8 x 24 x 7 x 4/1000 = 357138 KWHR

357138 KWHR x 0.08 Cents = $28571 . Better shut some of that off.

War Eagle

hey bob, lol were friends, it aint iron bowl yet?:grin:

yes , i have to admit i jumped the proverbial gun on this one, seems like i assumed to much on my assumption:grin:

at the time i read the meter we were at peak load, todays load was around 500amps, all this new gear is challenging to me to put it mildy. but, that's one reason why i am glad you guys are here on this forum.

the square d rep is coming down to set up anolgic display on the main panel.
the gc had the bldg running 24 /7 for approx 2- 3 weeks, all the hvac loads and were in hand. we have 2 300ton air cololed chillers / 1000amp brkrs

we also have an 8 bldg complex, the average bill is about
50k a month in summer, .

btw, i got the bas running now so we are saving some mula, .

 

[bob]

Some famous guy once said, "It (in this case, the question) doesn't say what you think it says."

The number of days and hours and weeks are not relevant. The kilowatt consumption is given by,

KW = V x A x 1.732 x pf / 1000,

KW = 480 x 809 x 1.732 x .8 / 1000,

KW = 538.

Charlie
I believe the OP wants Kilowatt Hours even if he stated kw.

 

[Psychojohn]

Why are you assuming a PF of 0.8?
Are there a lot of inductive loads?

I have a question about POCO electric meters, do they measure current and assume a constant voltage or do they actualy measure voltage and current to get KWh?

 

[iwire]

Voltage and Current.

 

[Psychojohn]

Then wouldn't you be charged as if the PF were 1?

 

[iwire]

Then wouldn't you be charged as if the PF were 1?

I don't understand why that would be.

Here is a cool site that can answer any question meter related.

The Meter Guy

 

[charlie b]

Charlie I believe the OP wants Kilowatt Hours even if he stated kw.

I am aware of that.

My comment was as much a request for the OP to clarify the question, as it was a suggestion that we all read the questions more carefully, especially if we are the ones posting the questions. :smile: