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).
It all depends on voltage. A 220 amp service can in theory (you are not
supposed to use more than 80%) supply 200 amps at 240 volts OR 400 amps at
120 volts or any combination of the above.
Not so. You misunderstand the 80% rule.
plus the 200 amp dual breaker can and will carry a percentage more
indefinetely
I had a friend who had the largest outdoor light display in the area,
the power company loved him:(
checking the legs of his main service, it exceeded 200 amps on either
side.
he couldnt run his dishwasher, washer dryer, or even a hair dryer as
his wife found out when the lights were on..........
her hair dryer blacked out the total home.
when his kids got bigger he quit decorating......... but geez it was
beautiful
Aside from the 80% rule, you can't get 400 amps out of a 200amp
service. The service consists of two hots, and a neutral. That
means with a 200 amp service you can get 200 amps at 240V flowing
between the two hots. Or you could get say 150 amps at 240V plus 50
amps at 120V. /In the latter case you have 200 amps flowing on one
hot, 150 on the other hot, and 50 on the neutral.
>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.
> The service consists of two hots, and a neutral. That
>means with a 200 amp service you can get 200 amps at 240V flowing
>between the two hots. Or you could get say 150 amps at 240V plus 50
>amps at 120V. /In the latter case you have 200 amps flowing on one
>hot, 150 on the other hot, and 50 on the neutral.
Ummm....no. You could have up to 150A at 240V plus *100A* at 120V -- and if
the loads are distributed evenly across the two legs, the current in the
neutral is zero.
And, to make it perfectly clear, _only_ the two "hots" are on
overcurrent protection; the neutral is not.
--
That's what I thought -- that 200 amps at 240 volts is basically 400 amps
available at 120 volts. Or, for example, if 50 of the 200 amps were for a
240 volt circuit, that would leave 150 amps at 240 which could be 300 amps
at 120 volts.
"Doug Miller" <spam...@milmac.com> wrote in message
news:hbqe8e$2nq$1...@news.eternal-september.org...
One other complicating factor is the 125A max branch circuit limitation.
Not an issue in normal residential application of course as few people
have single loads over 125A, but something to keep in mind when feeding
subpanels.
The difference is that you can't run a single 120V load at a full 400
amps. But you could run two different 120V loads at 200 amps.
> One other complicating factor is the 125A max branch circuit
> limitation.
The only limitation here is in the breakers for your panel. Larger
breakers may be available; they often take up more space than normal
in the panel, so as to have multiple connections to the same busbar.
Cheers, Wayne
People just playing with words!
Since: Power = voltage multiplied by amperage. For example if one has
individual 20 amp 115 volt circuits the maximum power each could carry
is 115 x 20 = 2,300 watts.
A 15 amp lighting circuit, 115 x 15 = 1725 watts.
Similarly (ignoring the 80% rule for the moment) the maximum power
that a 200 amp (Standard North American 115 - 0 - 115) domestic
service can carry is 200 x 230 = 46,000 watts.
It is not possible for all the power could be loaded 'all on one 115
volt leg/side', as 115 x 400 = 46,000 watts. This would be rather like
saying one could put the total weight of a ten ton truck ALL on one
set of wheels! Or hiring two taxis to carry ten passengers, but then
putting all ten passengers in one taxi, with none in the other!
That's also why domestic loads are 'supposed' to be balanced/
distributed' across both legs. In practice rarely operating in most
situations at anything close to maximum loading. So balance not often
an issue.
A domestic service double pole main circuit protects both legs of the
incoming service. Once the trip limit of the breaker (200 amps say)
exceeded, on either leg it would operate thus disconnecting both 115
volt legs.
You shouldnt have more than 160 amps on any one leg or 80% of 200..
Jimmie
<hal...@aol.com> wrote in message
news:f7d40e24-42f2-4aa4...@o36g2000vbl.googlegroups.com...
http://www.youtube.com/watch?v=8qc_RYm0ylA&NR=1
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
<hal...@aol.com> wrote in message
news:f7d40e24-42f2-4aa4...@o36g2000vbl.googlegroups.com...
I had a friend who had the largest outdoor light display in
http://www.youtube.com/watch?v=8qc_RYm0ylA&NR=1
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
<hal...@aol.com> wrote in message
news:f7d40e24-42f2-4aa4...@o36g2000vbl.googlegroups.com...
