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.

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?

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.
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?

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?

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.

[snip]

Oh, you mean that if both legs are fully loaded, there's no current being
drawn at all?

Sorry, but you don't understand. The current in the neutral is in fact zero,
if both legs are loaded exactly equally -- and if all the loads supplied are
120V loads, then it is in fact drawing 400A @ 120V.

That current is 200A. That 400A is obviously not in the neutral. WHERE
is it?

On Sat, 24 Oct 2009 18:17:14 GMT, (Doug Miller)
wrote:

In article , wrote:

Consider this simple circuit analogy which is exactly what you would
have with a balanced load on a 240V service. It's a 240V voltage
source powering two 120ohm resistors.

____________ 240V___________
I I
I I
I I
---------120ohm---------120ohm---------
a b c


There is only 1 amp of actual current flowing in the circuit. Across
each resistor there is 120Volts and 1 amp of current flowing. So,
yes you have 1 amp flowing in EACH load, it is supporting two 1 amp
loads, but it's the same physical current flowing through each load.
The "service" is only supplying 1 amp of actual current, not 2.


What voltage do you measure between a and b? Between c and b?
What current do you measure between a and b? Between c and b?

That's what I meant when I said a 200 amp service cannot supply 400
amps of current.

But it can. 200A at 120V on each leg is a total of 400A at 120V. The two legs
of a residential electrical service are, in effect, two parallel circuits.
200A flowing in each of two parallel circuits is 400A total, not 200A.


You have a SERIES circuit (considering that the neutral is effectively
disconnected).

[snip]

On Sat, 24 Oct 2009 23:55:15 GMT, (Doug Miller)
wrote:

In article , wrote:
On Oct 24, 2:17=A0pm, (Doug Miller) wrote:
In article =
..com, wrote:

[...]
What voltage do you measure between a and b? Between c and b?

120 Volts
120 Volts

What current do you measure between a and b? Between c and b?

1 amp and it's THE SAME 1 AMP current. It just gets counted twice.
Which once again is my point.

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


That makes no sense. 1A counted twice is 1A. No amount of counting
changes what exists.

I'm alone in my room. Therefore, counting the number of people in the
room shows 1. Now, I look in a mirror and count again. Now there's TWO
people in the room.

You have ONE 50-foot rope. Every time you see rope count it. Now you
have 10 ropes.

There is only 1 amp flowing in the
actual complete circuit, just like there is only a maximum of 200
physical amps flowing in a 200 amp service.

OK, so there's 120V @ 1A flowing between a and b = 120W. And there's 120V @ 1A
flowing between b and c = 120W. Total = 240W.

240W / 120V = 2A

In a house, here's how the same thing happens. I hook a 120Volt
light bulb that draws 1 amp on one hot leg and a 120volt fan that
draws one amp on the other hot leg. The 1 amp current comes in one
leg, goes through the bulb, through the fan and out the other hot
leg. That's still an actual current of only 1 amp, though it runs
through two 1 amp loads.

Wrong. Two 1 amp loads = *two* amps, not one.


You still haven't shown where that TWO amp current is.

Is it in the first load? There's just 1A there.
Is it in the second load? There's just 1A there.
Is it in the first supply wire? There's just 1A there.
Is it in the second supply wire? There's just 1A there.
Is it in the neutral wire? There's ZERO current there.
Is it in the air? There's heat there, but no current.

WHERE is it?

[snip]

In article , wrote:
On Oct 25, 7:51=A0am, (Doug Miller) wrote:
In article -media=
..com, Smitty Two wrote:





In article ,
(Doug Miller) wrote:

In article
, S=
mitty
Two wrote:
In article ,
(Doug Miller) wrote:

Umm, no, actually, that's *my* point: it's counted twice. *Two* amp=
s 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 l=
aw.
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 belie=
ve 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 thr=
ead
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.

You are wrong. It does -- in the case of 120V loads.

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.

IF it's supplying a 240V load, yes. If it's supplying a 120V load, then it
exits on the neutral.

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?

So is it your position that a 200A 240V service is incapable of supplying more
than 200A at 120V = 24kVA?

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.

At 240V.

For it to work any other way, current would be piling up or
disappearing somewhere, which is a violation of Kirchoff's law.

How much power can be supplied by a 200A, 240V service? 24kVa, or 48kVA?

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.

No, it's not. It's like saying that *two* resistors IN PARALLEL with 1 amp
flowing through each have a total current of two amps. Do you disagree?

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.

No, they are not. Keep thinking about it until you realize why those two
examples are not the same, and then you'll understand where you've made your
mistake.



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.

Wrong again.

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

ON EACH CIRCUIT

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.

You've just made current *disappear* into thin air: supplying a single 240V
circuit, it's supplying 4800W of power -- but now you claim it's supplying
only 2400W when connected to two 120V circuits. Where did that other 2400W go
to?

But what you have now is that same 20 amps passing through two
circuits.

20 amps through each of two circuits = 40 amps.

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

THANK YOU. Discussion over. That's what I've been trying to tell you for three
days now.

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.

20A in each of two parallel legs = 40 amps total. Note that these do have
separate returns...


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?

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.

Measured at 120V, yes. But this isn't the same situation, quite, as a
residential service. Keep the two ends of that circuit at a potential
difference of 120V, and *ground* the point in between the two light bulbs.
Then you have 60V flowing through each 60W light bulb = 1 amp *each* = 2 amps
*total* in the parallel circuits.

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.

So you still contend that a 200A 240V service cannot supply more than 24kVA at
120V?

In article , Sam E wrote:
[snip]

Oh, you mean that if both legs are fully loaded, there's no current being
drawn at all?

Sorry, but you don't understand. The current in the neutral is in fact zero,
if both legs are loaded exactly equally -- and if all the loads supplied are
120V loads, then it is in fact drawing 400A @ 120V.

That current is 200A. That 400A is obviously not in the neutral. WHERE
is it?

There's no current in the neutral if the loads are balanced.

In article , Sam E wrote:
On Sat, 24 Oct 2009 18:17:14 GMT, (Doug Miller)
wrote:

In article
,
wrote:

Consider this simple circuit analogy which is exactly what you would
have with a balanced load on a 240V service. It's a 240V voltage
source powering two 120ohm resistors.

____________ 240V___________
I I
I I
I I
---------120ohm---------120ohm---------
a b c


There is only 1 amp of actual current flowing in the circuit. Across
each resistor there is 120Volts and 1 amp of current flowing. So,
yes you have 1 amp flowing in EACH load, it is supporting two 1 amp
loads, but it's the same physical current flowing through each load.
The "service" is only supplying 1 amp of actual current, not 2.


What voltage do you measure between a and b? Between c and b?
What current do you measure between a and b? Between c and b?

That's what I meant when I said a 200 amp service cannot supply 400
amps of current.

But it can. 200A at 120V on each leg is a total of 400A at 120V. The two legs
of a residential electrical service are, in effect, two parallel circuits.
200A flowing in each of two parallel circuits is 400A total, not 200A.


You have a SERIES circuit (considering that the neutral is effectively
disconnected).

[snip]

Wrong. The neutral is "effectively disconnected" *only* if the loads on the
two legs are exactly the same. The two legs function as two parallel circuits
with respect to 120V loads. Obviously they are indeed in series WRT 240V
loads.

In article , Gary H wrote:
On Sat, 24 Oct 2009 23:55:15 GMT, (Doug Miller)
wrote:

In article
,
wrote:
On Oct 24, 2:17=A0pm, (Doug Miller) wrote:
In article =
..com, wrote:

[...]
What voltage do you measure between a and b? Between c and b?

120 Volts
120 Volts

What current do you measure between a and b? Between c and b?

1 amp and it's THE SAME 1 AMP current. It just gets counted twice.
Which once again is my point.

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


That makes no sense. 1A counted twice is 1A. No amount of counting
changes what exists.

1A in _each of two parallel circuits_ is a total of 2A.
[...]

You still haven't shown where that TWO amp current is.

Is it in the first load? There's just 1A there.
Is it in the second load? There's just 1A there.

The two loads are in parallel, not in series. 1 + 1 = 2.

Is it in the first supply wire? There's just 1A there.
Is it in the second supply wire? There's just 1A there.

Two parallel circuits, 1A in each. 1 + 1 = 2.

Is it in the neutral wire? There's ZERO current there.
Is it in the air? There's heat there, but no current.

WHERE is it?

1 amp in each of the two hot legs -- which with respect to 120V loads, are
effectively two separate parallel circuits.

