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Posted by Doug Miller on October 26, 2009, 10:37 pm
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>>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.
show/hide quoted text
>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.
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Posted by JIMMIE on October 27, 2009, 12:00 am
On Oct 26, 10:37=A0pm, spamb...@milmac.com (Doug Miller) wrote:
show/hide quoted text
all.invalid> wrote:
> >>If all the loads supplied by that service are 120V loads (e.g. blender,
> >>toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do y=
ou get
show/hide quoted text
> >>when you divide that maximum power by 120V?
> >That would be 400A.
> Exactly so.
> >Of course that's only in your imagination since
> >the math is invalid (120V is obtained by splitting the service into 2
> >separate halves, each of which is only 24KW).
> 200A each. Total of 400A of 120V loads -- as you said.
Where in the box can you measure 400 amps? If the panel is controlling
48KW there will be no current on the neutral because the currents will
be balanced. The current that flows through one half of the breaker is
the same current that flows through the other half of the breaker. In
this case what you have is two 200 amp breakers in series. Doug you
have more current coming into the box than going out and that shouldnt
happen.
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Posted by Steve N. on October 27, 2009, 1:35 am
On Oct 26, 10:37 pm, spamb...@milmac.com (Doug Miller) wrote:
show/hide quoted text
> >>If all the loads supplied by that service are 120V loads (e.g. blender,
> >>toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do
> >>you get
> >>when you divide that maximum power by 120V?
> >That would be 400A.
> Exactly so.
> >Of course that's only in your imagination since
> >the math is invalid (120V is obtained by splitting the service into 2
> >separate halves, each of which is only 24KW).
> 200A each. Total of 400A of 120V loads -- as you said.
>Where in the box can you measure 400 amps? If the panel is controlling
>48KW there will be no current on the neutral because the currents will
>be balanced. The current that flows through one half of the breaker is
>the same current that flows through the other half of the breaker. In
>this case what you have is two 200 amp breakers in series. Doug you
>have more current coming into the box than going out and that shouldnt
>happen.
The power is coming in from a transformer secondary winding that is
center-tapped. Let's call the 3 wires
Line 1, the neutral & Line 2 (seee the link below that shows a transformer
secondary at the bottom of the page). When you put 120V loads across Line 1
& neutral, they are independent of Line 2. In effect, you're only using half
of the transformer secondary, so you're only going thru the Line 1 half of
the main breaker. The current path is from the Line 1 side of the secondary
winding, thru the Line 1 side of the main breaker, thru the load, and back
thru the neutral to the Line 1 half of the secondary winding. If you also
put a 120V load across Line 2 and the neutral, then the current path is from
the Line 2 side of the secondary winding thru the Line 2 side of the main
breaker, thru the load, and back thru the neutral (in the opposite direction
of current flow of the Line 1 current thru the neutral) and back to the Line
2 side of the secondary winding. Both loads form their own circular loops
that are independent of each other, except for sharing the neutral (in
opposite directions) to complete their separate circuits. Here is a great
explanation of the transformer secondary, using the battery analogy which
the author (not me) originally designed to show balanced loads, but is also
useful in showing how 120V loads form independent circuits on each side of
the secondary. You can even close the various switchs and see the effect.
http://home.comcast.net/~ronaldrc/wsb/ax.htm
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Posted by Steve N. on October 27, 2009, 2:37 am
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> On Oct 26, 10:37 pm, spamb...@milmac.com (Doug Miller) wrote:
>> >>If all the loads supplied by that service are 120V loads (e.g. blender,
>> >>toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do
>> >>you get
>> >>when you divide that maximum power by 120V?
>> >That would be 400A.
>> Exactly so.
>> >Of course that's only in your imagination since
>> >the math is invalid (120V is obtained by splitting the service into 2
>> >separate halves, each of which is only 24KW).
>> 200A each. Total of 400A of 120V loads -- as you said.
