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Home > Archive > Electrical Engineering > March 2007 > Wire size vs. Breaker Size---Followup Question
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Wire size vs. Breaker Size---Followup Question
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| Randell Tarin 2007-03-06, 8:25 pm |
| This application is for a bedroom. I should also ask if I can use 15 AMP
rated recepticles with 12 AWG cable on a 15 AMP arc-fault breaker.
| |
| Paul Hovnanian P.E. 2007-03-07, 3:25 am |
| Randell Tarin wrote:
>
> This application is for a bedroom. I should also ask if I can use 15 AMP
> rated recepticles with 12 AWG cable on a 15 AMP arc-fault breaker.
Yes. You can also use 15A receptacles on a general purpose branch
circuit together with 12AWG and a 20 A breaker.
--
Paul Hovnanian mailto:Paul@Hovnanian.com
------------------------------------------------------------------
Do not interfere in the affairs of dragons,
For you are crunchy and tasty with barbecue sauce.
| |
| Long Ranger 2007-03-07, 3:25 am |
|
"Randell Tarin" <thetarins@earthlink.net> wrote in message
news:WuoHh.124653$_73.45013@newsread2.news.pas.earthlink.net...
> This application is for a bedroom. I should also ask if I can use 15 AMP
> rated recepticles with 12 AWG cable on a 15 AMP arc-fault breaker.
#12 copper is rated for 20 amps. You are allowed to go down in amperage for
a given wire size, so running #12 for a 15 amp circuit is perfectly fine,
except for the fact that you are wasting your money doing so. Barring any
extreme situations fo voltage drop, you should be fine using that as a 20
amp conductor as long as you don't mix in any # 14 in the circuit. Using 15
amp receptacles on a 20 amp circuit is O.K. too. Be sure that you "pigtail"
your wire make-up, since a 20 amp circuit is generally not allowed to be
"fed through" a 15 amp outlet, (except GFI's, and those that separately
clamp two conductors under a torqued screw and plate).
| |
| Randell Tarin 2007-03-07, 9:25 am |
| Long Ranger wrote:
> #12 copper is rated for 20 amps. You are allowed to go down in amperage for
> a given wire size, so running #12 for a 15 amp circuit is perfectly fine,
> except for the fact that you are wasting your money doing so.
Had the wire from a previous project. Wanted to use it and not have to
run out and buy 14AWG, which would have indeed been a waste of money.
| |
|
| Long Ranger wrote:
> "Randell Tarin" <thetarins@earthlink.net> wrote in message
> news:WuoHh.124653$_73.45013@newsread2.news.pas.earthlink.net...
>
>
If you are using #12 there is no reason not to use a 20A breaker (unless
you already bought the 15A ones.) The only limit on 15A receptacles on a
20A circuit is you can't have only a single receptacle connected. A
duplex outlet is 2 receptacles.
>
> #12 copper is rated for 20 amps. You are allowed to go down in amperage for
> a given wire size, so running #12 for a 15 amp circuit is perfectly fine,
> except for the fact that you are wasting your money doing so. Barring any
> extreme situations fo voltage drop, you should be fine using that as a 20
> amp conductor as long as you don't mix in any # 14 in the circuit. Using 15
> amp receptacles on a 20 amp circuit is O.K. too. Be sure that you "pigtail"
> your wire make-up, since a 20 amp circuit is generally not allowed to be
> "fed through" a 15 amp outlet, (except GFI's, and those that separately
> clamp two conductors under a torqued screw and plate).
>
15A receptacles are rated 20A feedthrough and 20A total combined load
from both outlets on a duplex receptacle. Since they are allowed on 20A
circuits, they will be connected and used that way. The UL standard
recognizes the likely usage.
--
bud--
| |
| Long Ranger 2007-03-07, 8:25 pm |
|
"Bud--" <remove.BudNews@isp.com> wrote in message
news:25ea4$45eedfa9$4213eb9d$16342@DIALUPUSA.NET...
