15 Amp vs. 20 Amp

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Can 15 amp receptacles be used in a 20 Amp circuit ??
Does this also apply to light switches ???
Thanks
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Ray wrote:

No. Doing so would mean that you could plug in a device that overloads the receptacle.

Yes.
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snipped-for-privacy@yahoo.com wrote:

Sorry Larry but you are wrong.
Fifteen ampere receptacles that are listed by Underwriters Laboratories have been tested to pass through twenty amperes. What is fifteen ampere about the receptacles is the blade pattern that they are built with. Since no UL listed portable device that draws more than fifteen amperes is built with a fifteen ampere cord set your concern is unfounded. The US NEC specifically permits multiple fifteen ampere receptacles on a twenty ampere circuit.
There are switches available at most venders that are only rated at ten amperes. The smallest commonly available breaker is fifteen amperes. Switches need only be rated for the load they control. The US NEC does not require them to be able to open the entire ampacity of the branch circuit that supplies them.
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Greetings HorneTD,
"What is fifteen ampere about the receptacles is the blade pattern that they are built with. "
Does this mean that everything else about the receptacle is 20 amps? If so would it be safe to run 16 amps through a 15 amp receptacle on a 20 amp circuit? This is contrary to what I have heard but I have never read anything either way. I know the plug of a UL listed device wouldn't fit but imagine a 16 amp device with a 20 amp plug accessing the 15 amp receptacle through a perfectly safe (although not UL listed) 20 amp to 15 amp plug style adapter.
Thank you for your time, William
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snipped-for-privacy@wdeans.com wrote:

I like to know that answer as well. Is a 15amp receptacle the same as a 20amp receptacle except for the keying? I would bet the answer is yes.
The breaker is to protect the wiring 'system' which includes switches and receptacles. A 20amp circuit can pass more current than a 15amp receptacle. So consider this;
1. You have a device plugged into a 15amp receptacle. 2. Receptacle is on 20amp circuit. 3. Device fails with a resistive short. 4. Load through circuit exceeds 15amp system amount, but not 20amp system amount (say 19amps).
So now you have the receptacle passing more current that its rated for, but the breaker and wiring are fine. So I agree that the receptacle must be rated for the full 20amps if its to be plugged into a 20amp circuit, REGARDLESS of the keying.
And for this same reason I completely disagree with the 10amp switch statement. A 10amp switch on a 20amp circuit has no protection and is a danger. Can't say if its legal as I am not electrician.
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CL Gilbert
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Pretty much. In the US, 15A (or 15A/20A dual) pattern receptacles are often on 20A circuits, and the code permits/encourages it. Therefore they must be rated for it. This is a rather special case in US code.
Up until recently, Canadian code simply didn't have 20A general receptacle circuits, so, you could never have a 15A pattern receptacle on a 20A circuit. Dual-pattern 15A/20A outlets simply weren't permitted here either. So, you either had 15A circuits with 15A pattern receptacles, or 20A circuits with 20A pattern receptacles, and never the twain would meet ;-)
Rules have changed, so now we're like the US in this respect.

It's not legal in general.
There are a few explicit exceptions for things _like_ this (ie: 60A range circuit splitting to two #8 circuits for a separate cooktop + oven, or logically undersized branches in multi-motor circuits), but, rarely applicable in residential.
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CL (dnoyeB) Gilbert wrote:

writing on it. READ the specs that are either on the box or on a piece of paper IN the box. In the USA, I have found that 15 Amp receptacles are RATED at 20 Amps, but they will not allow a 20 Amp plug to be inserted because of the pattern. I'm just repeating what others have already said. Also, it is NOT true that "A 10amp switch on a 20amp circuit has no protection". It has 20 Amp protection! A lamp with flimsey lamp cord on a 20 Amp circuit is also a danger, but it does have 20 Amp protection! A short circuit on such a lamp cord will pop the 20 Amp breaker. --Phil
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CL (dnoyeB) Gilbert wrote:

them at 150% of rating, which I presume means 1/2 a 15A duples receptacle is tested at 22.5A. Posts in other threads have said that 15 & 20A receptacles are identical, including sockets for 20A plugs behind the 15A plastic face.

