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wire size and 200amp service tommears 06-27-2007
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Posted by on June 28, 2007, 4:26 pm
wrote:

>Are the only personal preference possibilities based on the
>misunderstanding that aluminum in large gauges is not good,

Probably. There is really no problem with aluminum in aluminum rated
lugs. Some tests actually have shown that an aluminum conductor
performs better than copper in an aluminum lug. Most large lugs are
aluminum.

Special 468x60
Posted by Pete C. on June 28, 2007, 7:01 pm
mm wrote:
>
> wrote:
>
> >Tim Smith wrote:
> >>
> >> gfretwell@aol.com wrote:
> >> > On Wed, 27 Jun 2007 17:34:42 -0700, tommears@comcast.net wrote:
> >> >
> >> > > I work for a major residential electrical
> >> > >equipment maker (starts with a "S" and ends with "iemens")...and our
> >> > >construction sales people tell me that the latest version of NEC
> >> > >requires 4/0 aluminum wiring for 200amp service.
> >> >
> >> > They are right
> >>
> >> Does it require aluminum? If his current aluminum wiring doesn't meet
> >> the current code and will have to be replaced, should he be considering
> >> switching from aluminum at the same time?
> >>
> >> --
> >> --Tim Smith
> >
> >That's certainly an option, but not essential. Aluminum wiring is not an
> >issue for these large gauges, it was only an issue when used in the
> >small gauge (14-10) general wiring in houses. It's mostly a cost and
> >personal preference issue as for service entrance use either is
>
> I don't understand "personal preference". It looks good with my eyes?
> I have stock in a copper company?

Aluminum conductors are more flexible than the equivalent copper
conductors and therefore easier to handle, especially for long pulls.
Copper conductors don't need to have anti-ox compound applied to the
connections. Current prices of each material come into play. The
physically smaller space occupied by the copper cable of a given current
rating can be a factor. Bottom line, personal preference as to which
issue are most important to you.

>
> Are the only personal preference possibilities based on the
> misunderstanding that aluminum in large gauges is not good,

AL wiring in small gauges and terminated at devices without the proper
ratings is not good.

Posted by mm on June 29, 2007, 1:40 am
wrote:

>
>> I don't understand "personal preference". It looks good with my eyes?
>> I have stock in a copper company?
>
>Aluminum conductors are more flexible than the equivalent copper
>conductors and therefore easier to handle, especially for long pulls.
>Copper conductors don't need to have anti-ox compound applied to the
>connections. Current prices of each material come into play. The
>physically smaller space occupied by the copper cable of a given current
>rating can be a factor. Bottom line, personal preference as to which
>issue are most important to you.

OK, I get it. Thanks a bunch.
>>
>> Are the only personal preference possibilities based on the
>> misunderstanding that aluminum in large gauges is not good,
>
>AL wiring in small gauges and terminated at devices without the proper
>ratings is not good.


Posted by William Underhill on June 27, 2007, 9:21 pm
tommears@comcast.net wrote:
> I am doing a significant kitchen upgrade and the contractor has
> recommended that I upgrade the electrical service to 200amp. I've had
> 3 electricians out to quote on the work---and received 3 very
> different opinions and prices. Two have told me it is not necessary
> to upgrade the main power line in the house from the meter to the load
> center. The other one says I must.
>
> I currently have 150amp service. The meter and the load center are
> separated by about 50-feet. The wiring from the meter to the load
> center is 2/0 aluminum. I work for a major residential electrical
> equipment maker (starts with a "S" and ends with "iemens")...and our
> construction sales people tell me that the latest version of NEC
> requires 4/0 aluminum wiring for 200amp service.
>
> What is up with 2 of these contractors telling me it is OK to upgrade
> without replacing the existing 2/0 wiring?
>
> Is there some sort of grandfather provision in this situation?
>
> If the price difference wasn't so much it would be a no-brainer. But
> at $3,500 vs. $750 it's a lot harder to go with the cadillac solution
> simple because it is the cadillac solution....
>
> Does anyone have any guidance on the issues and realities of this
> situation?

Hmm. Disclaimer first - I'm a naval electrical technician, not civilian,
so am not intimately familiar with civilian code requirements. Further,
I'm Canadian, and if you're not, some of your code requirements may vary.

That said, check out this website:
http://www.friesen.com/manuals/allowable_ampacities.asp#Single%20Aluminum%20Conductors%20in%20Free%20Air

Depending on your insulation type and ambient temp, you'd need at least
3/0 to meet the requirements, and 4/0 gives you only a 30-amp safety
margin. As I said, I'm not familiar with the details of the NEC, but in
the Navy we'd be using the 4/0, since we have to assume that all loads
are energized at all times. There may indeed be some kind of
'grandfathering' provision, but I'd rather not create an electrical fire
risk.

Yours aye,
W. Underhill

--
"Take sides! Always take sides! You may sometimes be wrong - but the man
who refuses to take sides must *always* be wrong! Heaven save us from
poltroons who fear to make a choice!" R.A. Heinlein, "Double Star"

Posted by Bud-- on June 28, 2007, 11:19 am
William Underhill wrote:

>
> Hmm. Disclaimer first - I'm a naval electrical technician, not civilian,
> so am not intimately familiar with civilian code requirements. Further,
> I'm Canadian, and if you're not, some of your code requirements may vary.
>
> That said, check out this website:
>
http://www.friesen.com/manuals/allowable_ampacities.asp#Single%20Aluminum%20Conductors%20in%20Free%20Air
>

You actually want table 4 (in conduit/cable) which has even lower amp
ratings.

>
> Depending on your insulation type and ambient temp, you'd need at least
> 3/0 to meet the requirements, and 4/0 gives you only a 30-amp safety
> margin. As I said, I'm not familiar with the details of the NEC, but in
> the Navy we'd be using the 4/0, since we have to assume that all loads
> are energized at all times. There may indeed be some kind of
> 'grandfathering' provision, but I'd rather not create an electrical fire
> risk.
>

The US-NEC allows 4/0 Al for 200A residential services. In a residence
all loads are not energized at all times. The major loads, in
particular, cycle on and off. I believe the wire sizes were based on
field studies.

4/0 can not be used for 200A non-residential services where major loads
may be energized all the time.

--
bud--

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