15A Receptacles On 20A Circuits

[bphgravity]

This discussion came up during a chat session last night on the ECN Forum. I thought I should post this issue to get this Forums opinion.

The NEC requires the small appliance, laundry, and bathroom circuits to be 20A rated citcuits. The code also allows 15A rated devices on 20A branch circuits as long as the load on any one receptacle does not exceed 80%. Here's the question.

Many appliances, like the example of a 1875-Watt hairdryer, have loads that exceed the 12A allowance of a 15A receptacle that will commonly be found on the 20A bathroom receptacles. NFPA and NEMA sleep in the same bed and must be aware of this issue. The cords on the appliance are only 15A rated cords but the are being used on 12A limited devices.

So, it is my opinion that once a 15A device is installed on a 20A rated circuit, you have effectively reduced that citrcuits capacity to a 15A rated circuit and you would then be in violation of the 210.11(C) requirements.

I know in many cases, the installer has no control of what loads and how much load will be used by the user. But in this case, the problem could easily be avoided by simply requiring and installing 20A rated receptacles on 20A rated circuits. This way, a greater than 12A rated load would not be a problem and the entire 16A allowance of a 20A rated circuit could be used.

Any thoughts?

 

[jim dungar]

Re: 15A Receptacles On 20A Circuits

Your argument makes sense except it seems to be partially based on misplaced concern.

1. 15A circuits are only limited to 12A for continuous loading. There is nothing wrong with drawing 15A of non-continuous load. Sure someone might leave an appliance plugged in and turned on, but the internal thermal cutout or a thermostat will keep it from being on continuously.

2. We treat the marketing hype of appliances like is was actual nameplate information. I don't think I have seen a hair dryer that did not base their wattage at less than 125V (1875W @ 125V = 15A = 8.3 ohms => 1728W @ 120V = 14.4A). Likewise, my Craftsman garage door opener is 1/2HP 6A, so could I correctly infer that my Craftsman 8 gal Wet-Vac with "4HP max developed" will draw 48A?

 

[bphgravity]

Re: 15A Receptacles On 20A Circuits

1. 210.21(B)(2) says nothing about continuous loading ?

2. 14.4 still exceeds 12A as permitted for one receptacle load. So even with the tricky 1875-Watts at 125V, the load still exceeds that which is permimitted per Table 210.21(B)(2).

 

[charlie b]

Re: 15A Receptacles On 20A Circuits

Let me speak as an engineer who might get involved in the design of a project that might have this issue arise. My take is that my job ends at the receptacle. I am willing to accept a design that uses two or more 15 amp receptacles on a 20 amp branch circuit. I don?t agree that this would create a violation. But as you say, neither you nor I can control what the owner will plug into the receptacle.

My problem with the issue is that 210.21(B)(2) is an instruction to the homeowner, not to the designer, the electrician, or the inspector. It tells the homeowner what can and cannot be plugged into a receptacle. But the scope of NEC itself, as defined in 80.1, does not include the homeowner. So I submit for your consideration the notion that article 210.21(B)(2) should be deleted, or at least reworded such that it is no longer directed to the homeowner.

 

[luke warmwater]

Re: 15A Receptacles On 20A Circuits

Here's some test results:

Voltage present = 122.9

Tester = Amprobe ACD-10ultra

P&S 15a GFCI receptacle
20a branch circut

All (3) of the following hair dryers have 16ga cord and 15a cord cap:

IGIA Ion Aire
nameplate = 800w @ 125v
Peak start up = 6.6a
Hi Heat = 5.9a
Low Heat = 3.5a

Vidal Sassoon VS-526
nameplate = 1875w @ 125v
Peak start up = 12.7a
Hi Heat = 12.4a
Low Heat = 3.4a

Vidal Sassoon Ionizer
nameplate = 1875w @ 125v
Peak start up = 14.4
Hi Heat = 12.4
Low Heat = 3.2

Note:
All were left running for 5 min.(attended)
Branch circut wiring was not warm nor the receptacle or cords or cord caps.

So, why do the manufacturers not have to install 20a cord caps with the logic presented?

