What amperage is Romex #8 copper wire? On some charts I see 40 A and
on some I see 50 A.

"ls02" wrote in message
...
What amperage is Romex #8 copper wire? On some charts I see 40 A and
on some I see 50 A.

In a NM cable #8 uses the 60 degree figure, which is 40 amp

On Feb 1, 10:27*am, ls02 wrote:
What amperage is Romex #8 copper wire? On some charts I see 40 A and
on some I see 50 A.

Individual wires you could use 8. There are a number of calculators
out there on the web that will help with wire selection. Distance is
a factor as well. Plus what's at the other end. Motors that start
under a load like a big hvac compressor may need bigger wire simply to
prevent to much voltage drop at urge current.

On Feb 1, 10:59*am, jamesgangnc wrote:
On Feb 1, 10:27*am, ls02 wrote:

What amperage is Romex #8 copper wire? On some charts I see 40 A and
on some I see 50 A.

Individual wires you could use 8. *There are a number of calculators
out there on the web that will help with wire selection. *Distance is
a factor as well. *Plus what's at the other end. *Motors that start
under a load like a big hvac compressor may need bigger wire simply to
prevent to much voltage drop at *urge current.

The wire is used to connect sub-panel to mail panel. The distance is
3'.

On Feb 1, 10:59*am, jamesgangnc wrote:
On Feb 1, 10:27*am, ls02 wrote:

What amperage is Romex #8 copper wire? On some charts I see 40 A and
on some I see 50 A.

Individual wires you could use 8. *There are a number of calculators
out there on the web that will help with wire selection. *Distance is
a factor as well. *Plus what's at the other end. *Motors that start
under a load like a big hvac compressor may need bigger wire simply to
prevent to much voltage drop at *urge current.

In the case of general loads and Romex, it's 8 gauge for 40. With an
HVAC
load, the rules change. The circuit has to be wire sized to at least
the
minimum specd by the manufacturer. The breaker has to be sized
between the min and max specd by the manufacturer. This leads to
installations that are correct and to code, but that would be a
violation
of the rules for general purpose branch circuits.

As an example, if you have an AC unit rated for 35 amp min circuit and
rated for a breaker of 40amp min, 60 max, you could have a 60 amp
breaker using 8 gauge wire. The reasoning to this is that:

A - the AC has a high starting current that doesn't last

B- the AC has it's own built-in over current protection and is the
only
device on that circuit.

"ls02" wrote in message
...
On Feb 1, 10:59 am, jamesgangnc wrote:
On Feb 1, 10:27 am, ls02 wrote:

What amperage is Romex #8 copper wire? On some charts I see 40 A and
on some I see 50 A.

Individual wires you could use 8. There are a number of calculators
out there on the web that will help with wire selection. Distance is
a factor as well. Plus what's at the other end. Motors that start
under a load like a big hvac compressor may need bigger wire simply to
prevent to much voltage drop at urge current.

The wire is used to connect sub-panel to mail panel. The distance is
3'.

Run a 3' length of 1" PVC between the panels and use #8 THHN copper on a 50
amp breaker

So, 8 gage wire is 8 gage? He asked the amp capacity of #8
copper.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"jamesgangnc" wrote in message
...
On Feb 1, 10:27 am, ls02 wrote:
What amperage is Romex #8 copper wire? On some charts I
see 40 A and
on some I see 50 A.

Individual wires you could use 8. There are a number of
calculators
out there on the web that will help with wire selection.
Distance is
a factor as well. Plus what's at the other end. Motors
that start
under a load like a big hvac compressor may need bigger wire
simply to
prevent to much voltage drop at urge current.

wrote in message
...
On Tue, 1 Feb 2011 11:26:16 -0500, "RBM" wrote:


"ls02" wrote in message
...
On Feb 1, 10:59 am, jamesgangnc wrote:
On Feb 1, 10:27 am, ls02 wrote:

What amperage is Romex #8 copper wire? On some charts I see 40 A and
on some I see 50 A.

Individual wires you could use 8. There are a number of calculators
out there on the web that will help with wire selection. Distance is
a factor as well. Plus what's at the other end. Motors that start
under a load like a big hvac compressor may need bigger wire simply to
prevent to much voltage drop at urge current.

The wire is used to connect sub-panel to mail panel. The distance is
3'.

Run a 3' length of 1" PVC between the panels and use #8 THHN copper on a
50
amp breaker


If this is only 3 feet, why cheap out on the wire. Put in #2 and you
can set a 100a sub panel. You may never need it but you have it for
virtually no additional expense.

A moment after I hit the send button, I had that exact thought

On 2/1/2011 11:54 AM, Stormin Mormon wrote:
So, 8 gage wire is 8 gage? He asked the amp capacity of #8
copper.

Actually, you could put 100 amps through an 8 gauge wire ... not for
very long. It's all a matter of heating and insulation and how many
wires are packing into a tight (conduit) space. That's why we have
NEC which specifies the current for different sizes and types of
wires and how they are routed.

On Feb 1, 11:54*am, "Stormin Mormon"
wrote:
So, 8 gage wire is 8 gage? He asked the amp capacity of #8
copper.

