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15 Amp vs. 20 Amp
Can 15 amp receptacles be used in a 20 Amp circuit ??
Does this also apply to light switches ??? Thanks |
Ray wrote: Can 15 amp receptacles be used in a 20 Amp circuit ?? No. Doing so would mean that you could plug in a device that overloads the receptacle. Does this also apply to light switches ??? Yes. |
"Ray" wrote in message news:qr2Ie.28703$mC.10857@okepread07... Can 15 amp receptacles be used in a 20 Amp circuit ?? Does this also apply to light switches ??? Thanks No, very dangerous but you can do the opposite. Yes, it does apply to switches also. |
Greetings,
Yes, 15 amp receptacles be used in a 20 amp circuit. The idea is that the plug shape will prevent overloading the receptacle. The 20 amp breaker will prevent gross overloading of the 15 amp receptacle if someone plugs one of those ghastly power-strips in. You can use 15 amp switches for lights. Use 20 amp switches for everything else. The full rules are actually slightly more complex than this but follow these simple guidelines and I don't think you'll run into any problems. I am also sure you are aware not to use 14 awg wire in your 20 amp circuit even if you have 15 amp switches and receptacles. Hope this helps, William |
"Ray" wrote in message news:qr2Ie.28703$mC.10857@okepread07... Can 15 amp receptacles be used in a 20 Amp circuit ?? Yes, as long as there is more than one receptical on that circuit. |
In article qr2Ie.28703$mC.10857@okepread07, Ray wrote:
Can 15 amp receptacles be used in a 20 Amp circuit ?? Does this also apply to light switches ??? Thanks Yes, 15 amp receptacles may be used on 20 amp circuits except for circuits dedicated to a particular purpose (ie: window air conditioners), where the entire load on the circuit is drawn thru a single outlet. The circuit wiring must be sized for the overcurrent protection (ie: 12awg for 20 amp circuits) throughout the circuit. (no 14awg pigtails to feed 15amp outlets). ditto for light switches, so long as the connected load does not exceed 80% of the switch rating. (if you are actually switching 15amp loads, you really need to use a 20amp switch..) In reality, you're probably not going to be switching 1440watts worth of lighting on a single switch..) -- -- Welcome My Son, Welcome To The Machine -- Bob Vaughan | techie @ tantivy.net | | P.O. Box 19792, Stanford, Ca 94309 | -- I am Me, I am only Me, And no one else is Me, What could be simpler? -- |
"Bob Vaughan" wrote in message ... In article qr2Ie.28703$mC.10857@okepread07, Ray wrote: Can 15 amp receptacles be used in a 20 Amp circuit ?? Does this also apply to light switches ??? Thanks 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..) 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! |
" wrote in message oups.com... Greetings, Yes, 15 amp receptacles be used in a 20 amp circuit. The idea is that the plug shape will prevent overloading the receptacle. 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 |
"Terry" wrote in message .. . " wrote in message oups.com... Greetings, Yes, 15 amp receptacles be used in a 20 amp circuit. The idea is that the plug shape will prevent overloading the receptacle. 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 A 20A plug has a different blade arrangement so it can't be inserted into a 15A receptacle |
"Terry" wrote in message .. . " wrote in message oups.com... Greetings, Yes, 15 amp receptacles be used in a 20 amp circuit. The idea is that the plug shape will prevent overloading the receptacle. 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 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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Ray wrote:
Can 15 amp receptacles be used in a 20 Amp circuit ?? Does this also apply to light switches ??? Thanks 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 -- Tom Horne Well we aren't no thin blue heroes and yet we aren't no blackguards to. We're just working men and woman most remarkable like you. |
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 |
According to Rick :
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! 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. -- Chris Lewis, Una confibula non set est It's not just anyone who gets a Starship Cruiser class named after them. |
"Chris Lewis" wrote in message ... According to Rick : 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! 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. -- 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... |
HorneTD posted for all of us...
I don't top post - see either inline or at bottom. I don't know were some of these completely erroneous answers are coming from but it isn't from the US National Electric Code. You and I both know where they coming from: unknowledgeable guessing. -- Tekkie |
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Tekkie® wrote:
HorneTD posted for all of us... I don't top post - see either inline or at bottom. I don't know were some of these completely erroneous answers are coming from but it isn't from the US National Electric Code. You and I both know where they coming from: unknowledgeable guessing. 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 the downstream wiring and switches... -- Respectfully, CL Gilbert |
According to 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. 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. 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. 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. -- Chris Lewis, Una confibula non set est It's not just anyone who gets a Starship Cruiser class named after them. |
CL (dnoyeB) Gilbert 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. .... 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. 15A receptacles are rated 20A for both halves. The UL standard tests 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. 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. As HorneTD has said in a number of threads, the NEC requires the switch 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-- |
Bud wrote:
CL (dnoyeB) Gilbert 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. .... 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. 15A receptacles are rated 20A for both halves. The UL standard tests 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. 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. As HorneTD has said in a number of threads, the NEC requires the switch 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-- 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. -- Respectfully, CL Gilbert |
"CL (dnoyeB) Gilbert" wrote in message ... Bud wrote: As HorneTD has said in a number of threads, the NEC requires the switch 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-- 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. 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. |
According to CL (dnoyeB) Gilbert :
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. 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. -- Chris Lewis, Una confibula non set est It's not just anyone who gets a Starship Cruiser class named after them. |
Chris Lewis wrote:
According to CL (dnoyeB) Gilbert : 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. 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. Good point. -- Respectfully, CL Gilbert |
On 08/05/05 10:09 am Chris Lewis tossed the following ingredients into
the ever-growing pot of cybersoup: 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. 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 |
According to Percival P. Cassidy :
On 08/05/05 10:09 am Chris Lewis tossed the following ingredients into the ever-growing pot of cybersoup: 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. 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. 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. -- Chris Lewis, Una confibula non set est It's not just anyone who gets a Starship Cruiser class named after them. |
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