15 Amp devices in a 20 Amp circuit

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kbsparky

Senior Member
Location
Delmarva, USA
In October's EC&M magazine, Mike had the following question published:

Q. an electrician installed a two-wire 20 A receptacle circuit (12 AWG) with six 15A, 125V duplex receptacles. He wired the receptacles as feed through (daisy chain) using the four screws on each device. The inspector would not accept the installation and said that he had to splice the wires and leave a pigtail, which then connected to only two screws of the receptacle. Is this an NEC requirement?

The answer given was:

A.No. Only the grounded conductor of a multiwire branch circuit is required to be pigtailed [300.13(B)]. Even on a multiwire circuit, the ungrounded conductors are not required to be pigtailed. In all cases, where equipment grounding (bonding) conductors are used, they are required to be pigtailed [250.148(B)].

I think that Mike missed the whole point of the question here. The issue of the question was not whether pigtailing was required per se, but whether using the 15 Amp devices as part of a 20 Amp circuit was allowable. Clearly, by using all the terminal screws on those 15 Amp outlets, you are in effect using the break-away tab as part of your circuit. If the device is only rated at 15 Amps, then its use as part of the 20 Amp circuit could be a violation as the inspector stipulated?

I searched the message boards here before posting this question, and found all sorts of discussions about single, duplex, and loads on outlets, etc. But in only ONE message posted by Bob [iwire] on December 14, 2004 was the statement:
The feed through rating of a 15 amp duplex receptacle is 20 amps.
I went to 2 different manufacturer's web sites, and looked up their specs on 15 Amp rated duplex outlets. Nowhere was there any reference to the "feed-thru" capacity of them being 20 Amps. Only in cases are GFI outlets is there any mention of the devices being rated for a higher feed-thru than the listed NEMA configuration.

So Bob, or anyone else here, can you provide me with some tangible reference that backs up the claim that 15 Amp duplex outlets can be installed as part of the circuit conductors on a 20 Amp circuit?

Keep in mind that I am not disputing that 15 Amp receptacles can be installed on 20 Amp circuits. Only want to know the standard by which 15 Amp devices are considered to be able to handle the load of a 20 Amp circuit when wired in this manner. Don't quote 210.21(B)(3) to me as your basis, either. That section says nothing about using the device as part of the circuit, it only says its allowable to connect a 15 Amp device to a 20 Amp circuit. It says nothing about running the circuit through the underrated device. The use of pigtails as required by the inspector in this scenerio would not be in conflict of that section of the Code.

(title of thread modified to more accurately reflect subject matter)

[ November 26, 2005, 09:34 PM: Message edited by: kbsparky ]
 

iwire

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

You have to read this carefully but the info is in here.

2005 UL White Book.
Part of
RECEPTACLES FOR PLUGS AND
ATTACHMENT PLUGS (RTRT)

Single and duplex receptacles rated 15 and 20 A that are provided with more than one set of terminals for the connection of line and neutral conductors have been investigated to feed branch circuit conductors connected to other outlets on a multi-outlet branch circuit, as follows:

Back wire (screw actuated clamp type) terminations with multiple wire access holes used concurrently to terminate more than one conductor

Side wire (binding screw) terminals used concurrently with their respective push-in (screwless) terminations to terminate more than one conductor.

Single and duplex receptacles rated 15 and 20 A that are provided with more than one set of terminals for the connection of line and neutral conductors have not been investigated to feed branch circuit conductors connected to other outlets on a multi-outlet branch circuit, as follows:

Side wire (binding screw) terminal with its associated back wire (screw actuated clamp type) terminal

Multiple conductors under a single binding screw

Multiple conductors in a single back wire hole.

