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Wire size vs. Breaker Size---Followup Question

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.
Reply to
Randell Tarin
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#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).
Reply to
Long Ranger
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.
Reply to
Randell Tarin
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--
Reply to
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.
Reply to
Long Ranger
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...
L>>L>>
Reply to
Randell Tarin
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.
Reply to
Long Ranger
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
Reply to
Ben Miller
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--
Reply to
Bud--
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--
Reply to
Bud--
I agree, but let's differentiate between "backstabs" , which are bad news, and rear entry into clamping screws, which are OK.
Ben Miller
Reply to
Ben Miller
These hair dryers are nowhere as big a load as they brag about. It is like air compressor stickers
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Reply to
gfretwell
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.
Reply to
Randell Tarin
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--
Reply to
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.
Reply to
Long Ranger
| snipped-for-privacy@aol.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?
Reply to
phil-news-nospam
| 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.
Reply to
phil-news-nospam
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.
Reply to
Randell Tarin

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