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When wiring 15A-rated outlet receptacles on a 20A circuit, is it acceptable to use the tabs & screws to chain the circuit from one outlet to the next?

My instinct to overengineer says to use pigtails to pass the power to the next outlet and wire the receptacle, but this takes up more space in the box. So is the tab on a 15A outlet sufficient for handling a 20A load though a series of outlets? if so, why?

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2 Answers 2

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Yes it is sufficient.

A 15A receptacle is designed such that an appliance with a 20A plug should not be able to plug into it. This means that at most under normal operating conditions of a 15A appliance, that the receptacle itself will only draw 15A. If the circuit shorts then the breaker will kick at 20A however.

The tab of a 15A receptacle is designed to handle a 20A load.

EDIT for clarification above: A duplex 15A receptacle contains a tab that connects the hot lead to the hot load. This allows the receptacle to carry the load of another outlet by wiring the lead of Outlet(2) to the load of Receptacle(1). When you break off this hot tab then you are specifically wiring for a switch to control only of the receptacles of the outlet, or you are specifically wiring for each receptacle to have its own circuit on a shared neutral. For two circuits to be wired to a single receptacle on a shared neutral, then you need to ensure that the breakers are on different service legs or you risk overloading the neutral. If you also break the neutral tab then you are wiring the receptacle to have two separate circuits each with its own dedicated neutral. These should be considered fringe cases for residential so it is probably best not to break the tabs if not needed so as to avoid confusing future DIY'ers and licensed electricians. Every time a DIY'er or electrician gets confused then they are potentially risking themselves.

The NEC states that this is acceptable as long as:

  1. The wire is 12 AWG sized for a 20A circuit

  2. There is more than one receptacle on the circuit.

It is important to note that under no circumstances should you install a single 15A receptacle onto a dedicated 20A circuit. This is against code.

210.21(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.

(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.

Table:

Circuit Rating (Amperes)
Receptacle Rating
(Amperes)
15 Not over 15
20 15 or 20
30 30
40 40 or 50
50 50

In conclusion, a standard 15A receptacle that one would buy in your hardware store is quality tested and approved to comply with all NEC codes to be legally sold in the United States. If the tab couldn't handle a 20A load without overheating then they would call this out specifically.

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The important part of your answer is "The tab is designed to handle a 20A load to a 20A outlet." But these are 15A outlets, that is the essence of the question. Is that just a typo, since the other parts of your answer seem to say it's OK (e.g. "in conclusion"). I am not convinced that because a 15A outlet can be installed on a 20A branch circuit, that implies that any way of wiring them would be correct. (I'd say it seems intuitive, but I'm looking for a hard answer not just a guess, e.g. some reference that says 15A plugs must be designed to carry 20A current between the screws). –  jamietre Nov 19 '12 at 17:33
    
Regarding your edit I think it might be more clear if you just said "The tab of a 15A outlet is designed to handle a 20A load." Is that correct? If so then it answers my question. –  jamietre Nov 19 '12 at 17:53
    
@jamietre I added clarification to my statement in the answer. It is not a typo. According to NEC, I can wire the lead of a 20A outlet directly to the load of a 15A outlet on a 20A circuit. The tabs are there and can be removed for the reasons stated in my edit and for no other reasons. Wiring outlets in a circuit load-to-lead is considered standard for a circuit, so if the tabs presented an inherent problem then Table 210.21(b)(3) wouldn't explicity allow 15A receptacles on a 20A circuit. To explicitly call out what you are asking for is redundant. –  maple_shaft Nov 19 '12 at 17:56
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FYI: just found this electricalknowledge.com/forum/archives/1448.asp -- very long conversation to indicate that feed-through is 20A as well. Then you also have a couple guys saying they always uses pigtails anyway.. :-/ –  jamietre Nov 19 '12 at 18:11
    
@jamietre That is a good point though that on older outlets you probably shouldn't just assume this. I still believe though that since pigtailing isn't the common way to do this with modern electrical supplies that opting to do this may confuse a DIY'er. –  maple_shaft Nov 19 '12 at 18:26

You shouldn't use 15A outlets on a 20A circuit. The 15A outlets are only rated for 15A. There is the risk for overheating and potential fire at the 15A circuit location before the 20A breaker would pop.

I always like to use pigtails and the inspector in my area agrees. It's never happened to me, but if an outlet fails and you don't use pigtails, the rest of the outlets downstream could be affected.

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15A receptacles are allowed on 20A circuits (see: diy.stackexchange.com/questions/12115/…). They are meant for devices that will only draw 15A (so don't plug a 20A device into them but that should be hard since hopefully the plug will not fit). –  auujay Nov 19 '12 at 15:49
    
The NEC explicitly allows 15A receptacles on 20A branch circuits. Almost every modern kitchen is wired this way - at least I've rarely seen a 20A outlet outside a workshop and most kitchen outlets are on 20A circuits. –  jamietre Nov 19 '12 at 16:08
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Btw I have nothing against using pigtails, but I always feel simpler is better. There are fewer things to fail with fewer points of contact and less wire. If the outlet is designed for this, and it is legal, than I feel it is preferable. –  jamietre Nov 19 '12 at 16:21
    
@jamietre If you are aware that it is designed for this then why are you asking the question? I am just curious. –  maple_shaft Nov 19 '12 at 17:20
    
I am not sure if it's designed for this. I said "if." I know you can use 15A outlets on 20 circuits. I don't know if you can use the two terminal posts to chain them on a 20A circuit. That is my question -- whether you must use pigtails, or can chain them. Basically, is the tab designed to carry 20A. –  jamietre Nov 19 '12 at 17:28

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