has to be large enough for the load. If a switch is connected to a light fixture, it would be a little difficult to lamp it at over 1200W, the rating for a 10A switch. Going through my box of salvaged switches I found several with a 10A 120V rating. The NEC is a pragmatic code; if there are problems the code is changed to deal with them.
Bud--
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Bud wrote:

And this is why we have Murphy's Law. You don't size the switch to the intended load. You size the switch so it can't cause a fire. If that fixture endures a resistive short, and its passing 15A, not enough to blow the breaker, but too much for the switch, you have a serious problem. So I guess NEC needs an updating wrt/ Murphy's Law.
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A look at the Leviton and Cooper product lineups show all residential switches to be rated at 15 or 20 A. From the Leviton technical reference, AC/DC switches can be used on motor loads that are 50% of the switch rating (80% for AC only switches) . To qualify as a motor rated switch, an AC switch is tested at 6X the full load motor HP rating current, 10X for DC, and goes through 50 make/break cycles in addition to the normal overload endurance and heating tests
Your example of a 15A resistive short is 1800 watts. I would imagine governing bodies view the chance of a 15A switch made of fire retardant materials, installed in a box, and running a few amps over it's rating starting a fire is insignificant compared to the short itself.
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Note that switches have (at least) two ratings. Interrupt rating and passthru.
Some switches may indeed have a 10A max _switch_ rating, but they're still rated 15A (or 20A) continuous. The switching rating is based on arc erosion.
_Most_ breakers have a relatively low switch rating. You're not supposed to use breakers as a power switch unless they're rated for it.
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Chris Lewis wrote:

Good point.
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CL Gilbert
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On 08/05/05 10:09 am Chris Lewis tossed the following ingredients into the ever-growing pot of cybersoup:

Huh!? If you are switching a device or devices that pull 15A while operating, it's extremely unlikely that it/they will pull less than that at switch-on time. ISTM that the switching capacity should be higher than the "running" capacity.
Perce
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The continuous rating is based around how much current can go through closed contacts without overheating.
This is radically different, and usually considerably _higher_ than you can do thousands of "make/break" cycles with.
The fact that a switch has a switch rating of 10A, with a continous current rating of 20A doesn't mean that it's deliberately designed for a circuit where this will happen all the time.
Not at all.
It just means that you limit the stuff you switch by it to 10A, but if you have a resistive short in the switched stuff that only passes 20A, the switch can safely pass the maximum current that the breaker will let through.
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Greetings,
Yes, 15 amp receptacles be used in a 20 amp circuit. The idea is that the plug shape will prevent overloading the receptacle. The 20 amp breaker will prevent gross overloading of the 15 amp receptacle if someone plugs one of those ghastly power-strips in. You can use 15 amp switches for lights. Use 20 amp switches for everything else. The full rules are actually slightly more complex than this but follow these simple guidelines and I don't think you'll run into any problems. I am also sure you are aware not to use 14 awg wire in your 20 amp circuit even if you have 15 amp switches and receptacles.
Hope this helps, William
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appropriate size of fuse/breaker), most circuits seem to have more than one outlet on them. But sounds like I could learn something from "plug shape will .............. ". Please could you explain further? Also one posting to this thread has got me thinking; any time I've put in a single or 'dedicated' outlet, fed by it's own single CB I've probably used a good quality 20 amp duplex outlet and sized everything conservatively anyway. But someone mentioned that if it is a 'single outlet' one should install only a 20 amp not a 15 amp capacity outlet! makes sense? BTW our house being slightly older has 20 amp outlet circuits and separate 15 amp lighting circuits. But in more recent construction I have seen 15 amp mixed outlet and lighting circuits using #14 AWG and 15 amp breakers as original construction (not something a householder tacked on) it appears to meet the code here. Would welcome comments and information. Terry
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A 20A plug has a different blade arrangement so it can't be inserted into a 15A receptacle
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Not quite sure what you're asking about on the "dedicated" outlet. A duplex receptacle is not a "single" outlet, though..
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No, very dangerous but you can do the opposite.
Yes, it does apply to switches also.
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Yes, as long as there is more than one receptical on that circuit.
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