On Sun, 25 Oct 2009 18:46:17 GMT, (Doug Miller)
wrote:

In article , Sam E wrote:
[snip]

Oh, you mean that if both legs are fully loaded, there's no current being
drawn at all?

Sorry, but you don't understand. The current in the neutral is in fact zero,
if both legs are loaded exactly equally -- and if all the loads supplied are
120V loads, then it is in fact drawing 400A @ 120V.

That current is 200A. That 400A is obviously not in the neutral. WHERE
is it?

There's no current in the neutral if the loads are balanced.

No current. I was replying to the person who claimed 400A.

[snip]


WHERE is it?

1 amp in each of the two hot legs --

Of course. The problem is WHERE is the 2A.

which with respect to 120V loads, are
effectively two separate parallel circuits.

No. That would require identical sources. These sources are not
identical, but opposite. The difference can be up to 339V (the peak
value for 240V RMS).

In the circuit you describe there is ZERO current in the neutral. This
is the same as the neutral not being there (current in that wire is 0A
in either case). What you have is a SERIES circuit. It is the same
current going through both resistors, therefore addition is not
appropriate here.

This reminds me of a story I heard a few years ago. Three 12-year-old
boys wished they could vote. Since the voting age was 18, the boys
decided that if they went together they'd get 2 votes.

12 + 12 + 12 = 18 * 2

The fact that you can do arithmetic doesn't mean it's appropriate to
do so.
--
61 days until the winter solstice celebration

Mark Lloyd
http://notstupid.us

"How could you ask me to believe in God when there's
absolutely no evidence that I can see?" -- Jodie Foster

[snip]


You have a SERIES circuit (considering that the neutral is effectively
disconnected).

[snip]

Wrong. The neutral is "effectively disconnected" *only* if the loads on the
two legs are exactly the same.

Which they are (either in the 200A+200A example or the 1A+1A one).

The two legs function as two parallel circuits
with respect to 120V loads.

In a parallel circuit BOTH ends of the loads are connected together
(or at least to identical voltages). Neither is true here.

Obviously they are indeed in series WRT 240V
loads.

Strangely, I get the idea that you actually know this stuff.

In this 200A service there are THREE current-carrying conductors.
Each of these conductors is of the proper size to carry 200A. OK so
far?

You say (when this service is fully loaded) that two of these
conductors is carrying 200A (for a total of 400A, as you say).

Then where is that 400A going? The only remaining conductor is the
neutral, a big enough conductor for 200A (yes, this 400A was at 120V
but current is still current and voltage doesn't change the
conductor's current capacity).





Somehow I'm imagining a bridge that can handle 200 cars per minute,
but that can be 400 if half the cars are blue :-)

In article , Sam E wrote:
[snip]


You have a SERIES circuit (considering that the neutral is effectively
disconnected).

[snip]

Wrong. The neutral is "effectively disconnected" *only* if the loads on the
two legs are exactly the same.

Which they are (either in the 200A+200A example or the 1A+1A one).

And that almost never happens in real life, either....

The two legs function as two parallel circuits
with respect to 120V loads.

In a parallel circuit BOTH ends of the loads are connected together
(or at least to identical voltages). Neither is true here.

Wrong -- both are true.

Obviously they are indeed in series WRT 240V
loads.

Strangely, I get the idea that you actually know this stuff.

In this 200A service there are THREE current-carrying conductors.
Each of these conductors is of the proper size to carry 200A. OK so
far?

OK

You say (when this service is fully loaded) that two of these
conductors is carrying 200A (for a total of 400A, as you say).

400A @ 120V, or 200A @ 240V, yes.

Then where is that 400A going? The only remaining conductor is the
neutral, a big enough conductor for 200A (yes, this 400A was at 120V
but current is still current and voltage doesn't change the
conductor's current capacity).

Somehow I'm imagining a bridge that can handle 200 cars per minute,
but that can be 400 if half the cars are blue :-)

Cute. Just answer these questions; assume a 240V 200A service.

What is the maximum power that service can provide?

If all the loads supplied by that service are 120V loads (e.g. blender,
toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do you get
when you divide that maximum power by 120V?

On Oct 24, 10:11*am, Gary H wrote:
On Fri, 23 Oct 2009 19:54:26 GMT, (Doug Miller)
wrote:



In article , wrote:
On Oct 22, 4:10=A0pm, (Doug Miller) wrote:
In article =
..com, wrote:

Aside from the 80% rule,

Which doesn't apply...

you can't get 400 amps out of a 200amp service.

Of course you can; it just depends on which circuits are in use. If you're
using only 120V circuits, you can get 200A on *each* leg. 200A @ 240V is the
same power as 400A @120V.

Yes but physically, a current of 200 amps is all that is actually
flowing. * Put a meter on it and you will measure 200 amps, not 400.
It's a simple matter of Kirchoffs law.

200 amps on _each leg_. It's a total of (up to) 400 amps at 120V.

200A on each leg. Where's the 400A?

Being able to add to numbers* doesn't mean reality works that way.

[snip]

* - Actually, that's incorrect too. The addends are out of phase, so
200 + 200 = 0.

Assume you are using one leg at 200 amps, that is all the breaker
will handle that is 120 volts X 200 amps or 24,000 watts. If you
again max out the breaker with 200 amps flowing on both sides that is
240 volts x 200 amps or 48000 watts. Thats the same as 120 X 400 amps.
I think the OP wanted to know if he could get a total of 400 amps at
120VAC. Lets rephrase that to could he power 400 individual 1 amp 120
VAC loads from this box under residential conditions. The answer is
yes but that sounds a lot like a commercial installation to me where
the answer would be NO. I think this is a case of getting the right
answers to the wrong question.


Jimmie

On Oct 25, 9:15*pm, Sam E wrote:
On Sun, 25 Oct 2009 18:46:17 GMT, (Doug Miller)
wrote:

In article , Sam E wrote:
[snip]

Oh, you mean that if both legs are fully loaded, there's no current being
drawn at all?

Sorry, but you don't understand. The current in the neutral is in fact zero,
if both legs are loaded exactly equally -- and if all the loads supplied are
120V loads, then it is in fact drawing 400A @ 120V.

That current is 200A. That 400A is obviously not in the neutral. WHERE
is it?

There's no current in the neutral if the loads are balanced.

No current. I was replying to the person who claimed 400A.

Assume you are using one leg at 200 amps, that is all the breaker
will handle that is 120 volts X 200 amps or 24,000 watts. If you
again max out the breaker with 200 amps flowing on both sides that is
240 volts x 200 amps or 48000 watts. Thats the same as 120 X 400 amps.
I think the OP wanted to know if he could get a total of 400 amps at
120VAC. Lets rephrase that to could he power 400 1 amp 120 VAC loads
from this box under residential conditions. The answer is yes but that
sounds a lot like a commercial installation to me where the answer
would be NO. I think this is a case of getting the right answers to
the wrong question.

On Oct 25, 2:45*pm, (Doug Miller) wrote:
In article , wrote:





On Oct 25, 7:51=A0am, (Doug Miller) wrote:
In article -media=
..com, Smitty Two wrote:

In article ,
(Doug Miller) wrote:

In article
, S=
mitty
Two wrote:
In article ,
(Doug Miller) wrote:

Umm, no, actually, that's *my* point: it's counted twice. *Two* amp=
s 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 l=
aw.
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 belie=
ve 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 thr=
ead
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. *

You are wrong. It does -- in the case of 120V loads.

Here we go again.....



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.

IF it's supplying a 240V load, yes. If it's supplying a 120V load, then it
exits on the neutral.

False. I clearly stated here that it's a balanced load. With a
balanced 120V load, the exact same current comes in on one hot and
exists on the other. In the case of a 200 amp service, that current
is a max of 200 amps.




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?

So is it your position that a 200A 240V service is incapable of supplying more
than 200A at 120V = 24kVA?

No and I and everyone else have tried to explain that to you. Go
back many posts to the simple circuit diagram I drew:

..


____________ 240V___________
I I
I I
I I
---------120ohm---------120ohm---------
a b c


You have a 240 volt voltage source as our "service" connected to two
120 ohm resistors in SERIES.

How much current is flowing in that circuit?
1 amp

How much current is flowing in the first resistor?
1 amp

How much current is flowing in the second resistor?
1 amp

What is the voltage across each resistor?
120V

What is the power in each resistor?
120W

So, you have 1 amp flowing in SERIES through each load, so you do have
two loads of 1 amp at 120V, but only 1 amp of current is actually
flowing in the circuit which comprises the "service"

Capishe?