I had a friend who had the largest outdoor light display in
griswald is what my neighbor was called reportedly by everyone he
knew.
he lit up the neighborhood, and his power bill:( collected donations
for salvation army and created sometimes massive traffic jams, after
his display was featured on news.
i alwasys expected him to blow the local transformer..........
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.
What you are arguing is like saying a resistor that has 1 amp flowing
in it is actually carrying 2 amps, because 1 amp goes in and one amp
goes out.
>
> > The service consists of two hots, and a neutral. That
> >means with a 200 amp service you can get 200 amps at 240V flowing
> >between the two hots. Or you could get say 150 amps at 240V plus 50
> >amps at 120V. /In the latter case you have 200 amps flowing on one
> >hot, 150 on the other hot, and 50 on the neutral.
>
> Ummm....no. You could have up to 150A at 240V plus *100A* at 120V -- and if
> the loads are distributed evenly across the two legs, the current in the
> neutral is zero.
That is not true. If you have 150A running at 240V then you have
150A coming in on one hot, 150A going out on the other hot during each
half cycle and zero flowing through the neutral. The next half
cycle, it reverses. If you now add another 50 amps between one hot
and neutral, you now have 200A running through one hot, `150 amps
through the other hot, and 50 amps through the neutral. There is
nowhere for your extra 50 amps to come from to give you 250amps The
max current flowing is still limited to 200 amps.
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.
--
bud--
Do you expect to actually draw 200 amps at once, or are you adding up
the amperage value of all the circuit breakers?
>
>You shouldnt have more than 160 amps on any one leg or 80% of 200..
Incorrect. You do not understand the "80% rule". The rule applies only to
"continuous loads" which is defined by the Code as maximum current for a
period of three hours or more.
200 amps on _each leg_. It's a total of (up to) 400 amps at 120V.
>
>What you are arguing is like saying a resistor that has 1 amp flowing
>in it is actually carrying 2 amps, because 1 amp goes in and one amp
>goes out.
It's not at all the same. You are failing to consider that the two legs of a
residential service can be treated as two *separate* parallel 120V circuits.
>>
>> > The service consists of two hots, and a neutral. That
>> >means with a 200 amp service you can get 200 amps at 240V flowing
>> >between the two hots. Or you could get say 150 amps at 240V plus 50
>> >amps at 120V. In the latter case you have 200 amps flowing on one
>> >hot, 150 on the other hot, and 50 on the neutral.
>>
>> Ummm....no. You could have up to 150A at 240V plus *100A* at 120V -- and if
>> the loads are distributed evenly across the two legs, the current in the
>> neutral is zero.
>
>That is not true. If you have 150A running at 240V then you have
>150A coming in on one hot, 150A going out on the other hot during each
>half cycle and zero flowing through the neutral. The next half
>cycle, it reverses. If you now add another 50 amps between one hot
>and neutral, you now have 200A running through one hot, `150 amps
>through the other hot, and 50 amps through the neutral.
Right so far...
>There is
>nowhere for your extra 50 amps to come from
Sure there is: the other hot leg still has an extra 50A capacity.
> to give you 250amps
Ahh, _there_ is the source of your misconception.
The neutral carries only the unbalanced current. When the other hot leg
carries 200A as well, the current in the neutral _drops to zero_.
> The
>max current flowing is still limited to 200 amps.
Suppose that the residence has no 240V loads of any sort -- gas furnace, gas
WH, gas dryer, gas stove, no large power tools, no double-pole breakers, every
circuit in the panel is a 120V circuit.
Do you maintain that the maximum power that could be drawn from this service
is 200A @ 120V = 24kVA?
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
<hal...@aol.com> wrote in message
news:00ccc6b0-18f7-4efa...@q14g2000vbi.googlegroups.com...
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. Of course if wife and daughter are
both doing their hair at the same time that may put me over the top.
Jimmie
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.
>In article <9d65d12b-f49b-4fd4...@p15g2000vbl.googlegroups.com>, tra...@optonline.net wrote:
>>On Oct 22, 4:10=A0pm, spamb...@milmac.com (Doug Miller) wrote:
>>> In article <eac71d20-b0a7-49ff-970c-7068c6290...@l35g2000vba.googlegroups=
>>..com>, trad...@optonline.net 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.
