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# Heat Treat Calculations

08/06/2017 12:54 PM

How do I calculate cost of heat treating process.?

Our oven runs on 480v.

Trying to recoup electricity used during this 5 hour process.

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#1

### Re: Heat treat calculations

08/06/2017 1:00 PM

amps * volts = watts - total watts times cost per kwh you are paying....

-example - 480 volts times 100 amps =48000 watts or 48kw using for 5 hrs = 240 kwh

cost per kwh est \$.10 = \$24 each 5 hr session

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#2

### Re: Heat treat calculations

08/06/2017 1:24 PM

Thank you SE.

Ill confirm our charges per kw.

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#6

### Re: Heat treat calculations

08/07/2017 3:38 AM

<...per kw...> Charges are actually more likely to be based upon the kWh.

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#7

### Re: Heat treat calculations

08/07/2017 8:48 AM

You do not get it. You need to provide information about the order of magnitude of the energy you need. You can either measure the current drawn by your oven (most accurate), or calculate it taking into account your thermal design (less accurate).

The price of the energy is important as well, but that depends mostly of your location. If I guess about 0.2\$/kWh I would not be too far, would I?

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#8

### Re: Heat treat calculations

08/07/2017 9:56 AM

That's why CR4 doesn't do <...cost...>: the price of electricity varies across the globe and the original post gives no clue as to where on the planet this installation is located, what the local electricity tariff looks like, nor the currency in which it is payable.

For that reason: <unsubscribes>.

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#11

### Re: Heat treat calculations

09/26/2017 12:02 PM

That must be "average" amps. In my (somewhat limited) experience the oven or furnace is on continuously till it reaches (near) set point temperature then cycles on and off (or if you have a more sophisticated one it cuts back to a lower rate) so you cannot use rating of furnace. If it is well insulated a 48kw furnace may average only 5 kw (on 1 minute, off 9, back on ...) holding temperature during the 5 hours so use only 25 kwh.

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#3

### Re: Heat treat calculations

08/06/2017 1:42 PM

Here are a few ideas that you've probably already thought of:

Your input energy goes to raise the temperature of your oven to operating temperature and maintaining that temperature due to heat loss.

The most important factor is using the best possible insulation to minimize the heat loss so that you use the least amount of energy maintaining your oven at the required temperature.

If you use batch processing, you only have to heat the workpiece, not the entire oven each time. The energy required is the mass of the workpiece times the heat capacity times the rise in temperature.

Converting heat back into low entropy energy (e.g., electricity) is limited by the Carnot efficiency, η = (TH - TC)/TH. If you calculate the amount of energy available from the temperature, mass, and heat capacity, you can determine if it is worth the trouble.

Finally, the cost of your energy will be less if you heat the oven with natural gas rather than electricity.

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#4

### Re: Heat Treat Calculations

08/06/2017 7:28 PM

The power used is what it is. Changing to High Efficiency Heaters - In Stock. Ships Today - uline.com‎ may help.

Using waste heat only makes sense if it saves more money than it costs.

Sometimes things just cost as much as they cost.

Be sure the oven is used at it's maximum efficient loading. Don't run it for only one piece, unless the cost is justified.

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#5

### Re: Heat Treat Calculations

08/07/2017 3:09 AM

CR4 doesn't do <...cost...>.

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#9

### Re: Heat Treat Calculations

08/07/2017 11:19 AM

You may also have to look at peak usage charges which will be higher.

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#10

### Re: Heat Treat Calculations

08/08/2017 12:49 PM

Don't forget to include initial heat up of the oven from room temp.

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