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.

At 240V.

Now we're back to what Smitty tried to explain to you. Current has
nothing to do with voltage. It's based on the amount of charge, ie
electrons, passing a point per second. 200 amps is still exactly
200 amps whether it's at a potential of 240V, 120V or a million volts.

And btw, the voltage is not entirely 240V in the above example I gave
either. 150amps is flowing at 240V and 50 is flowing at 120V. If it
were simply all at 240V, you'd have 48KW of power here. Actually
it's 150X240+50*120=42KW




For it to work any other way, current would be piling up or
disappearing somewhere, which is a violation of Kirchoff's law.

How much power can be supplied by a 200A, 240V service? 24kVa, or 48kVA?

That's been asked an answered many times in this thread. It's 48,

Now answer my question. What is the maximum current that is actually
flowing in the 3 wire cable of a 200 amp service? If you say it's
more than 200 amps, outline an example and using Kirchoff's law, trace
for us the current flowing in all 3 conductors.







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.

No, it's not. It's like saying that *two* resistors IN PARALLEL with 1 amp
flowing through each have a total current of two amps. Do you disagree?

Absolutely disagree. I gave you an example before. Take a 120W,
120V light bulb and place it between one hot leg and neutral. Take
a 120V fan drawing 1 amp and place it between the other hot leg and
neutral. You now have a balanced load drawing 1 amp. There is 1 amp
flowing in one hot and out the other. The neutral is carrying 0
amps. You are supporting two 1 amp, 120V loads. Total amps flowing
in the service: 1 amp. Those two loads appear in SERIES across the
two hots.




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.

No, they are not. Keep thinking about it until you realize why those two
examples are not the same, and then you'll understand where you've made your
mistake.


Several people in this thread say I'm right. No one is saying you are
right. So, maybe it's time that you did some more thinking.




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.

Wrong again.




Sigh





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

ON EACH CIRCUIT

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.

You've just made current *disappear* into thin air: supplying a single 240V
circuit, it's supplying 4800W of power -- but now you claim it's supplying
only 2400W when connected to two 120V circuits. Where did that other 2400W go
to?


Again, you are somehow trying to mix current, which is measured in
amps with power and voltage.



But what you have now is that same 20 amps passing through two
circuits. *

20 amps through each of two circuits = 40 amps.

Yes, 20 amps through two loads in series. Yes it's supporting two 20
amp loads. But what current is passing through the breaker? 20
amps




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

THANK YOU. Discussion over. That's what I've been trying to tell you for three
days now.

No, for 3 days you've been telling everyone here that in the case of a
service, you get more amps because there is a second hot conductor.
That is flat out wrong. Refer again to the box example later in the
thread, where there is no second hot.



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.

20A in each of two parallel legs = 40 amps total. Note that these do have
separate returns...

Oh no, there you go again. Counting current twice. If that
breaker had 20 amps flowing through it at 240V, then it had a 12 ohm
load on it. So, now to make it into a 120V circuit, we just remove
the 12 ohm load, put two 6 ohm loads in series on it. Now across each
6 ohm resistor you have 120V, with the same 20 amps flowing
sequentially through both and suddenly the breaker is now magically
carrying 40 amps?





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?
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. *

Measured at 120V, yes.

Again, per Smitty and the rest of the world, measuring current has
nothing to do with measuring voltage.



But this isn't the same situation, quite, as a
residential service.

It is EXACTLY analogous to a residential service with a balanced 120V
load. You have a 120V, 1 amp "service" supplying two 60W, 60volt
loads. You have 1 amp flowing in series through the two loads, but
ONLY 1 AMP IS FLOWING IN THE SERVICE. If it is not the same as a
residential service, tell us exactly what the difference is and why
the exact same principles do not apply.




Keep the two ends of that circuit at a potential
difference of 120V, and *ground* the point in between the two light bulbs..
Then you have 60V flowing through each 60W light bulb = 1 amp *each* = 2 amps
*total* in the parallel circuits.

Good grief. If you did provide an alternative "neutral" return path
at the point between the bulbs, it would matter not a wit. Just as
in the actual residential service, the load is balanced and zero
current would flow in the neutral. That is why I left it out as I
wanted to keep it as simple as possible. If you like, I can draw you
the circuit diagram that represents a center tap 240V service, but it
doesn't change how current is counted.



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.

So you still contend that a 200A 240V service cannot supply more than 24kVA at
120V?- Hide quoted text -



Again, please stop misquoting me. Neither I nor anyone else here
ever said any such thing.

Let me restate what I've said all along:

In a 200 amp service entering a house, there is a max of 200 amps of
actual current flowing. You don't count current twice on a service
cable anymore than you would on an extension cord.

Here's a simple series of questions:


1 I have a big 240V water heater that draws 200 amps and is
connected to a 200amp service via the two hot legs.

How much current is flowing in

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house

2 Now instead of the single 240V water heater, I have two 120V water
heaters that draw 200 amps each. One is connected between hot leg 1
and neutral, the other between hot leg 2 and neutral.

How much current is flowing in:

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house


3 Is the situation in #2 above an example of a parallel circuit or a
series circuit?



4 I now disconnect the water heater that was connected to leg 2 in
the previous example. You now have one 120V, 200 amp water heater
connected to leg 1 and neutral.

How much current is flowing in:

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house

On Sun, 25 Oct 2009 18:46:17 GMT, in alt.home.repair,
(Doug Miller) wrote:

In article , Sam E wrote:
[snip]

Oh, you mean that if both legs are fully loaded, there's no current being
drawn at all?

Sorry, but you don't understand. The current in the neutral is in fact zero,
if both legs are loaded exactly equally -- and if all the loads supplied are
120V loads, then it is in fact drawing 400A @ 120V.

That current is 200A. That 400A is obviously not in the neutral. WHERE
is it?

There's no current in the neutral if the loads are balanced.

How can people get this so wrong? It's basic electricity, you all should
have learned this in high school.

In a 200A 240V split phase service, any SINGLE 120v load can draw up to
200A, no more. Because it is split phase, you can have two such loads. Now
the math. 200A@120V + 200A@120V = 200A@240V, NOT 400A@120V. Because two
200A 120V loads on a single split phase panel are in fact operating in
series (whether you deliberately wired them that way or not), presenting a
de facto 200A 240V load on the panel. And, yes, in that case the neutral
conductor current is zero.

--
Due to Usenet spam, emailed replies must pass an intelligence test: if
you want me to read your reply, be sure to include this line of text in
your email, but remove this line before sending, otherwise my filters
will delete your email with all due prejudice. Thanks!

On Oct 25, 11:08*pm, (Doug Miller) wrote:
In article , Sam E wrote:
[snip]

You have a SERIES circuit (considering that the neutral is effectively
disconnected).

[snip]

Wrong. The neutral is "effectively disconnected" *only* if the loads on the
two legs are exactly the same.


But a balanced load is exactly what was shown in the simple circuit
example above that he understood and is discussing.



Which they are (either in the 200A+200A example or the 1A+1A one).

And that almost never happens in real life, either....

Which matters not a wit. Unless of course you are trying to get
close to the maximum capacity of the service. If it's totally
unbalanced, guess what? You get 200 amps at 120V, or exactly half
the power capacity of the service. Gee, I wonder why? Could it be
that it's because the service can only handle 200AMPS? And that with
a 200 amp unbalanced load at 120V, 200 amps is coming in on one hot
and it's all going back on the neutral?








The two legs function as two parallel circuits
with respect to 120V loads.

In a parallel circuit BOTH ends of the loads are connected together
(or at least to identical voltages). Neither is true here.

Wrong -- both are true.

Wow, it's getting really strange here. Of course, by definition, a
parallel circuit is one where the ends of the individual elements are
connected together. A series circuit is one where elements are
connected one after the other, in series.








Obviously they are indeed in series WRT 240V
loads.

Strangely, I get the idea that you actually know this stuff.

In this 200A *service there are THREE current-carrying conductors.
Each of these conductors is of the proper size to carry 200A. OK so
far?

OK



You say (when this service is fully loaded) that two of these
conductors is carrying 200A (for a total of 400A, as you say).

400A @ 120V, or 200A @ 240V, yes.

And there you go again, inserting voltage into a question of
amperage. Amperage is a measure of the charge, ie electrons passing
through the conductor and IS NOT LINKED TO VOLTAGE.