200A @ 120V on leg 1, 200A @ 120V on leg 2.
>
>Being able to add to numbers* doesn't mean reality works that way.
Actually, it does.
>
>[snip]
>
>* - Actually, that's incorrect too. The addends are out of phase, so
>200 + 200 = 0.
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.
Yes, you are right on that point and I was wrong.
>
> > to give you 250amps
>
> Ahh, _there_ is the source of your misconception.
>
> The neutral carries only the unbalanced current. When the other hot leg
> carries 200A as well, the current in the neutral _drops to zero_.
>
> > The
> >max current flowing is still limited to 200 amps.
>
> Suppose that the residence has no 240V loads of any sort -- gas furnace, gas
> WH, gas dryer, gas stove, no large power tools, no double-pole breakers, every
> circuit in the panel is a 120V circuit.
>
> Do you maintain that the maximum power that could be drawn from this service
> is 200A @ 120V = 24kVA?- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -
The issue here is what defines the current at the service. In a 200
amp service there is only 200 amps of actual physical current running
through the service conductors. The conductors are sized for 200
amps, not 400 amps.
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.
That's what I meant when I said a 200 amp service cannot supply 400
amps of current.
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.
Consider a house with only 120V loads, no 240V circuits anywhere, and 200A
service. Suppose that one leg of the service is fully loaded, and the other
leg is unloaded. I think we'd both agree that the power being drawn is 200A at
120V, right?
Now fully load the other leg too.
> In article
> <5aaa3012-faa6-43f2...@d34g2000vbm.googlegroups.com>,
> tra...@optonline.net 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?
>
*Immediately* above your two questions, he answered them both, Doug.
There isn't really so much disagreement going on, it's just that y'all
aren't paying attention to what the others are saying.
I think the problem is that people aren't paying attention to what the
other is saying. ;)
R
He doesn't understand the implications of what he wrote, though, which is why
I'm emphasizing it.
>There isn't really so much disagreement going on, it's just that y'all
>aren't paying attention to what the others are saying.
Rather, vice versa. A 200A residential service supplies up to 200A _at 240V_.
This is _exactly_ equivalent to 400A at 120V -- which is precisely what you
have if each leg of the service is fully loaded at 120V.
> A 200A residential service supplies up to 200A _at 240V_. This is
> _exactly_ equivalent to 400A at 120V -- which is precisely what you
> have if each leg of the service is fully loaded at 120V.
There are a couple small differences between 400A worth of 120V loads
balanced on the two legs of a 240/120V supply, and 400A of loads on a
120V supply. First, in the former case the biggest 120V load you can
handle (without a transformer) is 200A, while in the latter case you
can handle a 400A 120V load. Second, the voltage drop on the supply
is different. V = I^2 * R, where I is 200A in the first case, and
400A in the second case.
Cheers, Wayne
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. 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.
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. If you want to get techical, since it's AC,
the current direction switches each cycle.
Kapisch?
>
> >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.
They are NOT parallel circuits. That would imply that each has it's
own seperate return path. They do not. The return path is through
the other hot conductor for the balanced part of the load and through
the shared neutral for the unbalanced portion. Again, at any point
in time there is only 200 amps moving through that service going into
the home, which is why it's called a 200 amp service.
>
> Consider a house with only 120V loads, no 240V circuits anywhere, and 200A
> service. Suppose that one leg of the service is fully loaded, and the other
> leg is unloaded. I think we'd both agree that the power being drawn is 200A at
> 120V, right?
Yes
>
> Now fully load the other leg too.- Hide quoted text -
>
And now you have 200 amps flowing from one hot and back on the other
hot. Zero flows through the neutral. Hence, again, it's only a
200 amp total current moving through the service.
[...]
>> 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.
> 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.
> If you want to get techical, since it's AC,
>the current direction switches each cycle.
>
>Kapisch?
I "kapisch" that you don't understand this.
>
>>
>> >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.
>
>They are NOT parallel circuits. That would imply that each has it's
>own seperate return path. They do not. The return path is through
>the other hot conductor for the balanced part of the load and through
>the shared neutral for the unbalanced portion. Again, at any point
>in time there is only 200 amps moving through that service going into
>the home, which is why it's called a 200 amp service.
