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





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

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

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

Here's another example. * Take a cardboard box that will be our
"house". * *Take an extension cord, put a 120Watt bulb on the end of
it, plug it in to a 120V outlet and put the bulb in the box. * *You
now have a 120volt, 1amp service to the box. * 1 amp is flowing in the
circuit.
Now replace the bulb with two 60Watt bulbs in series. * Across each
bulb you will have 60 volts and 1 amp will be flowing in each of
them. * So, you are supporting two 1 amp loads at 60volts, * *But what
is flowing in that extension cord? * *It's still 1 amp, not 2.. *

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

That isn't what you intended.

Yes, I agree. *good catch.

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

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

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

*....

Let me restate what I've said all along:

The arguments have gotten so twisted let me start here.

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

Here's a simple series of questions:

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

How much current is flowing in

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

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

How much current is flowing in:

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

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

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

How much current is flowing in:

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

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

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

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

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

Its gotta be a point-of-view problem.

--

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

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

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

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

bud--- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show 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- Hide quoted text -

- Show quoted text -

in other words, is this:

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

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

Mark