Then where is that 400A going? The only remaining conductor is the
neutral, a big enough conductor for 200A (yes, this 400A was at 120V
but current is still current and voltage doesn't change the
conductor's current capacity).

Somehow I'm imagining a bridge that can handle 200 cars per minute,
but that can be 400 if half the cars are blue :-)

Cute. Just answer these questions; assume a 240V 200A service.

What is the maximum power that service can provide?


You;ve asked that question multiple times and it's always been
answered the same: 48KVA

Now answer his question that you avoided. Apply Kirchoff's law and
tell us where current is flowing in a 200 amp service cable that
totals up to 400 amps. All of us here agree and can account for
200amps. So explaing the missing 200.




If all the loads supplied by that service are 120V loads (e.g. blender,
toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do you get
when you divide that maximum power by 120V?

If it's a balanced load, you get 400 amps because half the load is in
SERIES with the other half. As I've outlined about 6 times now, you
have 200 amps coming in on one hot, going through the loads in series
and then out the other hot. 200 amps is flowing in the service. If
you say it's 400, then why isn't it 2 amps that flows in a 120watt
light bulb plugged into an outlet? 1 amp comes in one wire, 1 amp
goes out the other wire. Yet the world agrees that only 1 amp is
flowing, not 2.

If it's a totally unbalanced 120V load, then you can't just divide the
power by 120 as youu imply, because you have 200 amps flowing in on
one hot, and 200 amps flowing out on the neutral. So you have a
120V, 200 amp load and only a power of 24KVA.

No matter how you slice and dice it, there is a max of 200 amps
flowing in the service. Since you believe otherwise, outline the
current flows as I have here and how it adds up to greater than 200
amps flowing in the service conductors.

wrote:
On Oct 25, 2:45 pm, (Doug Miller) wrote:

....
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?

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.

This is the only error I picked up. The supply voltage, as stated, is
120V in both cases. In the second case the 2 60W bulbs would have to be
in parallel to give a load of 120W and 1A.
Assuming the light bulbs are linear resistances, with 60V across a 120V
bulb you would get 1/2 the rated current, or 1/4A which gives an
effective wattage in the 2nd case of 30W.

That isn't what you intended.

....
Let me restate what I've said all along:

The arguments have gotten so twisted let me start here.

In a 200 amp service entering a house, there is a max of 200 amps of
actual current flowing. You don't count current twice on a service
cable anymore than you would on an extension cord.

Here's a simple series of questions:


1 I have a big 240V water heater that draws 200 amps and is
connected to a 200amp service via the two hot legs.

How much current is flowing in

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house

2 Now instead of the single 240V water heater, I have two 120V water
heaters that draw 200 amps each. One is connected between hot leg 1
and neutral, the other between hot leg 2 and neutral.

How much current is flowing in:

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house


3 Is the situation in #2 above an example of a parallel circuit or a
series circuit?



4 I now disconnect the water heater that was connected to leg 2 in
the previous example. You now have one 120V, 200 amp water heater
connected to leg 1 and neutral.

How much current is flowing in:

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house


Everyone, I believe, has the same the answers (though I'm not sure what
"d" is).

The question from the OP, as I understand it, is with a panel feed at
200A 240V can you supply 200A of 120V load or 400A of 120V load.

It is case #2 above. You can supply 400A of 120V load. You can't supply
a 400A 120V load, but with the load split between the legs you can
supply a total of 400A of 120V load, half of it from each leg. In that
case the hot legs run at 200A and the neutral is zero. You don't have
400A on any wire. I assume that is not a problem for you. That is all I
read Doug as saying. I agree.

Its gotta be a point-of-view problem.

--
bud--

On Oct 26, 12:45*pm, bud-- wrote:
wrote:
On Oct 25, 2:45 pm, (Doug Miller) wrote:

* ....
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?

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. *

This is the only error I picked up. The supply voltage, as stated, is
120V in both cases. In the second case the 2 *60W bulbs would have to be
in parallel to give a load of 120W and 1A.
Assuming the light bulbs are linear resistances, with 60V across a 120V
bulb you would get 1/2 the rated current, or 1/4A which gives an
effective wattage in the 2nd case of 30W.

That isn't what you intended.


Yes, I agree. good catch.

120W bulb - 120 ohms
60 W bulb - 240 ohms
240W bulb - 60 ohms


So, in my example I should have used two 240 watt bulbs in series
which would be the same resistance as the 120watt bulb. Actuallly, I
should have used a simple resistor or similar, because the resistance
of light bulbs is not a constant, temp dependent, etc.

But the example, corrected, still holds. You would have 60 volts and
1 amp flowing across each bulb.





*....

Let me restate what I've said all along:

The arguments have gotten so twisted let me start here.





In a 200 amp service entering a house, there is a max of 200 amps of
actual current flowing. *You don't count current twice on a service
cable anymore than you would on an extension cord.

Here's a simple series of questions:

1 * I have a big 240V water heater that draws 200 amps and is
connected to a 200amp service via the two hot legs.

How much current is flowing in

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house

2 *Now instead of the single 240V water heater, I have two 120V water
heaters that draw 200 amps each. * *One is connected between hot leg 1
and neutral, the other between hot leg 2 and neutral.

How much current is flowing in:

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house

3 *Is the situation in #2 above an example of a parallel circuit or a
series circuit?

4 *I now disconnect the water heater that was connected to leg 2 in
the previous example. *You now have one 120V, 200 amp water heater
connected to leg 1 and neutral.

How much current is flowing in:

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house

Everyone, I believe, has the same the answers (though I'm not sure what
"d" is).


I'm not so sure there is agreement as to the answers. And if there
is agreement, then I don't see how there can be disagreement on how
many amps are flowing on the service cable. If you have X amps
coming in and X amps going out in a circuit, then that means X amps,
no?



The question from the OP, as I understand it, is with a panel feed at
200A 240V can you supply 200A of 120V load or 400A of 120V load.

It is case #2 above. You can supply 400A of 120V load. You can't supply
a 400A 120V load, but with the load split between the legs you can
supply a total of 400A of 120V load, half of it from each leg. In that
case the hot legs run at 200A and the neutral is zero. You don't have
400A on any wire. I assume that is not a problem for you. That is all I
read Doug as saying. I agree.

Its gotta be a point-of-view problem.

--

I don;t see it as a point of view problem at all. How many amps are
actually flowing in a 200 amp service to a house? You draw an
imaginary plane and answer the question of how many amps are flowing
in and how many are flowing out. If it is indeed 200 in, 200 out,
then that is 200 amps period. You can have 200 amps flowing between
the two hots. You can have 200 amps flowing between hot 1 and the
neutral. You can have 200 amps flowing between hot 2 hot and the
neutral, Any way you slice and dice it, it's still 200 amps.

If you can really have 400 amps of real current flow in the service,
then maybe Doug can answer this. Suppose I have a 120 volt load that
takes 400 amps. I connect it as a single 120V load to a 200 amp
service. What happens?

A - Eveything works peechy keen, because 120V* 400amps = 48KVA, at the
service limit, so 400 amps flows just fine.

B - The service cable burns up, because the only way you can supply
that 400amps is by the load being balanced, in which case it appears
as a series load and the service is actually pulling 200amps through
one hot and back the other. Which means that it would ONLY work if
you had two 200 amp, 120V loads connected to OPPOSIITE legs, and hence
acting as a SERIES circuit.





bud--- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

On Oct 26, 1:44*pm, wrote:
On Oct 26, 12:45*pm, bud-- wrote:





wrote:
On Oct 25, 2:45 pm, (Doug Miller) wrote:

* ....
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?

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. *

This is the only error I picked up. The supply voltage, as stated, is
120V in both cases. In the second case the 2 *60W bulbs would have to be
in parallel to give a load of 120W and 1A.
Assuming the light bulbs are linear resistances, with 60V across a 120V
bulb you would get 1/2 the rated current, or 1/4A which gives an
effective wattage in the 2nd case of 30W.

That isn't what you intended.

Yes, I agree. *good catch.

120W bulb - *120 ohms
60 W bulb *- 240 ohms
240W bulb - 60 ohms

So, in my example I should have used two 240 watt bulbs in series
which would be the same resistance as the 120watt bulb. * Actuallly, I
should have used a simple resistor or similar, because the resistance
of light bulbs is not a constant, temp dependent, etc.

But the example, corrected, still holds. * You would have 60 volts and
1 amp flowing across each bulb.







*....

Let me restate what I've said all along:

The arguments have gotten so twisted let me start here.

