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110v/220v Oven calculator
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jegner
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PostPosted: Wed May 10, 2006 5:58 am    Post subject: 110v/220v Oven calculator Reply with quote

For all your 110 to 240v oven wattage and amps calculations:


http://www.tk560.com/ovencalculations.html

A special thanks to Peter Botha for taking the time to make this awesome page.

Enter your voltage, size of your oven base, and find out all the details! It even generates the wiring layout diagram!

Jim


Last edited by jegner on Tue Feb 23, 2010 11:33 am; edited 2 times in total
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AlterEgos
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PostPosted: Sat Jun 10, 2006 8:47 pm    Post subject: Reply with quote

SWEET!!! You guys ROCK!!!

I will definitely be using that page when I build my next vac oven, since I'd like a larger one to work with. Very Happy
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knightshade
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PostPosted: Tue Jun 27, 2006 1:08 pm    Post subject: Reply with quote

I would be happy to discuss things more in depth - but I believe that there is a false assumption for the total resistance between live and neutral when dealing with a 220v oven.

I believe that in a four segment oven - one will find that the desired "total" resistance between live and neutral is in fact 5.042 reguardless to the oven running on 220v or 110v. With 220v the resistance between a single live line and neutral should be 10.084 - and that would be the number that I would expect to see listed in the row "Total Resistance"


Correcting such a figure will have impact on the conclusion drawn.
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knightshade
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PostPosted: Tue Jun 27, 2006 1:41 pm    Post subject: Reply with quote

In looking at it in more depth, I believe that the issue lies in how the variable "restot" is calculated.

Code:
var restot = volts/amps;


While I understand where this equation came from a formula perspective - one must also consider the fact that 220v electric runs two live lines running from the device to the electrical panel. As these are in parallel, this cuts the total resistance over each line in half.

I'm sure that someone with more of a background in electricity could comment more authoritatively.


As an aside - 220v ovens with an odd number of segments could get interesting to accurately calculate Wink
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harley guy
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PostPosted: Sat Aug 19, 2006 6:57 am    Post subject: Reply with quote

wow amazing chart.thanks
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Mattax
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PostPosted: Sun Oct 01, 2006 8:09 pm    Post subject: Reply with quote

220 volt wiring. How do I go about physically wiring the 220 volt application for 2 segments? Anyone show me a schematic?
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drcrash
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PostPosted: Mon Oct 02, 2006 10:46 am    Post subject: Reply with quote

Quote:
220 volt wiring. How do I go about physically wiring the 220 volt application for 2 segments? Anyone show me a schematic?


Do you mean two segments, or two zones?

I haven't done either, but I've thought about wiring zones.

I'd say that the easy way to figure it is to figure out what fraction of the heat you want coming out of each zone, pick a number of segments that gives you that fraction, lay them out any way you want, and stretch the coils for different zones different amounts, to fit the layout you want.

So for example, if you wanted the each of the outer 2 rows of coil to be their own zones, and each have a quarter the power of the whole thing, you'd pick four zones, use the calculator to tell how much nichrome coil to cut, and then stretch those pieces of nichrome slightly different amounts to be the outermost row and the next (slightly smaller) row.

(I'd probably cut the segments of coil a little long, stretch them some, and use an ohmmeter to tell me where to do the final cut.)

Paul
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Mattax
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PostPosted: Mon Oct 02, 2006 11:41 am    Post subject: Reply with quote

Thanks for that info, but I was refering to the actual wiring of the 220 volts. I did find some info on this.

For two segments:
One leg of the 220 volt - let's call it 110v since that what it is- gets wired to point A of first segment, other end of first segment is point B which gets wired to second segment, then other end of second segment gets wired to point C. Point C is wired to other leg of 220v - or the other 110v line. Also, one can insert a REOSTAT here to control the amount of heat going to the heating elements so long as the REOSTAT is rated for the AMPS the heating elements will draw.

For three segments and more simply add it in at point B. At this point you now will have a point D at the end.

Two Segment oven:
110v - A - 1st segment - B - 2nd segment - C - REOSTAT - 110v

Three Segment oven:
110v - A - 1st segment - B - 2nd segment - C - 3rd segment - D - REOSTAT - 110v

Four Segment oven:
110v - A - 1st segment - B - 2nd segment - C - 3rd segment - D - 4th segment - E - REOSTAT - 110v

If the above is wrong, please correct me.
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thebluecanary
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PostPosted: Fri Oct 06, 2006 1:25 pm    Post subject: Reply with quote

Mattax wrote:
220 volt wiring. How do I go about physically wiring the 220 volt application for 2 segments? Anyone show me a schematic?


I posted a picture of this at one point. I have to break mine apart because I don't have a breaker the right sizes. If I can remember where I put the image I'll try and post it again.
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drcrash
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PostPosted: Mon Dec 25, 2006 9:42 am    Post subject: Re: 110v/220v Oven calculator Reply with quote

jegner wrote:
For all your 110 to 240v oven wattage and amps calculations:

http://www.imperial-armor.com/ovencalculations.html

Jim


The imperial-armor.com site seems to be down. Any idea when it will be back up? (I want to build an oven this week and I need to run some numbers of the oven calculator.)