Suppose that each one had its own separate return. Does that change your
answer?
>
>> Consider a house with only 120V loads, no 240V circuits anywhere, and 200A
>> service. Suppose that one leg of the service is fully loaded, and the other
>> leg is unloaded. I think we'd both agree that the power being drawn is 200A at
>> 120V, right?
>
>Yes
>>
>> Now fully load the other leg too.
>
>And now you have 200 amps flowing from one hot and back on the other
>hot. Zero flows through the neutral. Hence, again, it's only a
>200 amp total current moving through the service.
So, according to your reasoning, since it's "only a 200 amp total current",
then 200A at 120V on only one leg of the service is the same as 200A at 120V
on *each* leg of the service.
....with a common neutral wire which must provide a return path for both
circuits.
> 200A flowing in each of two parallel circuits is 400A total, not 200A.
As long as the neutral wire is rated for an amperage capacity of
400A...if it's not, and you try feeding 400 amps through a wire only
rated for 200A max, what do you think will happen? ;-)
>>
>>The two legs of a residential electrical service are, in effect, two parallel circuits.
>
>.....with a common neutral wire which must provide a return path for both
>circuits.
>
>> 200A flowing in each of two parallel circuits is 400A total, not 200A.
>
>As long as the neutral wire is rated for an amperage capacity of
>400A...if it's not, and you try feeding 400 amps through a wire only
>rated for 200A max, what do you think will happen? ;-)
You badly misunderstand how this works. In a 240/120 residential service, the
neutral carries only the unbalanced current (the difference between the
currents in the hot legs, not their sum): if 50A is being drawn on one hot
leg, and 90A on the other, the neutral carries only 40A. If one hot leg is
carrying 200A, and the other 199A, the current in the neutral is *not* 399A --
it's 1A. And if both hot legs are loaded exactly equally, whether that's 1mA
each or 200A each, the current in the neutral is zero.
For 200A service, the neutral does *not* need to be rated for 400A. The most
it can ever carry -- if one hot leg is fully loaded, and the other is unused
-- is 200A, and if the loads are even halfway close to being balanced across
the two legs, most of the time the current in the neutral is far less than
that.
> 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.
At the time I read it a continuous power situation is the only thing
that made sense to me. Having the flu and taking codeine will change
ones sense quite a bit. Sorry, you are correct.
> In article
> <prestwhich-9F424...@newsfarm.iad.highwinds-media.com>, Smitty
> Two <prest...@earthlink.net> wrote:
> >In article <hc045a$83r$1...@news.eternal-september.org>,
> > spam...@milmac.com (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.
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, in a series circuit, the current is the same throughout the
circuit. You seem to be claiming otherwise.
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?
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.
>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?
>In article <5aaa3012-faa6-43f2...@d34g2000vbm.googlegroups.com>, tra...@optonline.net 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]
>In article <a5e64d7a-48be-4459...@e18g2000vbe.googlegroups.com>, tra...@optonline.net wrote:
>>On Oct 24, 2:17=A0pm, spamb...@milmac.com (Doug Miller) wrote:
>>> In article <5aaa3012-faa6-43f2-bd82-0afc8bc5f...@d34g2000vbm.googlegroups=
>>..com>, trad...@optonline.net 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]
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?
There's no current in the neutral if the loads are balanced.
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.
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.
>In article <4mt8e5dtu75qpt85h...@4ax.com>, Sam E <no.e...@all.invalid> wrote:
No current. I was replying to the person who claimed 400A.
>>
>>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
>>
>>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 :-)
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?
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
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
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
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!
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.
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.
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--
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.
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 -
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
in other words, is this:
http://homerepair.about.com/od/electricalrepair/ss/anat_elec_pnl_4.htm
considered to be a "100 amp service" or a "200 amp service?
Mark
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--
>>
>> 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.
>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.
>In article <j6v9e5hle5qps7s2v...@4ax.com>, Sam E <no.e...@all.invalid> 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).
>>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.
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
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.
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.
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.
Think heat.
LOL
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--
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.
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!
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.
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?
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.
Thank you. That's exactly what I've been saying all along.