In a 200 amp service entering a house, there is a max of 200 amps of
actual current flowing. *You don't count current twice on a service
cable anymore than you would on an extension cord.

Here's a simple series of questions:

1 * I have a big 240V water heater that draws 200 amps and is
connected to a 200amp service via the two hot legs.

How much current is flowing in

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house

2 *Now instead of the single 240V water heater, I have two 120V water
heaters that draw 200 amps each. * *One is connected between hot leg 1
and neutral, the other between hot leg 2 and neutral.

How much current is flowing in:

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house

3 *Is the situation in #2 above an example of a parallel circuit or a
series circuit?

4 *I now disconnect the water heater that was connected to leg 2 in
the previous example. *You now have one 120V, 200 amp water heater
connected to leg 1 and neutral.

How much current is flowing in:

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house

Everyone, I believe, has the same the answers (though I'm not sure what
"d" is).

I'm not so sure there is agreement as to the answers. * And if there
is agreement, then I don't see how there can be disagreement on how
many amps are flowing on the service cable. * *If you have X amps
coming in and X amps going out in a circuit, then that means X amps,
no?



The question from the OP, as I understand it, is with a panel feed at
200A 240V can you supply 200A of 120V load or 400A of 120V load.

It is case #2 above. You can supply 400A of 120V load. You can't supply
a 400A 120V load, but with the load split between the legs you can
supply a total of 400A of 120V load, half of it from each leg. In that
case the hot legs run at 200A and the neutral is zero. You don't have
400A on any wire. I assume that is not a problem for you. That is all I
read Doug as saying. I agree.

Its gotta be a point-of-view problem.

--

I don;t see it as a point of view problem at all. * How many amps are
actually flowing in a 200 amp service to a house? * You draw an
imaginary plane and answer the question of how many amps are flowing
in and how many are flowing out. *If it is indeed 200 in, 200 out,
then that is 200 amps period. * You can have 200 amps flowing between
the two hots. * You can have 200 amps flowing between hot 1 and the
neutral. * You can have 200 amps flowing between hot 2 hot and *the
neutral, * *Any way you slice and dice it, it's still 200 amps.

If you can really have 400 amps of real current flow in the service,
then maybe Doug can answer this. * Suppose I have a 120 volt load that
takes 400 amps. * I connect it as a single 120V load to a 200 amp
service. *What happens?

A - Eveything works peechy keen, because 120V* 400amps = 48KVA, at the
service limit, so 400 amps flows just fine.

B - The service cable burns up, because the only way you can supply
that 400amps is by the load being balanced, in which case it appears
as a series load and the service is actually pulling 200amps through
one hot and back the other. * Which means that it would ONLY work if
you had two 200 amp, 120V loads connected to OPPOSIITE legs, and hence
acting as a SERIES circuit.



bud--- Hide quoted text -

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QUESTION...

In a service rated as a "200 Amp service"..

What are the numbers printed on the TWO main breakers?

Are they

A) 200/200?

or

B)100/100?

That is really the only question that needs to be answered .....

The rest should be obvious.

Mark

On Oct 26, 1:53*pm, Mark wrote:
On Oct 26, 1:44*pm, wrote:





On Oct 26, 12:45*pm, bud-- wrote:

wrote:
On Oct 25, 2:45 pm, (Doug Miller) wrote:

* ....
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?

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.. *

This is the only error I picked up. The supply voltage, as stated, is
120V in both cases. In the second case the 2 *60W bulbs would have to be
in parallel to give a load of 120W and 1A.
Assuming the light bulbs are linear resistances, with 60V across a 120V
bulb you would get 1/2 the rated current, or 1/4A which gives an
effective wattage in the 2nd case of 30W.

That isn't what you intended.

Yes, I agree. *good catch.

120W bulb - *120 ohms
60 W bulb *- 240 ohms
240W bulb - 60 ohms

So, in my example I should have used two 240 watt bulbs in series
which would be the same resistance as the 120watt bulb. * Actuallly, I
should have used a simple resistor or similar, because the resistance
of light bulbs is not a constant, temp dependent, etc.

But the example, corrected, still holds. * You would have 60 volts and
1 amp flowing across each bulb.

*....

Let me restate what I've said all along:

The arguments have gotten so twisted let me start here.

In a 200 amp service entering a house, there is a max of 200 amps of
actual current flowing. *You don't count current twice on a service
cable anymore than you would on an extension cord.

Here's a simple series of questions:

1 * I have a big 240V water heater that draws 200 amps and is
connected to a 200amp service via the two hot legs.

How much current is flowing in

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house

2 *Now instead of the single 240V water heater, I have two 120V water
heaters that draw 200 amps each. * *One is connected between hot leg 1
and neutral, the other between hot leg 2 and neutral.

How much current is flowing in:

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house

3 *Is the situation in #2 above an example of a parallel circuit or a
series circuit?

4 *I now disconnect the water heater that was connected to leg 2 in
the previous example. *You now have one 120V, 200 amp water heater
connected to leg 1 and neutral.

How much current is flowing in:

a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house

Everyone, I believe, has the same the answers (though I'm not sure what
"d" is).

I'm not so sure there is agreement as to the answers. * And if there
is agreement, then I don't see how there can be disagreement on how
many amps are flowing on the service cable. * *If you have X amps
coming in and X amps going out in a circuit, then that means X amps,
no?

The question from the OP, as I understand it, is with a panel feed at
200A 240V can you supply 200A of 120V load or 400A of 120V load.

It is case #2 above. You can supply 400A of 120V load. You can't supply
a 400A 120V load, but with the load split between the legs you can
supply a total of 400A of 120V load, half of it from each leg. In that
case the hot legs run at 200A and the neutral is zero. You don't have
400A on any wire. I assume that is not a problem for you. That is all I
read Doug as saying. I agree.

Its gotta be a point-of-view problem.

--

I don;t see it as a point of view problem at all. * How many amps are
actually flowing in a 200 amp service to a house? * You draw an
imaginary plane and answer the question of how many amps are flowing
in and how many are flowing out. *If it is indeed 200 in, 200 out,
then that is 200 amps period. * You can have 200 amps flowing between
the two hots. * You can have 200 amps flowing between hot 1 and the
neutral. * You can have 200 amps flowing between hot 2 hot and *the
neutral, * *Any way you slice and dice it, it's still 200 amps.

If you can really have 400 amps of real current flow in the service,
then maybe Doug can answer this. * Suppose I have a 120 volt load that
takes 400 amps. * I connect it as a single 120V load to a 200 amp
service. *What happens?

A - Eveything works peechy keen, because 120V* 400amps = 48KVA, at the
service limit, so 400 amps flows just fine.

B - The service cable burns up, because the only way you can supply
that 400amps is by the load being balanced, in which case it appears
as a series load and the service is actually pulling 200amps through
one hot and back the other. * Which means that it would ONLY work if
you had two 200 amp, 120V loads connected to OPPOSIITE legs, and hence
acting as a SERIES circuit.

bud--- Hide quoted text -

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QUESTION...

In a service rated as a "200 Amp service"..

What are the numbers printed on the TWO main breakers?

Are they

A) 200/200?

or

B)100/100?

That is really the only question that needs to be answered .....

The rest should be obvious.

Mark- Hide quoted text -

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in other words, is this:

http://homerepair.about.com/od/elect...elec_pnl_4.htm

considered to be a "100 amp service" or a "200 amp service?

Mark

wrote:
On Oct 26, 12:45 pm, bud-- wrote:
wrote:


....

Let me restate what I've said all along:

The arguments have gotten so twisted let me start here.

In a 200 amp service entering a house, there is a max of 200 amps of
actual current flowing. You don't count current twice on a service
cable anymore than you would on an extension cord.
Here's a simple series of questions:
1 I have a big 240V water heater that draws 200 amps and is
connected to a 200amp service via the two hot legs.
How much current is flowing in
a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house

2 Now instead of the single 240V water heater, I have two 120V water
heaters that draw 200 amps each. One is connected between hot leg 1
and neutral, the other between hot leg 2 and neutral.
How much current is flowing in:
a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house
3 Is the situation in #2 above an example of a parallel circuit or a
series circuit?
4 I now disconnect the water heater that was connected to leg 2 in
the previous example. You now have one 120V, 200 amp water heater
connected to leg 1 and neutral.
How much current is flowing in:
a - Hot leg 1
b - hot leg 2
c - neutral
d - the service cable entering the house

Everyone, I believe, has the same the answers (though I'm not sure what
"d" is).


