15 Amp vs. 20 Amp

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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..)
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wrote:

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!
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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.
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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...
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Ray wrote:

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

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Tekkie


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Tekkie wrote:

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
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