Here's a circuit diagram of a fully loaded, balanced 200 amp service:
-------------- 240 volt source-----------
I I
a I I b
I I
I------------------2.4 ohmRes-----------I
I I
I-----1.2 ohmR-----1.2 ohmR--------I
How much current is flowing in the "service", which is through the
voltage source? 200 amps. It supporting one 240Volt 100 amp load
and two 120volt 100 amp loads. By every circuit concept I've ever
heard of there is but 2 amps flowing in the service cable here. Yet,
some would have you believe it 3 amps.
If we want to include the neutral then it looks like this:
+ -- + --
I------------120V----I-------120V---------
I I I
I I I
I I I
I-----1.2ohms------I--------1.2ohms---I
I I
I-------------------2.4 ohms---------------I
The service now consists of 3 wires. In this case, because it's
balanced no current is flowing in the neutral. You can unbalance it,
do anything you like and still with a 200 amp service there is only
200 amps flowing in, 200 amps flowing out. And it;s not a "parallel
circuit either as Doug has claimed.
That has never been in dispute. What has been is how many physical
amps are flowing in the service cable circuit of a 200 amp service?
Here's a hint: Try answering this simple physics question without
refering to voltage or power.
>Also, you only get those 400 amps if the load is balanced so that it
>appears as a series load.
You're right. If the the two 120V loads are perfectly balanced, then it's
the equivalent to two 120V 0.6 ohm loads in series across 240V each pulling
200 amps, and you can disregard the neutral or even disconnect it. The
neutral is there to
hold the voltage on each leg or side to 120V when the loads aren't perfectly
balanced.
>The 200 amp current flows in one hot and
>out the other.
True
> 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?
No, the main breaker would open long before any melting
>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?
A whole bunch for a few microseconds. A breaker isn't instantaneous.
Agree.
OK, you're right. If they're perfectly balanced. So lets make the Line
1-to-neutral load
a 200A load (0.6 ohms), and the Line 2-to-neutral load 199A (0.603 ohms).
Now we have an unbalanced current of
1 amp thru the neutral.So we have 200A thru one side of the breaker, and
199A thru the other side. So what's the total amperage now?? Is it 200A or
399A, or? It's all in how you look at it. In the end ,it's a matter of
total energy or kW.
200A x 120V=24000W & 199A x 120V= 23880W for a total of 47880W or 47.88kW
>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?
With a perfectly balanced load - yes, one circuit. With a slightly
unbalanced load - then, two circuits.
Yes, I agree, assuming there is one. In our hypothetical case I was
ignoring any breakers.
>
> >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?
>
> A whole bunch for a few microseconds. A breaker isn't instantaneous.
We have been discussing continous loads at the service max, not
transients. That 200 amp service can support a total load of 4800
amps at 10 volts, or 2400 amps at 20 volts. As I said before, you
can slice it and dice it anyway you want, but you still have 200 amps
max of current flowing in the service.
No, it not. Once again, the physical current in the service cable is
200 amps. You have 200 amps flowing IN on one hot, 199 flowing OUT
on the other hot and 1 amp flowing OUT on the neutral. The current
flowing in that circuit is 200 amps. You don't count current twice.
How much current is flowing in a simple 120W light bulb plugged into a
120Volt outlet? 1 amp. Now simply add another single wire in
parallel with one of those supplying the light bulb. The current
will be split now, with some part of it going via one wire, some via
the other. For sake of argument, let;s assume it just splits
evenly. So, now you have 1 amp coming in on one wire, 1/2 amp
leaving via one wire, 1/2 amp leaving via the second wire. How much
current is flowing in this "service" circuit to the light bulb?
There is no confusion, it's 1 amp.
It's a simple matter of applying Kirchoffs law.
> In the end ,it's a matter of
> total energy or kW.
> 200A x 120V=24000W & 199A x 120V= 23880W for a total of 47880W or 47.88kW
>
> >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?
>
> With a perfectly balanced load - yes, one circuit. With a slightly
> unbalanced load - then, two circuits.- Hide quoted text -
>
> - Show quoted text -
Balanced or unbalanced matters not a wit. There is still a current
of 200 amps coming and going either way. The only difference balance
makes is which PATH that 200 amp current takes.