I'm not so sure there is agreement as to the answers. And if there
is agreement, then I don't see how there can be disagreement on how
many amps are flowing on the service cable. If you have X amps
coming in and X amps going out in a circuit, then that means X amps,
no?

I don't understand Doug is saying there is 400A running in any wire.
And I am not saying there is.

The question from the OP, as I understand it, is with a panel feed at
200A 240V can you supply 200A of 120V load or 400A of 120V load.

It is case #2 above. You can supply 400A of 120V load. You can't supply
a 400A 120V load, but with the load split between the legs you can
supply a total of 400A of 120V load, half of it from each leg. In that
case the hot legs run at 200A and the neutral is zero. You don't have
400A on any wire. I assume that is not a problem for you. That is all I
read Doug as saying. I agree.

Its gotta be a point-of-view problem.

--

I don;t see it as a point of view problem at all. How many amps are
actually flowing in a 200 amp service to a house? You draw an
imaginary plane and answer the question of how many amps are flowing
in and how many are flowing out. If it is indeed 200 in, 200 out,
then that is 200 amps period. You can have 200 amps flowing between
the two hots. You can have 200 amps flowing between hot 1 and the
neutral. You can have 200 amps flowing between hot 2 hot and the
neutral, Any way you slice and dice it, it's still 200 amps.

In example #2 there is there 200A supplied to the 120V water heater on
leg 1.
And there is 200A supplied to the 120V water heater on leg 2.
Are you not supplying 400A of 120V load (split between leg 1 and leg 2)?

If you can really have 400 amps of real current flow in the service,
then maybe Doug can answer this.

I do not understand Doug ever said there was 400A in any wire. Rather
that there was 400A of total 120V load supplied - 1/2 on each leg.

Suppose I have a 120 volt load that
takes 400 amps. I connect it as a single 120V load to a 200 amp
service. What happens?

You don't connect it to one leg. You split the load in half and connect
one half leg 1 to neutral. You connect the other half from leg 2 to
neutral. (In this case you reconnect the single 400A 120V load as a 200A
240V load.)

If you have 40 - 10A 120V loads (400A total at 120V) you connect 20 of
them to leg 1 (200A). You connect the other 20 to leg 2 (200A). The
neutral current is zero. You have supplied 400A of 120V loads by
splitting it and connecting half to each leg.

A - Eveything works peechy keen, because 120V* 400amps = 48KVA, at the
service limit, so 400 amps flows just fine.

B - The service cable burns up, because the only way you can supply
that 400amps is by the load being balanced, in which case it appears
as a series load and the service is actually pulling 200amps through
one hot and back the other.


Which means that it would ONLY work if
you had two 200 amp, 120V loads connected to OPPOSIITE legs, and hence
acting as a SERIES circuit.

Which is how you connect it. I don't want to go back and reread the
thread - Doug's use of parallel may have not been the best. But I always
understood he was saying that half of a 400A load (200A) was connected
to leg 1 and the other half (200A) was connected to leg 2.

In answer to the OP's question - with a panel feed at 200A 240V can you
supply 400A of 120V load - the answer is yes.

I still think it is a point-of-view problem. You and Doug (and Smitty
and others?) all understand the underlying electrical.

--
bud--

In article , wrote:
On Oct 25, 2:45=A0pm, (Doug Miller) wrote:


How much power can be supplied by a 200A, 240V service? 24kVa, or 48kVA?

That's been asked an answered many times in this thread. It's 48,

Very good. Now divide 48kVA by 120V and tell me what you get.

In article , wrote:

You;ve asked that question multiple times and it's always been
answered the same: 48KVA

Now divide 48kVA by 120V and tell me what you get.

If all the loads supplied by that service are 120V loads (e.g. blender,
toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do you get
when you divide that maximum power by 120V?

If it's a balanced load, you get 400 amps

Which is exactly what I've been telling you for the last three days. Glad you
finally figured it out.

On Mon, 26 Oct 2009 03:08:49 GMT, (Doug Miller)
wrote:

In article , Sam E wrote:
[snip]


You have a SERIES circuit (considering that the neutral is effectively
disconnected).

[snip]

Wrong. The neutral is "effectively disconnected" *only* if the loads on the
two legs are exactly the same.

Which they are (either in the 200A+200A example or the 1A+1A one).

And that almost never happens in real life, either....

True, although it happens in examples, such as the ones used here.


The two legs function as two parallel circuits
with respect to 120V loads.

In a parallel circuit BOTH ends of the loads are connected together
(or at least to identical voltages). Neither is true here.

Wrong -- both are true.

IF those 2 legs have identical voltages, the difference between them
is 0 (that's what "identical" means). In that case, 120V loads should
be OK but 240V loads would get nothing.


Obviously they are indeed in series WRT 240V
loads.

Strangely, I get the idea that you actually know this stuff.

In this 200A service there are THREE current-carrying conductors.
Each of these conductors is of the proper size to carry 200A. OK so
far?

OK

You say (when this service is fully loaded) that two of these
conductors is carrying 200A (for a total of 400A, as you say).

400A @ 120V, or 200A @ 240V, yes.

That's some strange reality. In this one voltage and current are
different things, and you can't change one into another with
arithmetic.

There is still no 400A at any voltage.


Then where is that 400A going? The only remaining conductor is the
neutral, a big enough conductor for 200A (yes, this 400A was at 120V
but current is still current and voltage doesn't change the
conductor's current capacity).

Somehow I'm imagining a bridge that can handle 200 cars per minute,
but that can be 400 if half the cars are blue :-)

Cute. Just answer these questions; assume a 240V 200A service.


I notice you ignored mine. You have yet to show any non-imaginary
location of that 400A.

What is the maximum power that service can provide?


48KW. Of course we were talking about CURRENT.

If all the loads supplied by that service are 120V loads (e.g. blender,
toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do you get
when you divide that maximum power by 120V?

That would be 400A. Of course that's only in your imagination since
the math is invalid (120V is obtained by splitting the service into 2
separate halves, each of which is only 24KW).

In article , Sam E wrote:

If all the loads supplied by that service are 120V loads (e.g. blender,
toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do you get
when you divide that maximum power by 120V?

That would be 400A.

Exactly so.

Of course that's only in your imagination since
the math is invalid (120V is obtained by splitting the service into 2
separate halves, each of which is only 24KW).

200A each. Total of 400A of 120V loads -- as you said.

On Oct 23, 10:34*pm, (Doug Miller) wrote:
In article , JIMMIE wrote:

On Oct 23, 9:41=A0am, bud-- wrote:
JIMMIE wrote:

You shouldnt have more than 160 amps on any one leg or 80% of 200..

As Doug has probably been saying, the 80% limit is for continuous loads
(over 3 hours). Major loads in a house are not likely continuous. A
circuit breaker can operate at its full capacity, but may trip if at
full capacity for over 3 hours.

Its doubtfull you would ever pull more than 100 amps on a house wired
with a 200 amp panel. Worse case in my house would be WELDER, HVAC,
OVEN, and SPA running all at once.

Exactly. So why do you keep talking about the 80% rule? It doesn't apply.

Of course if wife and daughter are
both doing their hair at the same time that may put me over the top.

Do they take three hours to dry their hair? While the welder, HVAC, oven and
spa are all running? For three hours?

The 80% rule applies _only_ to continuous loads -- which is clearly and
specifically defined in the Code.

It seemed like it should in this case per the OP's description .
What's he doing, growing pot in his attic? Even if technically an
installation is residential commercial rules should apply if the
situation warrants it. I would say the described situation could fit
such a case.

Jimmie

On Oct 26, 10:37*pm, (Doug Miller) wrote:
In article , Sam E wrote:
If all the loads supplied by that service are 120V loads (e.g. blender,
toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do you get
when you divide that maximum power by 120V?

That would be 400A.

Exactly so.

Of course that's only in your imagination since
the math is invalid (120V is obtained by splitting the service into 2
separate halves, each of which is only 24KW).

200A each. Total of 400A of 120V loads -- as you said.

Where in the box can you measure 400 amps? If the panel is controlling
48KW there will be no current on the neutral because the currents will
be balanced. The current that flows through one half of the breaker is
the same current that flows through the other half of the breaker. In
this case what you have is two 200 amp breakers in series. Doug you
have more current coming into the box than going out and that shouldnt
happen.

"JIMMIE" wrote in message
...
On Oct 26, 10:37 pm, (Doug Miller) wrote:
In article , Sam E
wrote:
If all the loads supplied by that service are 120V loads (e.g. blender,
toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do
you get
when you divide that maximum power by 120V?