[ November 26, 2005, 07:38 PM: Message edited by: iwire ]
 

jbwhite

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

iwire, that says have been investigated. what was the result of the investigation?
 

mdshunk

Senior Member
Location
Right here.
Re: 15 Amp devices in a 20 Amp circuit

Originally posted by jbwhite:
iwire, that says have been investigated. what was the result of the investigation?
"have been investigated" is UL speak for "approved".
 

jbwhite

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

Originally posted by mdshunk:
Originally posted by jbwhite:
iwire, that says have been investigated. what was the result of the investigation?
"have been investigated" is UL speak for "approved".
even more than one wire under a screw, and more than one wire in a stab hole. (i dont think that they would fit)
 

iwire

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

Originally posted by jbwhite:
even more than one wire under a screw, and more than one wire in a stab hole. (i dont think that they would fit)
No, more than one wire under a screw is part of the 'not been' list. :)
 

kbsparky

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

OK, so there was an investigation. All I see here is that 15 and 20 Amp devices were tested, and I read from that they are within their ratings.

From that report, I would fathom that a 15 Amp device could be used as part of a 15 Amp circuit. Likewise, I would postulate that a 20 Amp device would be acceptable to use as part of a 20 Amp circuit.

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.
 

iwire

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

Originally posted by jbwhite:
iwire, that says have been investigated. what was the result of the investigation?
Well first we wired it up than we plugged a bunch of stuff in until it melted. :D

What I think is this, when you buy a 15 or 20 amp duplex receptacle it has a UL listing mark on it.

Considering UL is allowing the listing mark to be placed on the receptacle and UL states it investigated the product I think it is safe to say the test results where fine.

There are also instructions included in the device boxes, I am sure the directions do not show any of the 'have not been investigated connections'.

Take a look at identical grades of 15 and 20 amp receptacles from the same manufacture and I bet you won't be able to tell any difference in construction of the terminals.
 

kbsparky

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

Take a look at identical grades of 15 and 20 amp receptacles from the same manufacture and I bet you won't be able to tell any difference in construction of the terminals.
That is not the issue here. Most manufacturers have what I would call a "cheap" type of 15 Amp receptacle, and those are much different from their standard 20 Amp offering. The fact is, their "grades" are a LOT different.

I can take a "spec grade" 15 Amp receptacle and install it on a 20 Amp circuit, and the inspector can turn it down. "But they look EXACTLY the same" I could argue, nevertheless the inspector is right in his assessment. Even IF the manufacturer used the same components in its making, with the face of the device missing the "T" slot, it still is a 15 Amp device, and as such not suitable for a 20 Amp load.
 

benaround

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

kbsparky,

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?
 

jbwhite

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

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.
 

allenwayne

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

A standard 15/20 feed thru device has feed thru capacity of #14 for back stabbing single 20`s are screw type also,I have looked and in residential grade there are no 20 amp back stabs I can find for 20 a feed thru rating.Now leviton does make an indusstrial receptacle that is 20 feed thru.But it is not a back stab per say it has an opening for wire but uses a set screw type of securing the wire,There is also a short guard to prevent accidental shorting while being mounted.
 

kbsparky

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

...Neither UL or the NEC say you can not run a 20 amp circuit through a 15 amp duplex...
Sure they do. That is why they are Listed for a certain value. A 15 Amp receptacle is only listed at 15 Amps. The Code is very specific about not exceeding the ratings of listed devices. 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.

Again, no one has provided me with what I would consider acceptable documentation in this matter.
 

kbsparky

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

...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.
 

apauling

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

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.

Is the perceived problem the assumption that a lesser quality of metal is used or that there is insufficient metal between the tabs to carry 20 amps? The listing implies that the duplex recpt's were tested for all single wire allowable uses, which includes 20 to 20 feed thru.

Does the metal between the recpt. tabs seem too close in size to a 20 amp fuse's metal connection?

paul
 

iwire

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

Originally posted by kbsparky:
Again, no one has provided me with what I would consider acceptable documentation in this matter.
Now I am not going to get any sleep tonight. :D

I believe UL answers questions by email, you could try that.
 

kbsparky

Senior Member
Location
Delmarva, USA
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?
Frank, that is another issue beyond the scope of this thread. You can start a new thread on that if you wish.
 
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