200A thru each main-breakered leg - yes. But I'm not sure where the 4800A @
10V is coming from.
Do you think the transformer secondary windings will sustain at 4800A? Are
you now taliing about continuous or transient??
Here's a circuit diagram of a fully loaded, balanced 200 amp service:
-------------- 240 volt source-----------
I I
a I I b
I I
I------------------2.4 ohmRes-----------I
I I
I-----1.2 ohmR-----1.2 ohmR--------I
How much current is flowing in the "service", which is through the
voltage source? 200 amps. It supporting one 240Volt 100 amp load
and two 120volt 100 amp loads. By every circuit concept I've ever
heard of there is but 200 amps flowing in the service cable here.
Yet,
some would have you believe it 300 amps.
Umm...so you're saying that if you have a 200A load on Line1to neutral that
you're going to have 200A going thru both sides of the 200A breaker
regardless of the load on the Line 2 to neutral side??
What if you have a 200A load on the Line 1 to neutral side, and nothing
loading the Line 2 to neutral side? Are you still going to have 200A going
thru each "leg" of the main breaker?
L1 side L2 side
I000000000000000000000000000000000I The 00000s
represent trans. windings
I------120V----------I-------120V---------I
I I I
MB1= 200A main breaker Line 1 side
I I I
MB2= 200A main breaker Line 2 side
MB1 I MB2
I I I
I I I
I-----0.6ohms--------I------ ------I
There will be 200Amps down thru MB1 and thru the load and back up thru the
secondary winding using
one half of the transformer secondary winding.to form a circular loop..
There will be NO current thru MB2
because there is no current path.
>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.
Two 200A 120V loads in series makes a 200A 240V load.
>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
The only way you can get 400A out of a 200A service is with a step-down
transformer.
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>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.
Two 200A 120V loads in series makes a 200A 240V load.
>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
The only way you can get 400A out of a 200A service is with a step-down
transformer.
On Tue, 27 Oct 2009 08:27:24 -0700 (PDT), in alt.home.repair,
tra...@optonline.net wrote:
>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.
Two 200A 120V loads in series makes a 200A 240V load.
>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
The only way you can get 400A out of a 200A service is with a step-down
I think we are in agreement, except for perhaps one point.
From your previous post, you clearly agree that you can in fact have
two 120volt, 200 amp loads connected in series across the 240volt
service. That is a perfectly balanced load. You now have 200 amps
flowing in series through each load. In my world that is in fact
"supporting" 400 amps of 120volt load. Lets say I had forty 10 amp,
120volt heaters. I could could clearly put twenty of them between one
leg and neutral and twenty between the other leg and neutral and it
would work. You now have a fully loaded balanced service. There
is zero current flowing in the neutral and 200 amps flowing in the
service. It works because the loads on one side are connected in
series to the loads on the other side.
My whole point all along has been that the actual current in a 200
amps service is limited to 200 amps which clearly you agee with.
And it has nothing to do with "parallel circuits", or power, voltage
or anything else. It looks like the only difference we have is your
definition of "supporting loads" may be stricter than mine.
And I think all of us are still waiting for a simple answer from Doug
as to how many amps are actually flowing in a fully loaded 200 amp
service cable circuit. I've asked that several times now and still
have no answer, despite having fully answered all his questions.
--
> 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, otherwise my filters
Yes. You have a 3 wire service cable coming into the house. Use
Kirchoff's law and add up the current coming into the house at any
point in time under any conditions through that cable any you have a
max of 200 amps. Add up all the current leaving the house at the
same point in time and you have a max of 200 amps. In my world,
that's a 200 amp service. You don't measure 300, or 400 by counting
electrons twice.
And also, to support a max of 400 amps of 120volt load in the house
which is the hot topic, you have to have the special case where the
loads are perfectly balanced so that 200 amps is on each side. And
then you in fact have a SINGLE circuit with 200 amps flowing in on one
hot leg, throught the loads in series, and back out the other hot
leg. Nothing flows in the neutral. Again, in my world, that's 200
amps flowing in the service, not 400.
No, never said that.