That would be 400A.

Exactly so.

Of course that's only in your imagination since
the math is invalid (120V is obtained by splitting the service into 2
separate halves, each of which is only 24KW).

200A each. Total of 400A of 120V loads -- as you said.

Where in the box can you measure 400 amps? If the panel is controlling
48KW there will be no current on the neutral because the currents will
be balanced. The current that flows through one half of the breaker is
the same current that flows through the other half of the breaker. In
this case what you have is two 200 amp breakers in series. Doug you
have more current coming into the box than going out and that shouldnt
happen.

The power is coming in from a transformer secondary winding that is
center-tapped. Let's call the 3 wires
Line 1, the neutral & Line 2 (seee the link below that shows a transformer
secondary at the bottom of the page). When you put 120V loads across Line 1
& neutral, they are independent of Line 2. In effect, you're only using half
of the transformer secondary, so you're only going thru the Line 1 half of
the main breaker. The current path is from the Line 1 side of the secondary
winding, thru the Line 1 side of the main breaker, thru the load, and back
thru the neutral to the Line 1 half of the secondary winding. If you also
put a 120V load across Line 2 and the neutral, then the current path is from
the Line 2 side of the secondary winding thru the Line 2 side of the main
breaker, thru the load, and back thru the neutral (in the opposite direction
of current flow of the Line 1 current thru the neutral) and back to the Line
2 side of the secondary winding. Both loads form their own circular loops
that are independent of each other, except for sharing the neutral (in
opposite directions) to complete their separate circuits. Here is a great
explanation of the transformer secondary, using the battery analogy which
the author (not me) originally designed to show balanced loads, but is also
useful in showing how 120V loads form independent circuits on each side of
the secondary. You can even close the various switchs and see the effect.

http://home.comcast.net/~ronaldrc/wsb/ax.htm

On Oct 22, 1:02*pm, "JayB" wrote:
This came up elsewhere and I am just curious about what the answer is.

If someone has a main service panel with a 200-amp main breaker, how many
amps of service can that panel actually service?

I am probably not wording this correctly, but I thought that I remember
something about a 200-amp main breaker actually being okay for 400 amps of
service since there are two separate circuits coming in (a 240-volt service
split into two 120-volt circuits in the panel box).

The answer is obvious; 200 amps. Although one working current
recommendation is to not exceed (I guess that's at any one time) some
80% of the maximum capacity. So say 160 amps.

It's rather like saying how many passengers can a 60 seater bus carry
(seated of course)!

The wire connections, bus bars (to which the individual circuit
breakers attach) are rated for 200 amps. Do not exceed.
BTW 200 amps at 230 volts is 230 x 200 = 46,000 watts (46
kilowatts).And 80% of that is about 37 kilowatts. That's usually
plenty for all but the biggest homes. To get maximum capability that
load should be balanced over the two 115 volt legs. Because if all the
loads were on only one leg the maximum capacity would be 115 x 200 =
23,000 watts (23 kilowatts) and 80% of that is about 18 -19 kilowatts.

"Steve N." wrote in message
...

"JIMMIE" wrote in message
...
On Oct 26, 10:37 pm, (Doug Miller) wrote:
In article , Sam E
wrote:
If all the loads supplied by that service are 120V loads (e.g. blender,
toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do
you get
when you divide that maximum power by 120V?

That would be 400A.

Exactly so.

Of course that's only in your imagination since
the math is invalid (120V is obtained by splitting the service into 2
separate halves, each of which is only 24KW).

200A each. Total of 400A of 120V loads -- as you said.

Where in the box can you measure 400 amps? If the panel is controlling
48KW there will be no current on the neutral because the currents will
be balanced. The current that flows through one half of the breaker is
the same current that flows through the other half of the breaker. In
this case what you have is two 200 amp breakers in series. Doug you
have more current coming into the box than going out and that shouldnt
happen.

The power is coming in from a transformer secondary winding that is
center-tapped. Let's call the 3 wires
Line 1, the neutral & Line 2 (seee the link below that shows a transformer
secondary at the bottom of the page). When you put 120V loads across Line
1 & neutral, they are independent of Line 2. In effect, you're only using
half of the transformer secondary, so you're only going thru the Line 1
half of the main breaker. The current path is from the Line 1 side of the
secondary winding, thru the Line 1 side of the main breaker, thru the
load, and back thru the neutral to the Line 1 half of the secondary
winding. If you also put a 120V load across Line 2 and the neutral, then
the current path is from the Line 2 side of the secondary winding thru the
Line 2 side of the main breaker, thru the load, and back thru the neutral
(in the opposite direction of current flow of the Line 1 current thru the
neutral) and back to the Line 2 side of the secondary winding. Both loads
form their own circular loops that are independent of each other, except
for sharing the neutral (in opposite directions) to complete their
separate circuits. Here is a great explanation of the transformer
secondary, using the battery analogy which the author (not me) originally
designed to show balanced loads, but is also useful in showing how 120V
loads form independent circuits on each side of the secondary. You can
even close the various switchs and see the effect.

http://home.comcast.net/~ronaldrc/wsb/ax.htm

I need to make a correction - the Line 2 current flow would be down the
neutral, thru the load, up thru the Line 2 half of the breaker, back to the
Line 2 side of the transformer. The currents flow in the same direction thru
the transformer secondary "halves", and in opposite directions thru the
neutral.

JIMMIE wrote:

Where in the box can you measure 400 amps? If the panel is controlling
48KW there will be no current on the neutral because the currents will
be balanced. The current that flows through one half of the breaker is
the same current that flows through the other half of the breaker. In
this case what you have is two 200 amp breakers in series. Doug you
have more current coming into the box than going out and that shouldnt
happen.

Think heat.

On Oct 27, 7:46*am, "HeyBub" wrote:
JIMMIE wrote:

Where in the box can you measure 400 amps? If the panel is controlling
48KW there will be no current on the neutral because the currents will
be balanced. The current that flows through one half of the breaker is
the same current that flows through the other half of the breaker. In
this case what you have is two 200 amp breakers in series. Doug you
have more current coming into the box than going out and that shouldn't
happen.

Think heat.

LOL

On Oct 26, 7:18*pm, (Doug Miller) wrote:
In article , wrote:

On Oct 25, 2:45=A0pm, (Doug Miller) wrote:

How much power can be supplied by a 200A, 240V service? 24kVa, or 48kVA?

That's been asked an answered many times in this thread. *It's 48,

Very good. Now divide 48kVA by 120V and tell me what you get.

Again, this has been answered here repeatedl, so I don't see why you
keep asking.. One more time, it's obviously 400 amps.

Also, you only get those 400 amps if the load is balanced so that it
appears as a series load. The 200 amp current flows in one hot and
out the other. If you had a single 120V 400 amp load, it would sit
between one hot leg and neutral, where the capacity is limited to 200
amps and the cables would melt. Gee, I wonder why? Could it be
because the actual current in a 200 amp service circuit is only 200
amps?

You can divide and get any answer you want. I could divide 48KVA by
10volts and get 4800 amps. So a 200 amp service could support a
total 4800 amp, 10 volt load too. But how much max current is
actually flowing in the service cable entering the house? Exactly
the same as always, 200 amps. If you believe otherwise, please tell
us what currents are flowing in each of the three conductors.

On Oct 27, 9:03*am, JIMMIE wrote:
On Oct 27, 7:46*am, "HeyBub" wrote:

JIMMIE wrote:

Where in the box can you measure 400 amps? If the panel is controlling
48KW there will be no current on the neutral because the currents will
be balanced. The current that flows through one half of the breaker is
the same current that flows through the other half of the breaker. In
this case what you have is two 200 amp breakers in series. Doug you
have more current coming into the box than going out and that shouldn't
happen.

Think heat.

LOL

Jimmie: I think the reason this thread has gone so long is that some
do not really understand current flow, especially AC (Alternating
Current) single phase and may be confusing current flow (amperes) with
power (watts/kilowatts).

In some countries also they have only two wires coming into a domestic
service (plus ground/earth). So they have a concept of only the two
wires of a single phase 230 volt service. One of which is neutral
(essentially at zero volts!) and the other at 230 volts (often 50
hertz) to neutral and ground. the size of those dermines the ampere
capacity of the service.

