0 copper wire

Discussion in 'Misc Electronics' started by cm, May 3, 2004.

1. cmGuest

Could someone tell how much amperage you would get using 700' of 0
copper wire from a 240V 200 amp service?
Thanks,
curt

3. hungry1Guest

Do you mean that until I apply a load , there's no way to determine how

4. John FieldsGuest

---
No, what I mean is that unless you know what the load looks like, (and
all the rest of it) it's going to be impossible to determine what the
temperature rise in the cable is going to be and since the temperature
rise will cause the resistance of the wire to rise, the amount of
voltage it'll drop will increase, causing the voltage across the load
to decreaase by the amount dropped in the wire.

For example, if you've got 700' of wire, (350' out and 350' back, say)
since #0 AWG soft-drawn copper wire has a resistance of about 0.1 ohms
per 1000 feet, that'll be a resistance of 0.07 ohms.

Now, if what you've got on the end of the cable wants to see
240V ±10%, then the most the cable can drop is 24V, and since I = E/R,
the most current you can put through it will be 240V/0.07R ~ 3429
amps.

BUT... with 3429 amps flowing through the cable it'll be dissipating
P = I*E = 3429A * 24V = 82,296 watts, so that's about 118 watts per
foot. That cable's going to get HOT, and when it does its resistance
is going to increase, which will further reduce the voltage across,
and the current through, the load.

So, in order to be able to figure out what the wire's going to do, you
need to know what the load looks like so you can pick an appropriate
wire size. Also, you need to know where the cable's going to be and
what it's covered with so you can determine how well it'll be able to
get rid of the heat it's going to generate when current passes through
it.

5. Bob MyersGuest

Of course not, but that's not what was asked. Looking
back at the original question:

"How much amperage you would get" appears to be a question
asking how much current would actually be drawn, and this is
impossible to say, as John noted. Assuming that "0 copper wire"
refers to a copper wire of the 0 AWG size (and not a wire that
contains "zero copper"!), the wire will very likely be capable of
carrying the full 200 A that the service is capable of providing
(actually, types T or TW at 0 AWG are only rated to 195A at
normal ambients, but let's call it close enough for the moment), but
who knows at this point how much will actually be drawn by

If this IS a question about capacity, then 00 AWG or might be
a better choice.

Bob M.

6. Tony NewmanGuest

Perhaps a nitpick, but I think you shifted from a 24 volt drop to
dropping the entire 240 volts across the wire resistance. The amperage
would come out to about 343 amps to get a 24 volt drop. Still, losing
about 8200 watts in wire resistance is not something to ignore.

want to put on a 200 amp circuit, the loss would be (E=I*R) 180 * .07 =
12.6 volts. This would have the wire dissapating 2268 watts over 700
feet or about 3.25 watts per foot. The wire would get warm, but should
stay tolerable. There would also be a 6.3 volt difference between the
neutral and "real" ground at the load, which might cause another set of
problems.

For the original poster... The maximum amperage you could get after
going through 700 feet of 0 AWG wire comming from a 200 amp service, is
200 amps. Any more would trip the circuit breaker (if pushed to the
full 200 amps, you would get occasional trips anyway). And remember,
as John pointed out, you have to figure the full round-trip travel the
electricity takes. If you are really 700 feet from the service panel,
you are running through 1400 feet of wire. Maybe the real question is
how much voltage loss can your load stand, and how much do you want to
pay to heat the wires. Going to a heavier wire size is a one-time
expense. Losing energy in the wires costs you every time you pay your
electricity bill.

7. hungry1Guest

Maybe I need to give more details and revise my question.
What size wire would one need to run service to 10 homes in a distance of
700'???
Thanks,
curt

9. Bob MyersGuest

That's a completely different question! And I have to assume that
when you speak of "200 A service" in this case, you mean that
EACH HOME has a 200 A service, right? Splitting 200 A among
10 homes would be silly...

Given that, what you're REALLY asking is what you need to handle
a total of 2000A max. split among 10 homes - but now the topology
of the system becomes important. Are these 10 homes all strung
out in a line (which means that the connection from the "main" supply
to the first home has to be able to carry the full 2000 A, the next
one 1800A, and so forth) or are they in a "star" configuration from one
central point, or what? And do you really intend to run all ten off the
same point, or will they be fed from a higher voltage (lower current)
line and then have transformers, either for each individual connection
or shared among some smaller groups within the 10-home total?

The real point here is that - if you have to ask this question, I think that
project. Either that, or you're asking us to do your homework for you.

Bob M.

10. hungry1Guest

Sorry if I offended anyone, with my questions, I am trying to help people
get electric to their homes in my area with a generator that outputs
200amps.We can get single 0 copper wire where we are. but the information
that I need is NOT available to my knowledge. We are in a remote area of a
different country from the USA.
I just thought this was the place that I might get some info to help me. I
will not bother you guys to "do my homework for me anymore".
Thanks,
curt

11. Bob MyersGuest

OK, with THAT information provided -

0 AWG copper wire is rated to at least 195 A for about any type
in common use, so it has sufficient capacity. You wouldn't
want to run all 10 homes "in series" anyway, as there would be
excessive drop in the wire and - well, this just isn't the most
efficient way to do this. The best thing to do would be to
run individual lines from the generator to each home, but that is
rarely practical. Most likely, your best bet would be to place the
generator so that it is as centrally-located as possible,
and then run branches from there to groups of homes or individual
homes as needed - in short, try to spread the total load, and distance,
as evenly as you can among several branches. If you have to have
one or more homes signficantly farther away from the generator than
others, try to minimize the load on that branch - in other words, you
can trade the load in any given branch for the length of that branch,
so that no one sees an excessive drop. Single branches to each
home, if they're all going to be limited to 20A each, could do with
wire a good deal smaller than 0 AWG, even if each branch were
700' long. 2 AWG would be acceptable for a run that long, for
instance, and smaller sizes would be similarly acceptable for
shorter distances (you could drop down to 4 AWG all around
if the generator were centrally located within a 700' overall
circle, such that no load were farther away than 350', and
you'd still see <= a 2% drop). (These figures are for copper
wire only - if you were using aluminum, which has other problems,
you'd need larger wire in all cases. All of this information, by the
way, is pretty widely available on the web.)

Having said that...20A/home (assuming we're talking about 220
or 240 V service, a bit over 2 kW) isn't a whole lot by most
standards, but I would certainly admit that it's better than no
electricity at all. You would want to provide breakers at both the
generator and at the individual homes, of course. And PLEASE note
that even if this is a "different country from the USA" - there ARE
still such things as electrical building and safety codes, and they
exist for a very good reason. Electricity can be very dangerous
stuff, and is not to be played around with. If you don't have access
to such basic information as the current capacity of copper wire,
then I would have to question whether or not you have sufficient
expertise to do what you are proposing properly and safely. It
IS nice to be able to have electric lights and such, but it's far more
important that no one gets killed or has their home burned down
in the process of getting those things. In short, I'd have to
strongly advise against trying to install this sort of system yourself
unless you can get some expert assistance.

Bob M.

12. hungry1Guest

I am on an island that already has some grid electric, and have been
promised to one day have it where I live.
Until then, I can get by with the information you gave me.I really
appreciate it!
Thank again,
curt