>
> What if you have a 200A load on the Line 1 to neutral side, and nothing
> loading the Line 2 to neutral side? Are you still going to have 200A going
> thru each "leg" of the main breaker?- Hide quoted text -
>
> - Show quoted text -
You're going to have 200A flowing from Line 1 to neutral. Again,
that is 200 amps flowing in the service cable. As I said, if it's
fully loaded, you will have a max of 200 amps flowing in the service
cable. That's 200 amps coming in, 200 amps going out. The only
difference is whether some of the current flows on the neutral or
not. If the neutral has some current, then one of the hot lines must
have less than 200 amps or you'd violate Kirchoff's law.
Take twenty four .05 ohm resistors. Wire them is series. In series
they equal 1.2 ohms, Connect them across the 240V, 200 amp service
hot lines. You now have 10 volts across each resistor and 200 amps
flowing through the circuit. So, you're supporting twenty four 200
amp, 10volt loads. Each resistor sees 10volts and 200 amps. Taken
together that's 4800A at 10V. How much current is flowing in the
service? Still 200 amps. Showing once again that this feature works
because to get loads of more than 200 amps out of a 200 amp service,
the loads have to appear in series.
>On Oct 27, 8:36=A0pm, usenet-659f31de7f953...@asgard.slcc.edu wrote:
>> The only way you can get 400A out of a 200A service is with a step-down
>> transformer.
>
>I think we are in agreement, except for perhaps one point.
>
>From your previous post, you clearly agree that you can in fact have
>two 120volt, 200 amp loads connected in series across the 240volt
>service. That is a perfectly balanced load. You now have 200 amps
>flowing in series through each load. In my world that is in fact
>"supporting" 400 amps of 120volt load.
Your semantics create confusion. In NO CASE can you flow more than 200 amps
through any single load. To say that you have many 120V loads drawing a
total of 400A is WRONG and obscures the fact that two balanced 120V loads is
absolutely identical to a 240V load.
--
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> And I think all of us are still waiting for a simple answer from Doug
> as to how many amps are actually flowing in a fully loaded 200 amp
> service cable circuit. I've asked that several times now and still
> have no answer, despite having fully answered all his questions.
You've done a terrific job debating this, and you've explained it better
than I could have. I bowed out early on for two reasons: One reason was
that I have limited patience for explaining things to people who
stubbornly defend their own ignorance. The second reason is that I
really am not thoroughly conversant in residential wiring schemes. You
clearly know a lot more about that than I do.
As far as Doug, I'd trust him to install, upgrade, maintain, or repair
any wiring in my house, anytime. I consider him one of the groups
foremost NEC experts, and he clearly knows everything he needs to know
to work with residential wiring at any level.
But, and I mean no disrespect for him, it's very clear to me from this
thread and others, that he doesn't understand electric circuit
fundamentals at all. His grasp of ohm's law, series vs. parallel vs.
series-parallel, etc., is shaky at best. You've brought up our pal
Kirchoff on several occasions, and I'd bet a cup of designer coffee that
Doug has never heard of the fellow.
Now, I don't hold ignorance against a man. What does raise an eyebrow is
when someone who doesn't understand something, declines to acknowledge
that, puffing up his chest and blundering confidently along, refusing to
stand corrected. Damn the torpedoes. At this juncture I'm not insisting
on putting Doug or anyone else in those shoes. Let each man evaluate his
own stance. But I do have my opinions about it.
As for the intent of the OP's question, I've yet to really understand
it, though I'm sure the thread has strayed beyond what he might have
wanted to know. I've learned some things along the way as I've lurked,
which is good.
To get the max of 200A of 240V load you have to have the special case
where the loads add up to 200A. The discussion is about the special
cases of a fully loaded service.
> And
> then you in fact have a SINGLE circuit with 200 amps flowing in on one
> hot leg, throught the loads in series, and back out the other hot
> leg. Nothing flows in the neutral. Again, in my world, that's 200
> amps flowing in the service, not 400.
What did the OP want to know?
IMHO, the OP was asking how many amps of 120V load you can hang on a
200A 240V service. The correct answer is 400.
--
bud--
No, never said that.
But you still didn't answer the question about the current flow path. If you
have a 120V 200A load between Line 1 & neutral,and no load between Line 2 &
neutral, how much current flows thru the Line 1 side of the main breaker,
how much current flows thru the Line 2 side of the main breaker, and how
much thru the neutral?