# How much energy is used by a 1,500w heater

Discussion in 'Homework Help' started by bwd111, Jul 27, 2013.

1. ### bwd111 Thread Starter Member

Jul 24, 2013
117
1
that runs non stop for 8 hours

2. ### blueroomelectronics AAC Fanatic!

Jul 22, 2007
1,758
98
1500 x 8 = 12kW

bwd111 likes this.

Jul 18, 2013
10,826
2,495
12Kw-Hours.
Max.

4. ### DerStrom8 Well-Known Member

Feb 20, 2011
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1,329
You must first define what kind of "energy" you're referring to. If you're referring to "power", then it is as Bill (blueroomelectronics) said. However, energy can also be in the form of heat, light, etc. I can only assume in this case you mean power though, but you should be more careful about your terminology.

Regards,
Matt

5. ### DerStrom8 Well-Known Member

Feb 20, 2011
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Oops, good catch.

6. ### bwd111 Thread Starter Member

Jul 24, 2013
117
1
How about this one 25kw heater operating across three phase 460v what is the current draw?

I got 54.35

7. ### DerStrom8 Well-Known Member

Feb 20, 2011
2,428
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I just realized this post was in the "homework help" forum. You should have done the math for the first one yourself instead of having the answer given to you.

Anyway, 25kw is the power, you have the voltage, and you're looking for current. P = I*V, so 25,000W = I * 460v.

You are correct, that gives you 54.35 AMPS (watch your units!)

Matt

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8. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
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I think that last answer is incorrect for s 3phase system.

9. ### bwd111 Thread Starter Member

Jul 24, 2013
117
1
I did do the math 5 times and got 54.35 using the same formula P=I*V 54.35 now Im seeing other use a different formula and getting 31.41 and wanting to know why they are getting this.

10. ### bwd111 Thread Starter Member

Jul 24, 2013
117
1
Do you agree I should of used √3 formula?

11. ### bountyhunter Well-Known Member

Sep 7, 2009
2,498
507
It also depends on the power factor.

12. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
The 3-phase load is 25kW.

How many kW per phase?

Did you quote the line-to-line or line-to-neutral voltage?