On Oct 25, 7:51*am, (Doug Miller) wrote:
In article , Smitty Two wrote:





In article ,
(Doug Miller) wrote:

In article
, Smitty
Two wrote:
In article ,
(Doug Miller) wrote:

Umm, no, actually, that's *my* point: it's counted twice. *Two* amps at
120V.

Doug, you know what you know, and you don't know what you don't know.
Evidently there's a few gaping holes in your understanding of ohm's law.
I'd have to speculate that you've never had an electronics course in
your life, because you're making some erroneous statements about some
pretty basic principles of circuit analysis.

I understand Ohm's law much better than the folks who apparently believe that
200A at 240V is the same thing as 200A at 120V.

I haven't seen anyone here claiming to believe that.

Perhaps you should read more carefully, then. Several posters in this thread
have insisted that the maximum capacity is 200A, period -- while ignoring the
voltage. It's 200A on *each*leg* of the service. That's 200A @ 240V, or 400A
@ 120V.


The maximum capacity of the service is 200Amps period. As Smitty
pointed out, the current is determined by the amount of electrons
passing through a wire each second and is independent of voltage.

You are of the belief that the second hot leg carries an additional
CURRENT, which it does not. In the case of a balanced load, it only
carries the exact SAME current which is flowing in the other hot. As
I said before, the current comes in on one hot while simultaneously
exiting on the other hot. Let's say it's 150 amps. That 150 amps is
coming in on one hot and going out on the other. It reverses each
cycle. That is just like current flowing through a resistor. You
wouldn't count the current in a resistor twice would you?

Now let's add an additional 50amp unbalanced 120Volt load. Now 200
amps comes in on one hot, 150 goes back out as before on the other
hot, and 50 amps goes back via the neutral. Add that up and you
have 200 amps coming into the house and 200 amps leaving the house.
For it to work any other way, current would be piling up or
disappearing somewhere, which is a violation of Kirchoff's law.







A wire capable of carrying 200 amps is capable of carrying 200 amps,
period. It doesn't matter whether it's 1 volt or 1,000,000 volts. An
ampere is defined as a given number of electrons per second.

And *two* wires capable of carrying 200 amps *each* are capable of carrying
*400* amps. What's so hard to understand?

Again, this is like saying a resistor that has 1 amp flowing in it is
carrying 2 amps because 1 amp is coming in and 1 amp is leaving.
Would you say that 14 gauge wire running to an outlet is capable of
carrying 30 amps? These two examples are the same as what is
happening with the service coming into the house.







And, in a series circuit, the current is the same throughout the
circuit. You seem to be claiming otherwise.

No, I've never claimed that. Rather, I've said several times that the two legs
of a residential electrical service are, in effect, two parallel circuits..

They are not simply parallel circuits which would require they have
seperate return paths.


Yes, it can also be considered as a single series circuit -- IF the loads are
exactly balanced. Any unbalanced loads are parallel.

Let's try going at this from the opposite direction. Consider a single-pole
20A circuit breaker supplying a branch circuit. I believe we'd both agree that
circuit can supply a maximum of 20A at 120V.

Now consider a double-pole 20A breaker supplying a 240V circuit. I believe
we'd both agree that circuit can supply a maximum of 20A at 240V.

Re-wire that double-pole 20A breaker with two separate 12-2 cables, so that
it's supplying two 120V circuits. How many amps can that supply at 120V? 20,
or 40?

It's still physically supplying 20 amps because as Smitty pointed out,
that is determined by the number of electrons passing each second.
That hasn't changed. More current doesn't come out of thin air.
But what you have now is that same 20 amps passing through two
circuits. Let's hook up a 6 ohm resistor to each of the new
circuits. You now have 120V across each load, so as far as each load
is concerned, they have 120Volts and 20 amps each. Count that twice
and you have 40 amps of load at 120V driven by the same 20 amps
flowing in the circuit. Look at it at the breaker which is analogous
to the sevice point discussion and you still have 20A flowing, not 40.




Now re-wire it with 3-wire cable, making it instead a multiwire ("Edison")
circuit supplying 120V loads instead of 240V. How many amps can that supply at
120V? 20, or 40?- Hide quoted text -

- Show quoted text -

Here's another example. Take a cardboard box that will be our
"house". Take an extension cord, put a 120Watt bulb on the end of
it, plug it in to a 120V outlet and put the bulb in the box. You
now have a 120volt, 1amp service to the box. 1 amp is flowing in the
circuit.

Now replace the bulb with two 60Watt bulbs in series. Across each
bulb you will have 60 volts and 1 amp will be flowing in each of
them. So, you are supporting two 1 amp loads at 60volts, But what
is flowing in that extension cord? It's still 1 amp, not 2. The
exact same scenario plays out in the 200 amp service coming into the
house, which is why only 200 amps of actual current is ever flowing.