15 Amp devices in a 20 Amp circuit

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jbwhite

Senior Member
Re: 15 Amp devices in a 20 Amp circuit

Originally posted by kbsparky:
...for what it is worth, if a 15 amp rec was not safe to install on a 20 amp circuit then their would be some mention of this practice being not allowed in the code...
I have no problem with installing a 15 Amp outlet on a 20 Amp circuit here.

This discussion was not about installing a 15 Amp receptacle on a 20 Amp circuit, but rather in that circuit as part of its current-carrying conductors.

Sorry if that was not clear in the thread title, I have modified it by changing the word "on" to "in" for clarification.
ever since i was a young padawan apprentice, we were taught to pig tail 15 amp recs on kitchen circuits.

[ November 26, 2005, 10:07 PM: Message edited by: jbwhite ]
 

davedottcom

Senior Member
Re: 15 Amp devices in a 20 Amp circuit

</font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">210.21(B)(3) Allows 15 amp recps. to be used on 20 amp circuits</font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">the UL listing according to Iwire's report shows it was investigated for having multiple conductors attached to it.</font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">If the UL "Investigation" did not include 20 amp loads, the NEC would not allow the use of the 15 amp device on 20 amp circuits.</font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">The NEC makes it very clear that it's acceptable...again, back to 210.21(B)(3)</font>
<font size="2" face="Verdana, Helvetica, sans-serif">
I highly doubt the NEC panel would so blatantly approve of the use of 15 amp devices on 20 amp circuits if the UL investigation did not include 20 amp loads during their multiple conductor testing.

Let us know if UL says anything different.

;)
Dave
 

JohnE

Senior Member
Location
Milford, MA
Re: 15 Amp devices in a 20 Amp circuit

Originally posted by kbsparky:
I can not see where they say that 15 Amp devices were tested as part of a 20 Amp circuit. Their text needs to be more specific for me to accept that as the only written standard on which it would be acceptable. Taking that one step further, and also referencing my original post:
Why don't the manufacturers of the 15 Amp devices simply state that they are approved for use as part of a 20 Amp circuit, like they do with their GFI devices???

I figure they can't because they aren't.
Does UL say that 20 amp devices are permitted as part of a 20 amp circuit? "As part of" being your operative phrase. Implying that the tabs of the receptacle are rated for 20 amps.
I would guess that GFI receptacles have this phrasing to note that the GFI is "monitoring" the ground fault for the 20 amp rating of the circuit, but that the actual receptacle within the GFI device is rated for 15 amps.
I don't think the wording is necessary for 15-20 amp duplex receptacles, as UL has addressed it as others have mentioned.
 

charlie b

Moderator
Staff member
Location
Seattle, WA
Occupation
Electrical Engineer
Re: 15 Amp devices in a 20 Amp circuit

I got into this one a bit late. All I can offer is that I agree that this is a valid question, and that I have not yet seen a definitive answer. Perhaps there is no definitive answer to be found. So grab your lance and go after that windmill. Good luck.
 

kbsparky

Senior Member
Location
Delmarva, USA
Re: 15 Amp devices in a 20 Amp circuit

Charlie, does Mike get to read any of the posts on the boards here? Or could you or Ryan copy this thread and ask him to look into this?

I've seen more than one instance where an interpretation of the Code depended on the use of a single word in a section. In this case, the word used in the Code was to: "Where connected to..." which implies that the circuit would be continuous without the connection of said device(s).


I know that he has much more access to resources and data than I do, and would like to see if he could address this issue with the folks over at UL as well as with some manufacturers.

I would even like to see a follow-up in EC&M if possible as that was the source of the original inquiry.

-Ken
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Re: 15 Amp devices in a 20 Amp circuit

It is my opinion that receptacle ratings are based on the slot shape, and not just the conductive parts' current capacity. This applies to 250-volt devices as well as 125-volt ones.

For a given grade (such as residential, commercial, spec., etc.), the internal parts of 15- and 20-amp devices are the same. The "triple-wipe" contacts fit either blade orientation.

Think of the slot shape as a rejection feature, like panels that reject tandem breakers. A 20-amp receptacle accepts both 15- and 20-amp plugs; the 15-amp receptacle, only the 15-amp plug.

The slot shape indicates the circuit's ampacity, not necessarily the device's. While you can find 20-amp receptacles that reject 15-amp plugs, the vast majority have the T-shaped slot.

Look at your typical range and dryer receptacles and plugs, especially the convertible 30/50-amp plugs. If you use the L-shaped ground pin, the plug is still physically capable of 50 amps.
 

hardworkingstiff

Senior Member
Location
Wilmington, NC
Re: 15 Amp devices in a 20 Amp circuit

Originally posted by jbwhite:
i agree with you iwire, for what it is worth, if a 15 amp rec was not safe to install on a 20 amp circuit then their would be some mention of this practice being not allowed in the code.
The 15 amp receptacle will only accept loads rated at 15 amps or less. The breaker is to protect the wire, not the load. I believe that is why you are allowed to install the 15 amp receptacle on the 20 amp circuit.

