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.
I'm not so sure, as I have yet to hear Doug acknowledge that there is
actually only a 200 amp current flowing in that service cable. When
asked that by others he has replied with answers that try to link it
to voltage, ie 200 amps at 240V or 400 amps at 120V. And that is
simply wrong. Amps and voltage are two different things. There is
never more than 200 amps flowing in that service cable circuit.
On Oct 27, 8:36 pm, firstname.lastname@example.org wrote:
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.
On Wed, 28 Oct 2009 02:24:20 -0700 (PDT), in alt.home.repair,
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.
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
On Oct 26, 7:18 pm, email@example.com (Doug Miller) wrote:
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
You can divide and get any answer you want. I could divide 48KVA by
10volts and get 4800 amps. So a 200 amp service could support a
total 4800 amp, 10 volt load too. But how much max current is
actually flowing in the service cable entering the house? Exactly
the same as always, 200 amps. If you believe otherwise, please tell
us what currents are flowing in each of the three conductors.
On Oct 27, 2:04 pm, firstname.lastname@example.org (Doug Miller) wrote:
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.
(Doug Miller) wrote:>Also, you only get those 400 amps if the load is balanced so that it
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
>The 200 amp current flows in one hot and
No, the main breaker would open long before any melting
A whole bunch for a few microseconds. A breaker isn't instantaneous.
Yes, I agree, assuming there is one. In our hypothetical case I was
ignoring any breakers.
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.
Yes, I agree, assuming there is one. In our hypothetical case I was
ignoring any breakers.
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??
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 Sat, 24 Oct 2009 23:55:15 GMT, email@example.com (Doug Miller)
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.
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?
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
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
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
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