>>Where in the box can you measure 400 amps? If the panel is controlling
>>48KW there will be no current on the neutral because the currents will
>>be balanced. The current that flows through one half of the breaker is
>>the same current that flows through the other half of the breaker. In
>>this case what you have is two 200 amp breakers in series. Doug you
>>have more current coming into the box than going out and that shouldnt
>>happen.
> The power is coming in from a transformer secondary winding that is
> center-tapped. Let's call the 3 wires
> Line 1, the neutral & Line 2 (seee the link below that shows a transformer
> secondary at the bottom of the page). When you put 120V loads across Line
> 1 & neutral, they are independent of Line 2. In effect, you're only using
> half of the transformer secondary, so you're only going thru the Line 1
> half of the main breaker. The current path is from the Line 1 side of the
> secondary winding, thru the Line 1 side of the main breaker, thru the
> load, and back thru the neutral to the Line 1 half of the secondary
> winding. If you also put a 120V load across Line 2 and the neutral, then
> the current path is from the Line 2 side of the secondary winding thru the
> Line 2 side of the main breaker, thru the load, and back thru the neutral
> (in the opposite direction of current flow of the Line 1 current thru the
> neutral) and back to the Line 2 side of the secondary winding. Both loads
> form their own circular loops that are independent of each other, except
> for sharing the neutral (in opposite directions) to complete their
> separate circuits. Here is a great explanation of the transformer
> secondary, using the battery analogy which the author (not me) originally
> designed to show balanced loads, but is also useful in showing how 120V
> loads form independent circuits on each side of the secondary. You can
> even close the various switchs and see the effect.
> http://home.comcast.net/~ronaldrc/wsb/ax.htm
I need to make a correction - the Line 2 current flow would be down the
neutral, thru the load, up thru the Line 2 half of the breaker, back to the
Line 2 side of the transformer. The currents flow in the same direction thru
the transformer secondary "halves", and in opposite directions thru the
neutral.
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Posted by trader4 on October 27, 2009, 11:45 am
show/hide quoted text
> > On Oct 26, 10:37 pm, spamb...@milmac.com (Doug Miller) wrote:
> >> >>If all the loads supplied by that service are 120V loads (e.g. blend=
er,
show/hide quoted text
> >> >>toaster, light bulbs, range hood, stereo, TV, computer, etc.) what d=
> >> >>you get
> >> >>when you divide that maximum power by 120V?
> >> >That would be 400A.
> >> Exactly so.
> >> >Of course that's only in your imagination since
> >> >the math is invalid (120V is obtained by splitting the service into 2
> >> >separate halves, each of which is only 24KW).
> >> 200A each. Total of 400A of 120V loads -- as you said.
> >>Where in the box can you measure 400 amps? If the panel is controlling
> >>48KW there will be no current on the neutral because the currents will
> >>be balanced. The current that flows through one half of the breaker is
> >>the same current that flows through the other half of the breaker. In
> >>this case what you have is two 200 amp breakers in series. Doug you
> >>have more current coming into the box than going out and that shouldnt
> >>happen.
> > The power is coming in from a transformer secondary winding that is
> > center-tapped. Let's call the 3 wires
> > Line 1, the neutral & Line 2 (seee the link below that shows a transfor=
mer
show/hide quoted text
> > secondary at the bottom of the page). When you put 120V loads across Li=
> > 1 & neutral, they are independent of Line 2. In effect, you're only usi=
> > 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 t=
> > secondary winding, thru the Line 1 side of the main breaker, thru the
> > load, and back thru the neutral to the Line 1 half of the secondary
> > winding.
Agree.
If you also put a 120V load across Line 2 and the neutral, then
show/hide quoted text
> > the current path is from the Line 2 side of the secondary winding thru =
the
show/hide quoted text
> > Line 2 side of the main breaker, thru the load, and back thru the neutr=
> > (in the opposite direction of current flow of the Line 1 current thru t=
> > neutral) and back to the Line 2 side of the secondary winding. Both loa=
> > form their own circular loops that are independent of each other, excep=
> > 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?
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>>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.