> Long Ranger wrote:
>
> If you are using #12 there is no reason not to use a 20A breaker (unless
> you already bought the 15A ones.) The only limit on 15A receptacles on a
> 20A circuit is you can't have only a single receptacle connected. A duplex
> outlet is 2 receptacles.
>
>
> 15A receptacles are rated 20A feedthrough and 20A total combined load from
> both outlets on a duplex receptacle. Since they are allowed on 20A
> circuits, they will be connected and used that way. The UL standard
> recognizes the likely usage.
>
> --
> bud--
True enough if you look at the UL rating, but about 15 years ago or so the
NEC sought to end the practice of "backwiring" outlets as a way of making up
#12 wire. That is when manufacturers reduced the hole size on the back of
devices so that a 12 would no longer fit. In doing so they made it kind of a
"grey area" to use the side screws to carry the circuit through for #12
wire. (I'm sure the intent was for #12 on a 20 amp circuit.) That is why the
backwire versions that incorporate a torqued plate have become so popular.
Whan you use two wires under the same plate, the receptacle carries no feed
through current. Anything more than two wires "should" be pigtailed if you
want to be anywhere near proper about it. It is half-assed to rely on a
device and it's terminations for the integrity of a circuit.
| |
| Randell Tarin 2007-03-07, 8:25 pm |
| All of that being said and the 12 AWG being run, it would be better/best
to have 20 AMP receptacles on a 20 AMP breaker....correct.
Is an Arc-Fault breaker for a bedroom overdoing it? I know it's now
code, but really...
Long Ranger wrote:
> "Bud--" <remove.BudNews@isp.com> wrote in message
> news:25ea4$45eedfa9$4213eb9d$16342@DIALUPUSA.NET...
>
>
>
> True enough if you look at the UL rating, but about 15 years ago or so the
> NEC sought to end the practice of "backwiring" outlets as a way of making up
> #12 wire. That is when manufacturers reduced the hole size on the back of
> devices so that a 12 would no longer fit. In doing so they made it kind of a
> "grey area" to use the side screws to carry the circuit through for #12
> wire. (I'm sure the intent was for #12 on a 20 amp circuit.) That is why the
> backwire versions that incorporate a torqued plate have become so popular.
> Whan you use two wires under the same plate, the receptacle carries no feed
> through current. Anything more than two wires "should" be pigtailed if you
> want to be anywhere near proper about it. It is half-assed to rely on a
> device and it's terminations for the integrity of a circuit.
>
>
| |
| Long Ranger 2007-03-07, 9:25 pm |
|
"Randell Tarin" <thetarins@earthlink.net> wrote in message
news:HcKHh.10335$tD2.4248@newsread1.news.pas.earthlink.net...
> All of that being said and the 12 AWG being run, it would be better/best
> to have 20 AMP receptacles on a 20 AMP breaker....correct.
The typical 20 amp circuit utilizes 15 amp outlets unless there is a reason
for a 20 amp. Probably unlikely in a bedroom, unless you are installing a
wall air unit. Then it is advisable to give it a separate circuit anyway.
You can apply a 20 amp circuit to 13 outlets, and a 15 amp circuit to 10
outlets assuming they are general purpose. The arc fault is required, so I
would install it. I am suspicious of their effectiveness, and I really
wonder if they aren't a way to jack the price up on home wiring so
manufacturers have something new to produce. They typically go on a 2-wire
circuit, although 3 wire versions are available. The three wire units I've
seen are real pricey.
| |
| Ben Miller 2007-03-08, 1:25 pm |
| "Randell Tarin" <thetarins@earthlink.net> wrote in message
news:HcKHh.10335$tD2.4248@newsread1.news.pas.earthlink.net...
> All of that being said and the 12 AWG being run, it would be better/best
> to have 20 AMP receptacles on a 20 AMP breaker....correct.
Not at all. 15A & 20A receptacles are the same device, except for the
additional right-angle slot on the 20A. As long as there is more than one
receptacle, you can put 15A receptacles on a 20A circuit. They will carry
the same current safely, and you can daisy chain either one on a 20A
circuit. You can only put 15A receptacles on a 15A circuit, however.