 

[bphgravity]

Re: 15A Receptacles On 20A Circuits

Originally posted by luke warmwater:
...So, why do the manufacturers not have to install 20a cord caps with the logic presented?

I don't think anyone is making that suggestion here. What the problem is, two of the hairdryers exceed 12A, the allowable load on a 15A receptacle. If bathroom circuits are required to be 20A circuits, I feel they should be able to be loaded to 20A or anyone receptacle to 16A. I tend to agree with Charlie's last statment

[ June 19, 2004, 04:23 PM: Message edited by: bphgravity ]

 

[tom baker]

Re: 15A Receptacles On 20A Circuits

Luke this has come up before. UL can list appliances designed to be used at 100% of nameplate at 125 V. But I agree with you, its a contradiction to our 80% circuit load that we normally use.

 

[bill addiss]

Re: 15A Receptacles On 20A Circuits

So, why do the manufacturers not have to install 20a cord caps with the logic presented?

I've got the same question.

There's a few changes that have been made in recent years that seem to recognize that problems might exist with today's Loads and yesterday's wiring.

One is the 20A Circuit requirement for the Bathroom Receptacle. I can only guess this is required because of today's powerful hairdryers.

The second change I'm thinking of has to do with the back-stab receptacles now being manufactured to not accept #12 ga. wire. I'm guessing again here, but I would bet the reason behind the change has something to do with limiting the load on back-stab connections (not on 20A circuits).

These two changes only help the situation if the 1875w Hairdryer is used in the Bathroom of a new House. Fact is though the they get plugged in other places too which are on 15A circuits. And, there's no help for an older Home. I think anyone that does Residential Service work has seen Hairdryers heat up connections (some close to causing fires) and cause open circuits.

Putting a 20A plug on a 1875w Hairdryer would mean that they are only used on 20A circuits, and they would not have back-stab connections.

Bill

 

[iwire]

Re: 15A Receptacles On 20A Circuits

It seems the code has a few areas where a code compliant installation will likely be used in a way that violates the NEC.

406.3(D)(3)(b) and 406.3(D)(3)(c) allow the installation of grounding outlets where no grounding means exists.

But...

250.114 prohibits using that outlet for utilization equipment that needs to be grounded. :roll:

 

[roger]

Re: 15A Receptacles On 20A Circuits

As Bill points out, these hair dryers can be used on any circuit in the house, and infact my wife uses hers (although not a 1875 watt model) in front of the bedroom dresser more than she uses it in the bathroom.

The problem with this is, let's say they are redesinged with 20 amp cord caps and someone recieves one as a gift, the happy person will simply run to the H.I. store and buy a 20 amp receptacle to replace the one they want to utilize for using the hair dryer.

Roger

 

[iwire]

Re: 15A Receptacles On 20A Circuits

the happy person will simply run to the H.I. store and buy a 20 amp receptacle to replace the one they want

Or just grab a pair of pliers and give the offending plug prong a 90 degree twist.

Not that I have ever seen that done....

[ June 20, 2004, 01:22 PM: Message edited by: iwire ]

 

[bphgravity]

Re: 15A Receptacles On 20A Circuits

I was kind-of wondering the same thing as Roger. My concern is that a homeowner would then utilize a 20A to 15A adapter plug. I see these all the time, especially where no grounding pin is provided on old 2 wire systems.

My initial concern was more in line with the fact the code requirement in 210.21 is nearly impossible to determine. The very nature of cord-and-plug connected equipment is for use in various locations and flexible portability.

I personally wouldn't like to see the NEC get involved with mandating manufacturer's standards and specifications. I just don't understand why a 15A receptacle can be used up to 15A or why a 20A receptacle can't be used for all 20A.

210.21 and 210.23 needs revision in my opinion.

 

[bill addiss]

Re: 15A Receptacles On 20A Circuits

the happy person will simply run to the H.I. store and buy a 20 amp receptacle to replace the one they want to utilize for using the hair dryer.