Thanks,

Paul
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jegner
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PostPosted: Mon Dec 25, 2006 5:30 pm    Post subject: Reply with quote

I'm having issues with my ISP, but as soon as I can I'll get that site back online.

Jim
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drcrash
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PostPosted: Tue Dec 26, 2006 12:54 pm    Post subject: Reply with quote

I think I can run the numbers by hand if somebody can confirm a couple of things...

(1) the resistance of an inch of unstretched coil (once stretched) is 3 ohms, right?

(2) a 120V 600-watt segment pulls 5 amps, and that requires 8 inches of unstretched coil, because

8 x 3 ohms = 24 ohms resistance, and
120 volts / 24 ohms = 5 amps (volts / ohms = amps), and
120 volts x 5 amps = 600 watts (volts * amps = watts)

Right... ?

If these numbers and calculations are right, this table should be right, unless I screwed up the arithmetic:

Code:

Ohms      Amps     Watts     inches of
        @ 120V    @ 120V   unstretched coil
----   -------    ------   ----------------
 10      12.00     1440         3.34             
 11      10.91     1309         3.66
 12      10.00     1200         4.00
 13       9.23     1107         4.34
 14       8.57     1029         4.67
 15       8.00      960         5.00
 16       7.50      900         5.34
 17       7.06      847         5.67
 18       6.67      800         6.00
 19       6.32      758         6.34
 20       6.00      720         6.67
 21       5.71      686         7.00
 22       5.45      655         7.34
 23       5.22      626         7.67
 24       5.00      600         8.00
 25       4.80      576         8.34
 26       4.62      554         8.67
 27       4.44      533         9.00
 28       4.29      514         9.33
 29       4.14      497         9.67
 30       4.00      480        10.00


Paul
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jegner
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PostPosted: Wed Dec 27, 2006 7:08 am    Post subject: Reply with quote

Looks like the site is back up.

Jim
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drcrash
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PostPosted: Wed Dec 27, 2006 10:23 am    Post subject: Reply with quote

jegner wrote:
Looks like the site is back up.

Jim


Yes---thanks!

But now I'm confused, and need to belatedly ask a couple of questions:

1. What's up with the numbers being calculated for 110V, and coming out more than 20 amps anyway? For 120V, they'd be over 23 amps, and I'd think you'd flip circuit breakers.

Is there headroom hidden in a 20-amp circuit, such that it can generally handle 21 (or 22 or 23) amps without complaint?

Or is there something else going on? My understanding is that when nichrome heats up, its resistance goes up. (By something like 10 percent over something like 1000 degrees.) Is it assumed that the hot resistance will be higher, the amps will be lower, and it won't flip a circuit breaker before the coils heat up enough to bring the amps down?

(My impression is that wall outlet power can be anywhere from 110 to 120 volts, depending on how your power company does things and how long the cables are to your house... is that wrong? If it's right, it seems like calculating things at 110V would be setting things up to flip circuit breakers at 120V...)

I'm trying to build a 5-segment oven, and I want to fit three fixed-wattage segments on one 15-amp circuit and two variable-wattage segments on another. That means my three fixed-wattage segments can only average 5 amps each.

(That's 24 ohms and 600 watts if the voltage is 120V, but 22 ohms and 550 watts at 110V. And if I use the 22-ohm element designed for 110V with wall power that turns out to be 120V, it's 5.45 amps and 654 watts... will that cause problems if I put 3 of them on a 15 amp circuit?)

I could get by with the higher ohms / lower watts segments as far as total heat---I think---but I'm afraid that the elements might operate at such a low temperature that they don't emit enough of the right frequencies to heat plastic well. (Then if I compensate by stretching less coil over the same length segment, so that they burn hotter, I'll go right over my amp budget. Yikes. I don't want to paint myself into a corner here.)

Confusedly,

Paul
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jegner
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PostPosted: Thu Dec 28, 2006 7:36 am    Post subject: Reply with quote

Hello!

I think the calculator takes a few assumptions into account. First, it's based off the idea, that a 20 amp breaker can take slightly more than a flat 20 amps. I can't find any hard numbers, but 2400W 115V oven takes 20.9 amps and is within a +10% range of 20 amps. An electrician can tell you more. But it is my understanding that +10% is normal. Thurston James assumes this in his book as well. For me, I found that my gas generator has a 30 amp 115 V circuit, and I wired it with 10 gague wire. If you 20 amp circuit is long, and wired with 12ga. wire, then you might run into an issue. Also, as the voltage goes down the amps goes up. 110V give the same 2400W, makes the amps go to 21.8. This might be enough to blow the breaker.

Get a multi-meter, and test the circuit you plan to use. See if you have 110 or 115 or even 120v. If you know you have a 20 amp circuit, and can test the actual voltage, you should be able to tweek the wattage on the oven for max output, without blowing the breaker.

Jim
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