15 Amp vs. 20 Amp

[larrybud2002]

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

Yes.

[William.Deans]

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

[Ray]

Can 15 amp receptacles be used in a 20 Amp circuit ??

Does this also apply to light switches ???

Thanks

[William.Deans]

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

[Terry]

I'm OK about size of wiring (#14 AWG for 15 amp and #12 AWG for 20 amp and 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

[Edwin Pawlowski]

No, very dangerous but you can do the opposite.

Yes, it does apply to switches also.

[Tekkie®]

HorneTD posted for all of us... I don't top post - see either inline or at bottom.

You and I both know where they coming from: unknowledgeable guessing.

[Rick]

Yes, as long as there is more than one receptical on that circuit.

[Bob Vaughan]

Yes, 15 amp receptacles may be used on 20 amp circuits except for circuits dedicated to a particular purpose (ie: window air conditioners), where the entire load on the circuit is drawn thru a single outlet.

The circuit wiring must be sized for the overcurrent protection (ie: 12awg for 20 amp circuits) throughout the circuit. (no 14awg pigtails to feed

15amp outlets).

ditto for light switches, so long as the connected load does not exceed

80% of the switch rating. (if you are actually switching 15amp loads, you really need to use a 20amp switch..) In reality, you're probably not going to be switching 1440watts worth of lighting on a single switch..)

[Rick]

loads,

switch..)

Although, unless the Code has changed since my latest book (1999), the

80% rule for switches applies to motor loads. But your point is well taken!

[Rick]

...............

probably used a

conservatively

A 20A plug has a different blade arrangement so it can't be inserted into a 15A receptacle

[Rick]

...............

probably used a

conservatively

Not quite sure what you're asking about on the "dedicated" outlet. A duplex receptacle is not a "single" outlet, though..

[HorneTD]

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.

[HorneTD]

I don't know were some of these completely erroneous answers are coming from but it isn't from the US National Electric Code.

"210.21 Outlet Devices. Outlet devices shall have an ampere rating that is not less than the load to be served and shall comply with 210.21(A) and (B). (B) Receptacles. (1) Single Receptacle on an Individual Branch Circuit. A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit. (2) Total Cord-and-Plug-Connected Load. Where connected to a branch circuit supplying two or more receptacles or outlets, a receptacle shall not supply a total cord-and-plug-connected load in excess of the maximum specified in Table 210.21(B)(2).

Table 210.21(B)(2) Maximum Cord-and-Plug-Connected Load to Receptacle Circuit Rating Receptacle Rating Maximum Load (Amperes) (Amperes) (Amperes)

15 or 20 15 12 20 20 16 30 30 24

(3) Receptacle Ratings. Where connected to a branch circuit supplying two or more receptacles or outlets, receptacle ratings shall conform to the values listed in Table 210.21(B)(3), or where larger than 50 amperes, the receptacle rating shall not be less than the branch-circuit rating. Exception No. 1: Receptacles for one or more cord-and-plug-connected arc welders shall be permitted to have ampere ratings not less than the minimum branch-circuit conductor ampacity permitted by 630.11(A) or (B) as applicable for arc welders. Exception No. 2: The ampere rating of a receptacle installed for electric discharge lighting shall be permitted to be based on 410.30(C).

Table 210.21(B)(3) Receptacle Ratings for Various Size Circuits Circuit Rating (Amperes) Receptacle Rating (Amperes)

15 Not over 15 20 15 or 20 30 30 40 40 or 50 50 50

404.14 Rating and Use of Snap Switches. Snap switches shall be used within their ratings and as indicated in

404.14(A) through (D). FPN No. 1:For switches on signs and outline lighting, see 600.6. FPN No. 2:For switches controlling motors, see 430.83, 430.109, and 430.110. (A) Alternating Current General-Use Snap Switch. A form of general-use snap switch suitable only for use on ac circuits for controlling the following: (1) Resistive and inductive loads, including electric-discharge lamps, not exceeding the ampere rating of the switch at the voltage involved (2) Tungsten-filament lamp loads not exceeding the ampere rating of the switch at 120 volts (3) Motor loads not exceeding 80 percent of the ampere rating of the switch at its rated voltage (B) Alternating-Current or Direct-Current General-Use Snap Switch. A form of general-use snap switch suitable for use on either ac or dc circuits for controlling the following: (1) Resistive loads not exceeding the ampere rating of the switch at the voltage applied. (2) Inductive loads not exceeding 50 percent of the ampere rating of the switch at the applied voltage. Switches rated in horsepower are suitable for controlling motor loads within their rating at the voltage applied. (3) Tungsten-filament lamp loads not exceeding the ampere rating of the switch at the applied voltage if T-rated. (C) CO/ALR Snap Switches. Snap switches rated 20 amperes or less directly connected to aluminum conductors shall be listed and marked CO/ALR. (D) Alternating-Current Specific-Use Snap Switches Rated for 347 Volts..." Snipped as not applicable to home repair. Copyright 2002 National Fire Protection Association

[CL (dnoyeB) Gilbert]

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.

[CL (dnoyeB) Gilbert]

Could you interpret these regulations please? What I hear from many of these folks we would never do in the automotive world. In the auto world our circuit protection is for 'failure conditions'. Most people here seem to be protecting for normal conditions.

For instance, we would not care about keying. Cigar lighter receptacle must be able to pass a load equivalent to the rating of its circuit protection. Nothing less. It has nothing to do with the likelyhood of the device plugged in.

Same with switches. It could be a switch with a .35A bulb on the end. If its circuit protection is 20A, then the switch itself must be rated for 20A. This is why sometimes we split circuits in two, so we can drop the rating of the protection and reduce the size of thes. It could be a switch with a .35A bt circuits in two, so we

CL Gilbert

[Chris Lewis]

According to Rick :

Not quite. Switches for "motors" (except for small ones like those in clocks) are supposed to be "horse power rated". So, not only must the switch ampacity be sufficient, the switch must ALSO be rated for the HP the motor generates. Which is why you don't use ordinary wall switches for large motors.

[Rick]

Unless the motor is 2 HP or less and a general use snap switch only for use on AC, according to 430-83 C 2...

[Chris Lewis]

According to CL (dnoyeB) Gilbert :

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.

[Phil Munro]

Find a 15 Amp receptacle in the store, one that is in a box with some 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