I added 14-gauge (15A) romex cable to a circuit that had 12-gauge (20A)
wire, indicating I had made a mistake, but it turns out to be a 15A breaker
on the circuit with 12-gauge wire. Is that OK/safe? I don't have to correct
my mistake, right? Thanks

Em wrote:
I added 14-gauge (15A) romex cable to a circuit that had 12-gauge (20A)
wire, indicating I had made a mistake, but it turns out to be a 15A breaker
on the circuit with 12-gauge wire. Is that OK/safe? I don't have to correct
my mistake, right? Thanks

Correct. However, if the #12 wire goes to the panel you may end up
confusing the next person looking at the electrical system--they may
assume that since it's #12 wire its safe to put a 20A breaker on the
circuit, not realizing that the circuit includes some #14..

Chris

Em wrote:
I added 14-gauge (15A) romex cable to a circuit that had 12-gauge
(20A) wire, indicating I had made a mistake, but it turns out to be a
15A breaker on the circuit with 12-gauge wire. Is that OK/safe? I
don't have to correct my mistake, right? Thanks

You already have answers to the same message you posted about 15 minutes
before this one.

--
Joseph Meehan

Dia 's Muire duit

On Mon, 26 Mar 2007 11:01:56 -0600, Chris Friesen
wrote:

Em wrote:
I added 14-gauge (15A) romex cable to a circuit that had 12-gauge (20A)
wire, indicating I had made a mistake, but it turns out to be a 15A breaker
on the circuit with 12-gauge wire. Is that OK/safe? I don't have to correct
my mistake, right? Thanks

Correct. However, if the #12 wire goes to the panel you may end up
confusing the next person looking at the electrical system--they may
assume that since it's #12 wire its safe to put a 20A breaker on the
circuit, not realizing that the circuit includes some #14..

Chris


Some AHJ would have you lable the circuit 15amp only.

tom @ www.Consolidated-Loans.info

In article , Just Joshin wrote:
On Mon, 26 Mar 2007 11:01:56 -0600, Chris Friesen
wrote:

Em wrote:
I added 14-gauge (15A) romex cable to a circuit that had 12-gauge (20A)
wire, indicating I had made a mistake, but it turns out to be a 15A breaker
on the circuit with 12-gauge wire. Is that OK/safe? I don't have to correct
my mistake, right? Thanks

Correct. However, if the #12 wire goes to the panel you may end up
confusing the next person looking at the electrical system--they may
assume that since it's #12 wire its safe to put a 20A breaker on the
circuit, not realizing that the circuit includes some #14..

Chris

Some AHJ would have you lable the circuit 15amp only.

I have before seen a municipality's code webpage saying that it is
against code to have a branch circuit having wires differing in allowed
breaker amps. However, I did not find it clear whether that was NEC or a
local building code.

If you have mixed size wiring in a branch circuit, I would equalize it
if possible. If not, I would have visible tags everywhere the larger
wiring would be seen saying that the branch circuit is a mixed wire size
circuit and what the breaker amps should be - and hope the home inspector
does not see that being a problem when you sell the house.

Personally, I think there should be no permanently installed wiring
thinner than 12 in a house, as common as 20 amp breakers and fuses are.

- Don Klipstein )

On Sun, 1 Apr 2007 05:41:27 +0000 (UTC), (Don
Klipstein) wrote:

In article , Just Joshin wrote:
On Mon, 26 Mar 2007 11:01:56 -0600, Chris Friesen
wrote:

Em wrote:
I added 14-gauge (15A) romex cable to a circuit that had 12-gauge (20A)
wire, indicating I had made a mistake, but it turns out to be a 15A breaker
on the circuit with 12-gauge wire. Is that OK/safe? I don't have to correct
my mistake, right? Thanks

Correct. However, if the #12 wire goes to the panel you may end up
confusing the next person looking at the electrical system--they may
assume that since it's #12 wire its safe to put a 20A breaker on the
circuit, not realizing that the circuit includes some #14..

Chris

Some AHJ would have you lable the circuit 15amp only.

tom @ www.Consolidated-Loans.info

I have before seen a municipality's code webpage saying that it is
against code to have a branch circuit having wires differing in allowed
breaker amps. However, I did not find it clear whether that was NEC or a
local building code.

If you have mixed size wiring in a branch circuit, I would equalize it
if possible. If not, I would have visible tags everywhere the larger
wiring would be seen saying that the branch circuit is a mixed wire size
circuit and what the breaker amps should be - and hope the home inspector
does not see that being a problem when you sell the house.

Personally, I think there should be no permanently installed wiring
thinner than 12 in a house, as common as 20 amp breakers and fuses are.

- Don Klipstein )

Sounds like you have stock in copper mines. In truth 14# is 'safe' at
25 amps with today's romex (for pundents, look at 2005 NEC table
310.16 THHN. However, NM-B (be meaning 90C insulation) must be
treated as 60C insulation. This lowers the amperage rating down to
now 20 amps. Then when you look up 240.4D, you have further derate
14# down to 15 amps.

So what is good/safe 25 amps to 15amps is a fat margin for safety. So
12# in homes is kinda overkill, and not required per the NEC.

Disclaimer: DIY'ers this is a discussion, not a how-to, read the
electrical codes yourself.

tom

On Sun, 1 Apr 2007 05:41:27 +0000 (UTC), (Don
Klipstein) wrote:

In article , Just Joshin wrote:
On Mon, 26 Mar 2007 11:01:56 -0600, Chris Friesen
wrote:

Em wrote:
I added 14-gauge (15A) romex cable to a circuit that had 12-gauge (20A)
wire, indicating I had made a mistake, but it turns out to be a 15A breaker
on the circuit with 12-gauge wire. Is that OK/safe? I don't have to correct
my mistake, right? Thanks

Correct. However, if the #12 wire goes to the panel you may end up
confusing the next person looking at the electrical system--they may
assume that since it's #12 wire its safe to put a 20A breaker on the
circuit, not realizing that the circuit includes some #14..