Was looking at distribution along a street in Malta; which was
attached to the face of the buildings. It comprised four wires. One of
which was ground/earth. I think it was green? One of the remaining
three was neutral. The other two were most likely 230+ and 230- as it
were of a single phase. Or they might have been two phases of a a 3
phase delta/star transformer sub-station secondary at end of the
street. The house services along the street were connected alternately
to these last two. In other words all services were two wire single
phase 230 volt, plus a ground/earth.

Again in one of the Gulf States it was also essentially 230 volts 50
hertz. BUT; in that instance there were the three phases and neutral
etc. coming into every residence unit and the circuit breaker panel or
CU (Consumer Unit) had three sections one for each phase. The fact
that there were some seven large 230 volt 50 hertz AC units in each
unit probaly required a heavy service! Residentially didn't see any 3
phase equipment although it could have been hooked up. It was mainly
UG.

Other areas of the world may vary; in Sri Lanka for example it was
hard to tell what was going on viewing some of the lash-ups on some of
the service poles!

Anyway the point of all this is that it's best to understand, no
matter where one is, what the electrical service arrangement is. Also
that with two wires (plus ground) there can be no
doubt .................. a 200 amp service (or whatever it's rated) is
just that, 200 amps.

No more (unless overloaded) no less (subject to the recommended 80%
rule for prolonged use). Nothing magic about it!

On Oct 26, 4:36*pm, bud-- wrote:
*Suppose I have a 120 volt load that
takes 400 amps. * I connect it as a single 120V load to a 200 amp
service. *What happens?

You don't connect it to one leg. You split the load in half and connect
one half leg 1 to neutral. You connect the other half from leg 2 to
neutral. (In this case you reconnect the single 400A 120V load as a 200A
240V load.)


That was precisely my point. That to support a 400 amp 120V load,
the load must be perfectly balanced. And that is because only a max
of 200 amps is flowing in the service cable and the 400 amp, 120V load
must appear as two 200 amp, 120V loads in SERIES.

It's a very basic and simple electrical question as to how many amps
are flowing in that 200 amp service cable and it's 200 amps. You
could support all kinds of loads of varying voltages off it, including
400 amps at 120V, provided the load is perfectly balanced. I could
further break it down to support a total load of 800 amps at 60volts,
etc. That doesn't change the physical current in the service cable
from being limited to 200 amps? If you put a current meter on it you
would measure 200 amps flowing into the house, 200 amps flowing out.

Do we agree?

And none of that has anything to do with claims that were made here
that you get 400 amps because there is a second conductor. Or that
the service is a parallel circuit. I showed in the box with light
bulbs how the exact same thing can be done running various loads/
voltages off just a 2 wire 120V outlet.







If you have 40 - 10A 120V loads (400A total at 120V) you connect 20 of
them to leg 1 (200A). You connect the other 20 to leg 2 (200A). The
neutral current is zero. You have supplied 400A of 120V loads by
splitting it and connecting half to each leg.

A - Eveything works peechy keen, because 120V* 400amps = 48KVA, at the
service limit, so 400 amps flows just fine.

B - The service cable burns up, because the only way you can supply
that 400amps is by the load being balanced, in which case it appears
as a series load and the service is actually pulling 200amps through
one hot and back the other. *
Which means that it would ONLY work if
you had two 200 amp, 120V loads connected to OPPOSIITE legs, and hence
acting as a SERIES circuit.

Which is how you connect it. I don't want to go back and reread the
thread - Doug's use of parallel may have not been the best. But I always
understood he was saying that half of a 400A load (200A) was connected
to leg 1 and the other half (200A) was connected to leg 2.

In answer to the OP's question - with a panel feed at 200A 240V can you
supply 400A of 120V load - the answer is yes.

I still think it is a point-of-view problem. You and Doug (and Smitty
and others?) all understand the underlying electrical.

--
bud--- Hide quoted text -


I'm not so sure, as I have yet to hear Doug acknowledge that there is
actually only a 200 amp current flowing in that service cable. When
asked that by others he has replied with answers that try to link it
to voltage, ie 200 amps at 240V or 400 amps at 120V. And that is
simply wrong. Amps and voltage are two different things. There is
never more than 200 amps flowing in that service cable circuit.

On Oct 27, 2:37*am, "Steve N." wrote:
"Steve N." wrote in message

...







"JIMMIE" wrote in message
...
On Oct 26, 10:37 pm, (Doug Miller) wrote:
In article , Sam E
wrote:
If all the loads supplied by that service are 120V loads (e.g. blender,
toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do
you get
when you divide that maximum power by 120V?

That would be 400A.

Exactly so.

Of course that's only in your imagination since
the math is invalid (120V is obtained by splitting the service into 2
separate halves, each of which is only 24KW).

200A each. Total of 400A of 120V loads -- as you said.

Where in the box can you measure 400 amps? If the panel is controlling
48KW there will be no current on the neutral because the currents will
be balanced. The current that flows through one half of the breaker is
the same current that flows through the other half of the breaker. In
this case what you have is two 200 amp breakers in series. Doug you
have more current coming into the box than going out and that shouldnt
happen.

The power is coming in from a transformer secondary winding that is
center-tapped. Let's call the 3 wires
Line 1, the neutral & Line 2 (seee the link below that shows a transformer
secondary at the bottom of the page). When you put 120V loads across Line
1 & neutral, they are independent of Line 2. In effect, you're only using
half of the transformer secondary, so you're only going thru the Line 1
half of the main breaker. The current path is from the Line 1 side of the
secondary winding, thru the Line 1 side of the main breaker, thru the
load, and back thru the neutral to the Line 1 half of the secondary
winding.

Agree.


If you also put a 120V load across Line 2 and the neutral, then
the current path is from the Line 2 side of the secondary winding thru the
Line 2 side of the main breaker, thru the load, and back thru the neutral
(in the opposite direction of current flow of the Line 1 current thru the
neutral) and back to the Line 2 side of the secondary winding. Both loads
form their own circular loops that are independent of each other, except
for sharing the neutral (in opposite directions) to complete their
separate circuits.

Don't agree with this. If the second load on line 2 is equal to the
load already on line 1, then the current flow is in on line 1 and back
out on line 2. No current flows in the neutral.

If the second load on line 2 were half the size of the load on line 1,
then half the current from line 1 would flow back out on line 2 and
half the current from line 1 would flow back out the neutral.


The key here is look at that service cable coming from the transformer
and you have a circuit running a max of 200 amps. Agree?

terry wrote:
On Oct 22, 1:02 pm, "JayB" wrote:
This came up elsewhere and I am just curious about what the answer is.

If someone has a main service panel with a 200-amp main breaker, how many
amps of service can that panel actually service?

I am probably not wording this correctly, but I thought that I remember
something about a 200-amp main breaker actually being okay for 400 amps of
service since there are two separate circuits coming in (a 240-volt service
split into two 120-volt circuits in the panel box).

The answer is obvious; 200 amps.

The answer is obvious; 400 amps.

Although one working current
recommendation is to not exceed (I guess that's at any one time) some
80% of the maximum capacity. So say 160 amps.

Don't know about Canada, but in the US 80% only applies to "continuous
loads" (over 3 hours). In a house service, if you could get a 200 amp
peak it wouldn't last long. Loads cycle on and off. It is called
"diversity". Because of diversity the service wires (in the US) can
usually be 'undersized' with a residential derate. Can't do that in
commercial, where you turn on lights and they are on all day long
("continuous").


The wire connections, bus bars (to which the individual circuit
breakers attach) are rated for 200 amps. Do not exceed.
BTW 200 amps at 230 volts is 230 x 200 = 46,000 watts (46
kilowatts).And 80% of that is about 37 kilowatts. That's usually
plenty for all but the biggest homes. To get maximum capability that
load should be balanced over the two 115 volt legs.

And when you balance the load over the two 115 volt legs you get - lets
see - 46,000 watts divided by 115 volts - um - 400 amps of 115 volt
load. Even in Canada. That is what the OP asked.

--
bud--

In article , wrote:
On Oct 26, 7:18=A0pm, (Doug Miller) wrote:
In article .=
com, wrote:

On Oct 25, 2:45=3DA0pm, (Doug Miller) wrote:

How much power can be supplied by a 200A, 240V service? 24kVa, or 48kVA?

That's been asked an answered many times in this thread. It's 48,

Very good. Now divide 48kVA by 120V and tell me what you get.

Again, this has been answered here repeatedl, so I don't see why you
keep asking.. One more time, it's obviously 400 amps.

Which is exactly what I've been telling you for the last four days: a 200A
240V service will support 400A of 120V loads. I'm glad you finally figured it
out.