# Trying to calculate kilowatts per hour

Discussion in 'Homework Help' started by SoWatt, May 23, 2015.

1. ### SoWatt Thread Starter New Member

May 23, 2015
4
0
Hello,

As I indicated in my introductory message in the newb forum, I am woefully underinformed in this area, so please be patient and confine your mockery to a mild riot of abuse.

Problem: Trying to determine roughly how many kilowatts per hour are consumed by a Novatek Novair 1000 air filtration unit so that I can calculate the cost of running the machine continuously for a 24 hour period under local utility rates (here in Burbank, CA).

The specs listed on the machine itself are as follows (see pdf attached to this post for photo of specs posted on machine):
amps: 10
volts: 115
Hertz: 60

There are two settings:

Low = 600 CFM (cubic feet per minute)
High = 1000 CFM (cubic feet per minute)

I tried to figure it out myself using this online calculator: http://www.rapidtables.com/calc/electric/Amp_to_kW_Calculator.htm

But then the calculator asked for the "power factor," which I do not know.

I attempted to look that up and found this, which did not help me: http://www.allaboutcircuits.com/vol_2/chpt_11/3.html

So now I am trying to figure out the power factor so that I can calculate the kilowatts per hour.

But when I have done so, I still need to figure out how many kilowatts per hour the machine uses on the "Low" setting and on the "High" setting.

Any useful, constructive, direct answers will be greatly appreciated.

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2. ### paulktreg Distinguished Member

Jun 2, 2008
621
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3. ### SoWatt Thread Starter New Member

May 23, 2015
4
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Paul,

I will probably relent in my quest to figure it out for myself and buy just such a device.

4. ### SoWatt Thread Starter New Member

May 23, 2015
4
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I found this, but now I have to figure out whether “all the power is reactive power with no real power (usually inductive load)” or if “all the power is real power with no reactive power (resistive load).”

See below:

Power Factor

http://www.rapidtables.com/electric/Power_Factor.htm

In AC circuits, the power factor is the ratio of the real power that is used to do work and the apparent power that is supplied to the circuit.

The power factor can get values in the range from 0 to 1.

When all the power is reactive power with no real power (usually inductive load) - the power factor is 0.

When all the power is real power with no reactive power (resistive load) - the power factor is 1.

5. ### Ramussons Active Member

May 3, 2013
561
92
Contact the supplier and ask for the Power Factor rating.

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6. ### WBahn Moderator

Mar 31, 2012
18,079
4,917
First, some terminology and basic concepts. Kilowatts is a rate of energy consumption, so asking how many kilowatts per hour is largely meaningless. Think of it like this -- your car gets, so say miles per gallon (mpg), so would it make any sense to say that you were trying to find out how many mpg per hour your car gets?

The unit you are looking for is either how many kilowatts your unit draws when operating or, equivalently, how many kilowatt-hours per hour your unit consumes. A kilowatt-hour (kWh) is a measure of energy, namely the amount of energy consumed by something drawing 1 kW of power over the course of 1 hour.

The label values (the 10A) doesn't tell you how much the unit actually draws, but rather what the maximum amount it should ever draw. So using 10A will give you an upper limit on what it will consume. At 115 V and 10A, that would be 1.15 kW and if pulling that for 24 hours it would be about 28 kWh. In practice, particularly on the low setting, it will draw significantly less than that, perhaps 50% of that. Multiply that by your utility rate and you'll get your cost. If your rate is 18 cents/kWh then you would be looking at a max of about \$5/day and probably something closer to \$2 to \$3 per day.

7. ### SoWatt Thread Starter New Member

May 23, 2015
4
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I did that after I posted my question here.

So perhaps I will get an answer that way.