Any UL Listed appliance that draws over 12A (1440W) up to16A (1920W) will
have a 20A plug and won't fit in the15A receptacle. That will require a 20A
receptacle on a 20A circuit, to insure that a single appliance doesn't load
a circuit over 80%.
Ben Miller
--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com
| |
|
| Ben Miller wrote:
>
> Any UL Listed appliance that draws over 12A (1440W) up to 16A (1920W) will
> have a 20A plug and won't fit in the 15A receptacle. That will require a 20A
> receptacle on a 20A circuit, to insure that a single appliance doesn't load
> a circuit over 80%.
>
A few code cycles back there were several proposals to change the
prohibition of plugging in loads over 80% (may have been for 210.21-B-2).
One argument was that some UL listed devices, like hair dryers, with
current draw of 12-15A can have 15A plugs - UL thinks plug-in devices at
100% are OK. (The CMP response was 'we are right, they are wrong'.)
(Another argument was that the 80% rule generally applies only to
continuous loads in the NEC.)
--
bud--
| |
|
| Long Ranger wrote:
[color=darkred]
>
>
> True enough if you look at the UL rating, but about 15 years ago or so the
> NEC sought to end the practice of "backwiring" outlets as a way of making up
> #12 wire. That is when manufacturers reduced the hole size on the back of
> devices so that a 12 would no longer fit. In doing so they made it kind of a
> "grey area" to use the side screws to carry the circuit through for #12
> wire. (I'm sure the intent was for #12 on a 20 amp circuit.) That is why the
> backwire versions that incorporate a torqued plate have become so popular.
> Whan you use two wires under the same plate, the receptacle carries no feed
> through current. Anything more than two wires "should" be pigtailed if you
> want to be anywhere near proper about it. It is half-assed to rely on a
> device and it's terminations for the integrity of a circuit.
>
I have yet to see anyone who recommends backstab connections, and
recommendations on newsgroups are commonly made to eliminate existing
backstabs, especially for through wiring. (Not to imply you recommend them.)
20A side wired feedthrough is within the design and testing of
receptacles and is commonly used. The only reason to have 2 screws is
for feedthrough. I am not aware of significant problems and don't see
how using feedthrough is "half-assed", particularly in residential.
"Torque plate" connections are nice and and are likely on spec grade
devices that are higher quality overall.
--
bud--
| |
| Ben Miller 2007-03-08, 1:25 pm |
| "Bud--" <remove.BudNews@isp.com> wrote in message
news:8c446$45f03f64$4213ea9e$1159@DIALUPUSA.NET...
> I have yet to see anyone who recommends backstab connections, and
> recommendations on newsgroups are commonly made to eliminate existing
> backstabs, especially for through wiring. (Not to imply you recommend
> them.)
>
> 20A side wired feedthrough is within the design and testing of receptacles
> and is commonly used. The only reason to have 2 screws is for feedthrough.
> I am not aware of significant problems and don't see how using feedthrough
> is "half-assed", particularly in residential.
>
> "Torque plate" connections are nice and and are likely on spec grade
> devices that are higher quality overall.
>
> --
> bud--
I agree, but let's differentiate between "backstabs" , which are bad news,
and rear entry into clamping screws, which are OK.
Ben Miller
--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com
| |
| gfretwell@aol.com 2007-03-09, 3:25 am |
| On Thu, 08 Mar 2007 10:47:07 -0600, Bud-- <remove.BudNews@isp.com>
wrote:
>Ben Miller wrote:
>
>A few code cycles back there were several proposals to change the
>prohibition of plugging in loads over 80% (may have been for 210.21-B-2).
>
>One argument was that some UL listed devices, like hair dryers, with
>current draw of 12-15A can have 15A plugs - UL thinks plug-in devices at
>100% are OK. (The CMP response was 'we are right, they are wrong'.)
>
>(Another argument was that the 80% rule generally applies only to
>continuous loads in the NEC.)