Chris

Some AHJ would have you lable the circuit 15amp only.

I have before seen a municipality's code webpage saying that it is
against code to have a branch circuit having wires differing in allowed
breaker amps. However, I did not find it clear whether that was NEC or a
local building code.

I'm fairly sure that NEC only requires you to size the breaker for
the smallest wire in the sequence. I'll admit I can see the point
in wanting them all to be the same, though, because it would be
easy for someone to look at the wire leaving the service panel,
notice that it's 12 AWG, and up the breaker to 20A.



If you have mixed size wiring in a branch circuit, I would equalize it
if possible. If not, I would have visible tags everywhere the larger
wiring would be seen saying that the branch circuit is a mixed wire size
circuit and what the breaker amps should be - and hope the home inspector
does not see that being a problem when you sell the house.

Personally, I think there should be no permanently installed wiring
thinner than 12 in a house, as common as 20 amp breakers and fuses are.

On Apr 1, 6:36 pm, Just Joshin wrote:

Long post.

Short version: KISS principle. #14 = 15 amp breaker, #12 = 20 amp
breaker.

Sounds like you have stock in copper mines.

Sounds like you need to take heed in NEC(2005) Section 90.1(C)
Intention:
"This Code is not intended as a design specification or an instruction
manual for untrained persons."

In truth 14# is 'safe' at 25 amps with today's romex

#14 is _NOT_ 'safe' at 25 amps with today's Romex, or any other wire
for that matter, _unless_ the terminals for the electric equipment are
rated for 90 degrees Centigrade AND the conductors do not need to be
derated for temperature! That's 194 degrees F. You will _not_ find
Residential circuit breakers rated for 90 degrees C. Any wire ran in
an attic must be derated for temperature.

(for pundents, look at 2005 NEC table
310.16 THHN.

Yeah, let's do that. The ampacities listed in Table 310.16 are for an
ambient temperature of 30 degrees C, that's 86 degrees F. Try looking
at the TOP of the column where you got that 25 amps. What's that? 90
degrees C? Like I said, good luck finding Residential circuit
breakers and devices with terminals rated at 90 degrees C. For
"pundits" see NEC Section 110.14(C)(1) and (2), which basically state
that conductors cannot be used at the higher temperature rating unless
ALL of the equipment and terminations are is listed and identified, as
in "UL", for such use.

The only practical use for the 90 degree C column in Table 310.16 is
for derating conductors due to temperature and other factors.

However, NM-B (be meaning 90C insulation) must be
treated as 60C insulation. This lowers the amperage rating down to
now 20 amps.

At best one can find Residential circuit breakers rated at 75 degrees
C. Many older circuit breakers are only rated at 60 degrees C. IF
you look at the 75 and 60 degree C columns in Table 310.16, #14 is
rated at 20 amps. If ya try to crank a fully loaded 90 degree
conductor at full 90 degree C rating on a 60 or 75 degree C terminal,
something _is_ eventually going to burn.


Then when you look up 240.4D, you have further derate
14# down to 15 amps.

Yeah, and IF you bother to look at the BOTTOM of Table 310.16, you'll
see (temperature) correction factors. Is it safe to say that a
typical attic can reach 105 degrees F or higher? The correction
factor in the 90 degree column for 105 degrees F is 0.87. Is _not_
Romex commonly installed in attics? Your 25 amps just went from 25
amps to 25 amps x 0.87 = 21.75 amps.

If you bother to look at NEC Section 310.15(B)(2) you'll also see that
adjustment factors must be made for number of conductors in conduit or
bundled, etc. These adjustment factors are even more drastic than for
the temperature correction factors in Table 310.16. The smallest
factor (for 4 to 6 wires) is 80%. 25 amps x 80% = 20 amps. Put 'em
in an attic and that 20 amps just became 20 x 0.87 = 17.4 amps.


So what is good/safe 25 amps to 15amps is a fat margin for safety.

As shown above, that "fat" margin disappears in a hurry. I call it
idiot proofing...see NEC Section 90.1(C).

So 12# in homes is kinda overkill,

Some areas will not allow wire smaller than #12 in houses. See idiot
proofing.

No, it's NOT overkill. Not only that, but a lot of the older Romex
and circuit breakers were only rated at 60 degrees C. Some of it was
75 degree C. When derating for temperature, one then has to derate
from the 60 or 75 degree columns. 20 amps x 0.87 = 17.4 amps, let's
hope it doesn't need further adjustment factors. That's probably why
Romex started getting manufactured circa late 80's with 90 degree C
wire. IMHO, there is no "fat" margin once considerations for
temperature are made. Romex is finally where it should be.....idiot
proof.

When houses are "re-wired", sometimes some of that old wiring is
reused by some electrical contractors. All the more reason, should
one sign a contract to get a house re-wired, to make sure it has a
clause that says something like: "All wiring to be new. Remove or
abandon in place ALL old wiring."

and not required per the NEC.

Yes, #12 is required by NEC for circuits for kitchens, dining rooms,
bathrooms, etc.

Disclaimer: DIY'ers this is a discussion, not a how-to, read the
electrical codes yourself.

I don't need a disclaimer. My comments can be verified by qualified
people anywhere on the Internet, or by your local electrical
inspector. Here's a site that is administered by an electrical
inspector:
http://www.selfhelpandmore.com/index.htm

For online viewing of the NEC:
http://www.nfpa.org/itemDetail.asp?c...kie% 5Ftest=1