--
Christopher A. Young
Learn more about Jesus
*www.lds.org
.

"jamesgangnc" wrote in message

...
On Feb 1, 10:27 am, ls02 wrote:

What amperage is Romex #8 copper wire? On some charts I
see 40 A and
on some I see 50 A.

Individual wires you could use 8. *There are a number of
calculators
out there on the web that will help with wire selection.
Distance is
a factor as well. *Plus what's at the other end. *Motors
that start
under a load like a big hvac compressor may need bigger wire
simply to
prevent to much voltage drop at *urge current.


Umm no, the OP asked the rating of #8 Romex wire...

Some have responded that #8 THHN individual wires
are rated slightly higher...

Are you unable to actually read the entire thread
before adding your own "wisdom"...

~~ Evan

On Feb 1, 10:23*pm, Evan wrote:
On Feb 1, 11:54*am, "Stormin Mormon"





wrote:
So, 8 gage wire is 8 gage? He asked the amp capacity of #8
copper.

--
Christopher A. Young
Learn more about Jesus
*www.lds.org
.

"jamesgangnc" wrote in message

....
On Feb 1, 10:27 am, ls02 wrote:

What amperage is Romex #8 copper wire? On some charts I
see 40 A and
on some I see 50 A.

Individual wires you could use 8. *There are a number of
calculators
out there on the web that will help with wire selection.
Distance is
a factor as well. *Plus what's at the other end. *Motors
that start
under a load like a big hvac compressor may need bigger wire
simply to
prevent to much voltage drop at *urge current.

Umm no, the OP asked the rating of #8 Romex wire...

Some have responded that #8 THHN individual wires
are rated slightly higher...

Are you unable to actually read the entire thread
before adding your own "wisdom"...

~~ Evan- Hide quoted text -

- Show quoted text -

Same response I gave. I just added other factors that might affect
wire choice. Now that we know it's 3 feet to a subpanel there's not
much reason not to use bigger wire since there would be no noticable
cost difference.

RBM wrote:
"ls02" wrote in message
...
On Feb 1, 10:59 am, jamesgangnc wrote:
On Feb 1, 10:27 am, ls02 wrote:

What amperage is Romex #8 copper wire? On some charts I see 40 A and
on some I see 50 A.

Wire have many different kinds of electrical insulation. Some kinds of
insulation can be used at various higher temperatures. That allows a
higher current rating - higher current produces more heat. Romex is
limited to the current for 60 degree insulation, which for #8 is 40A.
(There further details you don't want to know about.)

Individual wires you could use 8. There are a number of calculators
out there on the web that will help with wire selection. Distance is
a factor as well. Plus what's at the other end. Motors that start
under a load like a big hvac compressor may need bigger wire simply to
prevent to much voltage drop at urge current.

The wire is used to connect sub-panel to mail panel. The distance is
3'.

Run a 3' length of 1" PVC between the panels and use #8 THHN copper on a 50
amp breaker


There is a limitation (110.14-C-1) on "ampacity" rating of the wire
based on the terminals the wire is connected to.

for circuits 100A and less, or terminals marked #14 through #1, the 60
degree ampacity of the wire is used.

for circuits over 100A, or terminals marked larger than #1, the 75
degree ampacity of the wire is used (unless the wire is rated 60 degrees)

In both cases wires of a higher temperature rating can be used, but the
current allowed is limited to the 60 or 75 degree column.

In both cases the wire can be used at a higher current if both terminal
devices are marked for a higher temperature.

I expect you know all that, but some may not.


Long time since I looked at a breaker - a new 20A SquareD breaker is
marked for 60 or 75 degree wire, which means the 75 degree column can be
used for 90 degree rated THHN. If a 50A breaker is similarly marked, the
usable rating for #8 THHN is 50 amps, as stated.

Are most new breakers marked for 75 degrees these days?
Is this enforced?

Presumably connections to old breakers that aren't marked would hit the
60/75 degree temp limit.

--
bud--

wrote:
On Wed, 02 Feb 2011 10:57:08 -0600, bud--
wrote:

Long time since I looked at a breaker - a new 20A SquareD breaker is
marked for 60 or 75 degree wire, which means the 75 degree column can be
used for 90 degree rated THHN. If a 50A breaker is similarly marked, the
usable rating for #8 THHN is 50 amps, as stated.

The only problem with that is 240.4(D) will limit you to 12ga or
larger wire on a 20a breaker so you can't even use the 60c column in
310.16

The only recent breaker I have available is the 20A SquareD. Shouldn't
have commented on 75 degree for that one. (They even foot note the 310
tables for up to #10.) The question is whether a 50A breaker is rated
for 75 degree wire. If a 20 is I expect a 50A SquareD is.

More generally are breakers 40-100A often rated for 75 degree (or maybe
even 90 degree) wire?

Are breakers over 100A rated for 90 degree wire?

Anything general that can be said about lugs and other terminals?

Kind of annoying to use THHN and not be able to use the 90 degree
ampacity (other than derating).

Do you tag for wire (larger than #10) used at an ampacity over the
terminal rating? (Does anyone take the time to figure out the ratings?)

--
bud--