These hair dryers are nowhere as big a load as they brag about. It is
like air compressor stickers
http://members.aol.com/gfretwell/hairdryer.jpg
| |
| Randell Tarin 2007-03-09, 8:25 pm |
| gfretwell@aol.com wrote:[color=darkred]
> On Thu, 08 Mar 2007 10:47:07 -0600, Bud-- <remove.BudNews@isp.com>
> wrote:
>
>
[color=darkred]
I think the prudent measure would be to have everything rated at 20A.
This is good insurance against whatever future energy hogs come on the
scene.
| |
| Paul Hovnanian P.E. 2007-03-10, 3:25 am |
| Ben Miller wrote:
>
> "Bud--" <remove.BudNews@isp.com> wrote in message
> news:8c446$45f03f64$4213ea9e$1159@DIALUPUSA.NET...
>
> I agree, but let's differentiate between "backstabs" , which are bad news,
> and rear entry into clamping screws, which are OK.
I think that's what he meant by 'torque plate', although I'm not
familiar with that exact term.
> Ben Miller
>
> --
> Benjamin D. Miller, PE
> B. MILLER ENGINEERING
> www.bmillerengineering.com
--
Paul Hovnanian mailto:Paul@Hovnanian.com
------------------------------------------------------------------
Quantum Mechanics: The dreams stuff is made of.
| |
|
| Paul Hovnanian P.E. wrote:
> Ben Miller wrote:
>
>
>
> I think that's what he meant by 'torque plate', although I'm not
> familiar with that exact term.
>
Yes, that is what I meant. I picked up "torque plate" from a descriptive
term in Long Ranger's post. No reason to be familiar unless you
carefully read back in the thread. Sorry for not being clearer.
-----
Everybody seems to agree "backstabs" are not reliable (including me).
Anyone have an idea why they are allowed by UL?
--
bud--
| |
| Long Ranger 2007-03-10, 1:25 pm |
|
"Bud--" <remove.BudNews@isp.com> wrote in message
news:ad25b$45f26936$4213eaaa$16906@DIALUPUSA.NET...
> Paul Hovnanian P.E. wrote:
[color=darkred]
>
> Yes, that is what I meant. I picked up "torque plate" from a descriptive
> term in Long Ranger's post. No reason to be familiar unless you carefully
> read back in the thread. Sorry for not being clearer.
>
> -----
> Everybody seems to agree "backstabs" are not reliable (including me).
> Anyone have an idea why they are allowed by UL?
>
> --
> bud--
I still say pigtailing the wire is superior and that using a device to carry
your circuit is a poor substitute. The wire itself is much more robust than
connecting across that phony little set of screws that exist on a .79 cent
receptacle. I can't say I've seen many instances of that two screw
connection failing, but there have been some. On a spec-grade receptacle, it
seems a bit more plausible, but I have used some residential grade devices
that stripped out before I thought they had enough torque on them to make a
good connection.
On the subject of "backstabs" I see that the residential guys around here
are switching almost exclusively to "Wago" stab-in connectors. It seems like
an extension of the backwire idea applied to wire connectors. I have a
friend who contracts tract homes and he says it's all they use, barring
connections that involve fine strand. He showed me some, and they go from
2-wire up to 8-wire configurations, with a max of #12 for size. Doesn't seem
like a step in the right direction to me, but maybe they have perfected the
idea somehow.
| |
| phil-news-nospam@ipal.net 2007-03-12, 5:25 pm |
| On Sat, 10 Mar 2007 01:52:24 GMT Randell Tarin <thetarins@earthlink.net> wrote:
| gfretwell@aol.com wrote:
|> On Thu, 08 Mar 2007 10:47:07 -0600, Bud-- <remove.BudNews@isp.com>
|> wrote:
|>
|>
|>>Ben Miller wrote:
|
|>>One argument was that some UL listed devices, like hair dryers, with
|>>current draw of 12-15A can have 15A plugs - UL thinks plug-in devices at
|>>100% are OK. (The CMP response was 'we are right, they are wrong'.)
|
| I think the prudent measure would be to have everything rated at 20A.
| This is good insurance against whatever future energy hogs come on the
| scene.