I agree with the premise kbsparky has put forth. I believe it would be incorrect to use a 15 amp receptacle to "feed through" the power for a 20 amp circuit.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Re: 15 Amp devices in a 20 Amp circuit

I have asked UL to clarify this. Not sure how long it will be before they get back to me.
Don
 

hurk27

Senior Member
Re: 15 Amp devices in a 20 Amp circuit

BY Paul: they stopped making 20 amp back stabs about 5 to 8 years ago because the back stab would not handle the load under some installation conditions (read that how you may). Some electricians bought up all they could in this area and used them while they could.
Paul The reason UL stopped allowing #12awg to be used in the push in holes was because of the wire bending space in a receptacle box was causing the #12awg to push to one side and not make good contact with the teeth of the back stab contacts. They still allow push in type contacts for #12awg and even #10 for that matter when there is more space so the the bending of the wire doesn't put pressure on the contacts. Look at the push in wire nuts and even terminal strips in control panels, you can buy breakers up to 30 amps that have push in holes. This question has come up allot at many of the national IAEI meetings and this was the answer given by UL.
Just a FYI not to side track the very good question of the OP.
 

charlie b

Moderator
Staff member
Location
Seattle, WA
Occupation
Electrical Engineer
Re: 15 Amp devices in a 20 Amp circuit

Originally posted by kbsparky: Charlie, does Mike get to read any of the posts on the boards here? Or could you or Ryan copy this thread and ask him to look into this?
Mike is a member of the Forum, and "gets to read" any or all of the material that is posted here. But he is on the road a great deal. He also gets hundreds, if not thousands, of email messages every day. I'll not take it upon myself to add to his work load. I think the efforts by Don to contact UL are the best bet for a resolution.
Originally posted by kbsparky: I would even like to see a follow-up in EC&M if possible as that was the source of the original inquiry.
You would have to take that up with EC&M.
 

Mike03a3

Senior Member
Location
Virginia
Re: 15 Amp devices in a 20 Amp circuit

We are talking duplex recpts.,the top recpt is rated for 15a and the bottom of the same recpt. is rated 15a. Now why can't I plug two 10a loads into this one 15a rated recpt. that is on a 20a circuit?
In that scenario, the feed-through tabs are only carrying 10 amps, the other 10 are going straight out the 12ga wire on the terminals.

GFI receptacles go out of their way to point out the fact they are listed for 20 Amp feed-through circuits. I see no such rating or claim on standard 15 Amp receptacles.
Which makes perfect sense, since the GFI is designed with "load" terminals so that it can protect an entire circuit.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Re: 15 Amp devices in a 20 Amp circuit

In my opinion, the reason 15-amp GFCI's are rated for 20 amps feed-thru is because it's known and accepted to place 15-amp (non-single)-receptacles on 20-amp circuits.

Standard receptacles do not need this notation because they are passive devices. I firmly believe that 15-amp receptcales are perfectly capable of passing 20 amps.
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: 15 Amp devices in a 20 Amp circuit

I would say that GFCIs have the feed through rating on them as they are a 'controller' along with being a receptacle. :)
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: 15 Amp devices in a 20 Amp circuit

Originally posted by kbsparky:
The Code is very specific about not exceeding the ratings of listed devices.
kb I am not being a wise guy here just asking a real question.

Where is the NEC very specific about exceeding the current ratings of listed devices?

Is there a code section you can cite?

[ November 28, 2005, 05:34 PM: Message edited by: iwire ]
 

charlie b

Moderator
Staff member
Location
Seattle, WA
Occupation
Electrical Engineer
Re: 15 Amp devices in a 20 Amp circuit

Originally posted by iwire: Where is the NEC very specific about exceeding the current ratings of listed devices? Is there a code section you can cite?
I don't suppose 110.3(B) would count? Do the UL listings of such devices as receptacles have specific limitations on their current ratings? Is it safe to infer that a 15 amp receptacle has a limit of 15 amps as part of its UL listing?
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: 15 Amp devices in a 20 Amp circuit

Originally posted by charlie b:
I don't suppose 110.3(B) would count?
I guess it could but at the same time we have no problem supplying a 60 amp fused disconnect with a 100 amp feeder.

I understand the subtle difference as I will not be running the 100 amp feed through the switch.

However both the 60 amp fusible switch and the 15 amp duplex will be connected to a supply rated higher than the rating of the equipment. Which would seem to violate 110.3(B). ;)

No answers, just confusion.
 

kbsparky

Senior Member
Location
Delmarva, USA
Re: 15 Amp devices in a 20 Amp circuit

...However both the 60 amp fusible switch and the 15 amp duplex will be connected to a supply rated higher than the rating of the equipment. Which would seem to violate 110.3(B). ;)
Not really. Because the fuses installed in that 60 Amp switch will limit the amount of current that can safely pass to 60 Amps. Now using an unfused switch with a 100 Amp feeder would be a problem, IMHO.
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: 15 Amp devices in a 20 Amp circuit

Originally posted by kbsparky:
Not really. Because the fuses installed in that 60 Amp switch will limit the amount of current that can safely pass to 60 Amps. Now using an unfused switch with a 100 Amp feeder would be a problem, IMHO.
I understand the point you are making but please humor me.


Where is the language in the NEC that allows the fusible disconnect or disallows the receptacle.

Or more to the point where is the section in the NEC that tells us that a receptacle must be supplied within it's current rating at all?
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: 15 Amp devices in a 20 Amp circuit

Originally posted by iwire:
Or more to the point where is the section in the NEC that tells us that a receptacle must be supplied within it's current rating at all?
Let me add when "in" the circuit or "connected" to the circuit.
 
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