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I was just observing an existing set of connections in my kitchen and was hoping for some clarification. I have a 120/240 stove with a black/red/white/ground. I believe black and red are 120 power and white is the return and then ground, correct? Now with the cooktop (240) the connection is black/red/ground but no white. How is power returned? Via the ground wire?
 

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Reading from black to white or red to white you get 120 VAC if you read from black to red you get 240 VAC. There is actually no such thing as a "return" black white and red are all current carrying conductors ground is not.
 

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I was just observing an existing set of connections in my kitchen and was hoping for some clarification. I have a 120/240 stove with a black/red/white/ground. I believe black and red are 120 power and white is the return and then ground, correct? Now with the cooktop (240) the connection is black/red/ground but no white. How is power returned? Via the ground wire?
The stove is 120/240 volts. 4 wire. H-H-N-G
The cooktop is 240 volts. 3 wire. H-H-G
 

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OK, why doesn't the cooktop (240) require a neutral, i guess, is what I am asking.
You are thinking of the circuits with a common misconception: that current arrives on the hot and returns via the neutral. This is a simplified way of thinking about it, and is useful for troubleshooting, but it simply isn't true.

For an AC circuit, current travels in on one wire and returns on the other for half the cycle, then reverses for the other half. In other words, one wire acts as the return for the other wire depending of which part of the AC cycle you look at. This true for 240 V as well as 120 V circuits. There is no electrical difference between a hot and neutral. The laws of physics don't distinguish between the two. The neutral is tied to ground, however, so we don't notice it's "hotness", but the neutral is as hot as the hot wire. Current both comes and goes on the neutral just like the hot.

So, in this light, the only difference between a 120 and 240 circuit is the voltage. Does that clear it up any?
 

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OK, why doesn't the cooktop (240) require a neutral, i guess, is what I am asking.
Cooktops as a general rule do not an have oven light, clock, timer, or blower fan. All these items usually require 120 Volts, hence the reason why free-standing ranges need dual-rated circuits.

Cooktops have heating elements only, which are rated at 240 Volts. So no neutral connection is required or needed. :whistling2:
 

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Here's my take on it, just to confuse the issue a bit more!

For one half second, electrons will flow to the load on the red wire and back to the street transformer on the black. In the next 1/2 second the electron flow will reverse.
They will now flow from the transformer to the load on the black, through the load and back to the transformer on the red!
In the good old days, heating elements required the use of a neutral as the amount of heat output was changed by applying different voltages to the element. In those days current would sometimes flow in the neutral.
Now, however the current is controlled electronically and isn't dependant on switching voltages.
 

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In the good old days, heating elements required the use of a neutral as the amount of heat output was changed by applying different voltages to the element. In those days current would sometimes flow in the neutral.
Now, however the current is controlled electronically and isn't dependant on switching voltages.
HUH?????
Either an element is 120v or it is 240v. The ONLY time current would flow on a neutral is with a 120v element. Maybe that's what you meant?
 

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HUH?????
Either an element is 120v or it is 240v. The ONLY time current would flow on a neutral is with a 120v element. Maybe that's what you meant?
They were center tapped 240 volts Pete. 120 volts would be applied to both poles. 240 would be applied to both poles or 120 volts from one pole to the center tap and so on! I forget how many heat levels could be attained, but it may have been as much as eight!
 

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HUH?????
Either an element is 120v or it is 240v. The ONLY time current would flow on a neutral is with a 120v element....

Not at all. Consider the following: Take two elements, both rated at 240 Volts, say 1000 watts each. They are both swirled together, making up a flat platform.

Using a 5 position selector switch, you can obtain the following heat settings --->

HIGH: 240 applied to both sections 2000 watts
MED/HIGH: 240 applied to one section 1000 watts
MED: 240 applied to both elements, in series 500 watts
LOW: 120 applied to one section 250 watts
WARM: 120 applied to both sections, in series 125 watts

This is typical of the older electric ranges before the percentage/interval (infinite) controls were introduced.

Also, consider that Frigidaire once had an element called "Speed heat". Essentially it was a 120 Volt element that was connected to a special control. When you first switched it on, it applied 240 Volts to that element, causing it to heat up rapidly. After a short period of time, the control would switch back to 120 Volt operation, keeping the element from burning out.

They eventually discontinued using that scenario due to the high number of element or control burnouts (imagine that?)
 

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OK, I see.
I wasn't implying that a 240v element wouldn't work at 120v, I've just never seen a system like that before.
:thumbsup:
 

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Not at all. Consider the following: Take two elements, both rated at 240 Volts, say 1000 watts each. They are both swirled together, making up a flat platform.

Using a 5 position selector switch, you can obtain the following heat settings --->

HIGH: 240 applied to both sections 2000 watts
MED/HIGH: 240 applied to one section 1000 watts
MED: 240 applied to both elements, in series 500 watts
LOW: 120 applied to one section 250 watts
WARM: 120 applied to both sections, in series 125 watts

This is typical of the older electric ranges before the percentage/interval (infinite) controls were introduced.

Also, consider that Frigidaire once had an element called "Speed heat". Essentially it was a 120 Volt element that was connected to a special control. When you first switched it on, it applied 240 Volts to that element, causing it to heat up rapidly. After a short period of time, the control would switch back to 120 Volt operation, keeping the element from burning out.

They eventually discontinued using that scenario due to the high number of element or control burnouts (imagine that?)
Sparky, you just explained that better than I ever could! My hats off to you! :thumbup:
 
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