Like heating elements used as light sources?
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2007-03-12-1450@ipal.net |
|------------------------------------/-------------------------------------|
| |
| phil-news-nospam@ipal.net 2007-03-12, 5:25 pm |
| On Sat, 10 Mar 2007 15:47:12 GMT Long Ranger <worpylorp@mindspring.com> wrote:
| I still say pigtailing the wire is superior and that using a device to carry
| your circuit is a poor substitute. The wire itself is much more robust than
| connecting across that phony little set of screws that exist on a .79 cent
| receptacle. I can't say I've seen many instances of that two screw
| connection failing, but there have been some. On a spec-grade receptacle, it
| seems a bit more plausible, but I have used some residential grade devices
| that stripped out before I thought they had enough torque on them to make a
| good connection.
I've seen pigtails fail more. I think any failure is the result of some
aspect of not being done properly.
| On the subject of "backstabs" I see that the residential guys around here
| are switching almost exclusively to "Wago" stab-in connectors. It seems like
| an extension of the backwire idea applied to wire connectors. I have a
| friend who contracts tract homes and he says it's all they use, barring
| connections that involve fine strand. He showed me some, and they go from
| 2-wire up to 8-wire configurations, with a max of #12 for size. Doesn't seem
| like a step in the right direction to me, but maybe they have perfected the
| idea somehow.
The idea is pay the electrician less.
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2007-03-12-1452@ipal.net |
|------------------------------------/-------------------------------------|
| |
| Randell Tarin 2007-03-12, 5:25 pm |
| phil-news-nospam@ipal.net wrote:
> | I think the prudent measure would be to have everything rated at 20A.
> | This is good insurance against whatever future energy hogs come on the
> | scene.
>
> Like heating elements used as light sources?
How else I'm I supposed to power my bedside rotissiere? Let's not
forget the digital clock radio that doubles as a water bed/hot tub
heater. ;-)
I'm just saying it's easier to prewire than rewire.
| |
| phil-news-nospam@ipal.net 2007-03-14, 5:25 pm |
| On Mon, 12 Mar 2007 20:01:03 GMT Randell Tarin <thetarins@earthlink.net> wrote:
| phil-news-nospam@ipal.net wrote:
|
|> | I think the prudent measure would be to have everything rated at 20A.
|> | This is good insurance against whatever future energy hogs come on the
|> | scene.
|>
|> Like heating elements used as light sources?
|
|
| How else I'm I supposed to power my bedside rotissiere? Let's not
| forget the digital clock radio that doubles as a water bed/hot tub
| heater. ;-)
|
| I'm just saying it's easier to prewire than rewire.
I do agree. But I just hope we try better at avoiding energy hogs in the
future. The typical home should never need more than 200A service and
should do fine on even 100A. IMHO, if they want more than 48 kVA, they
should be required to take a higher voltage or three phase to get it.
I'm all for charging commercial power rates for all residential power
usage for the amount that exceeds the median for homes in that climate
zone (determined county by county or city by city). That should help
to discourage waste.
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2007-03-14-1441@ipal.net |
|------------------------------------/-------------------------------------|
| |
| gfretwell@aol.com 2007-03-15, 3:25 am |
| On 14 Mar 2007 19:47:43 GMT, phil-news-nospam@ipal.net wrote:
>I'm all for charging commercial power rates for all residential power
>usage for the amount that exceeds the median for homes in that climate
>zone (determined county by county or city by city). That should help
>to discourage waste.
I am taking my lead from Al Gore. I may not be able to use the quarter
of a gigawatt hour he uses in a year but I will do my best.
| |
|
| gfretwell@aol.com wrote:
> On 14 Mar 2007 19:47:43 GMT, phil-news-nospam@ipal.net wrote:
>
>
>
>
>
> I am taking my lead from Al Gore. I may not be able to use the quarter
> of a gigawatt hour he uses in a year but I will do my best.
You need to go back to school to get your
Doctorate of Hypocrisy degree before competing with him.
Ed
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