This may be true, but then it is a case of some unknowing/unqualified person making modifications to their Electrical system. IMO it's a weak argument. Things like that will always go on, but not everyone would do that. Many people would just not buy that model if they didn't have an outlet to plug it into, they would stick with the lower wattage models that they could use anywhere.

Bryan,

They make an adapter that would allow you to use a 20A plug in a 15A receptacle? That doesn't sound like something that would get UL approval.

 

[bphgravity]

Re: 15A Receptacles On 20A Circuits

Originally posted by bill addiss:

They make an adapter that would allow you to use a 20A plug in a 15A receptacle? That doesn't sound like something that would get UL approval.

I don't know if one of these actually exists, but I do know that there are several adapters available for RV's that convert from 30A to 15A. This is the same premise.

Here is a related response that I found on OSHA's website:

There would be several problems with using an adapter on a tool that draws 15-ampere. First, under ?1926.403(a), all adapters/plugs must be approved by a Nationally Recognized Testing Laboratory (NRTL). We are not aware of any 20 ampere to 15 ampere adapters approved by a NRTL.

Second, your question raises a problem that goes beyond whether you could obtain an approved adapter. The more fundamental problem is that, in the United States, a tool rated at 15-ampere would overload most circuits equipped with 15-ampere receptacles -- so use of such a tool on those circuits would violate ?1926.404(b)(2). The only time a 15-ampere tool could be used on a 15-ampere receptacle would be if there was only one receptacle on the circuit, and if 15-ampere was the maximum load that could be imposed by the tool. Since most tools draw above their rated load at start-up, a tool rated at 15-ampere could even overload a circuit with only one 15 ampere receptacle.

If more than one 15 ampere receptacle is on the circuit, the maximum allowable load on the receptacle would be 12 ampere. Branch circuits used on construction sites supplying a single receptacle are rarely used. Since other receptacles on the circuit would be available for use by employees using other tools, the use of a 15-ampere tool would likely overload the circuit. Even a circuit with only two receptacles might be overloaded at some point if a tool of more than 12 ampere were permitted to be used because of the power required to start the tool.

In short, since your drill draws 15-ampere, the OSHA standard would require that it be used on a circuit with a capacity over 15-ampere. In the United States, this would mean using a circuit with a minimum capacity of 20 ampere.

 

[jim dungar]

Re: 15A Receptacles On 20A Circuits

Just started to re-read 210.11, 210.21(B), 210.23 and 210.24.

Now I'm glad I don't do residential.

210.21(B)(2) prohibits an electrician (actually anyone pulling an electrical permit) from installing a cord and plug connected load in excess of 12A into any 15A receptacle. But the inspector can not red tag installations based on what might be a future situation.

At this time the only feel good solution I see, is to use 20A receptacles in bathrooms. These 20A devices (NEMA 5-20R) do not exclude the
use of 15A plugs (NEMA 5-15P), so the homeowner will not need to modify any NRTL listed equipment.

 

[charlie]

Re: 15A Receptacles On 20A Circuits

The following question was asked at an Indiana Chapter of the IAEI meeting and this was my answer. This was answered with the help of UL.

66. Does the NEC permit the installation of a 15-ampere rated duplex receptacle on a 20-ampere separate circuit for a microwave oven with a nameplate rating of 13 amperes? The microwave oven is factory equipped with a 15-ampere cord cap.

The above microwave meets the requirements of the Indiana Electrical Code since it is a listed appliance. I would run a 20 ampere small appliance branch circuit, install a single 15 ampere duplex receptacle, and wish it well. UL has listed this appliance for use on a 15 ampere circuit since is will be used in a non-continuous manner. The cord, plug, receptacle, etc. has been listed for a full 15 amperes of non-continuous use. Therefore, this is not a hazard. This same line of reasoning is used for the high wattage hair dryers.

 

[luke warmwater]

Re: 15A Receptacles On 20A Circuits

Charlie,

I don't know if it is my system, but I couldn't get your above link to work.

But, I agree with your above statement, and as for my rough tests, I do not see the harm in plugging these dryers into the 15a receptacles.

Bryan,
I was not availible for the Friday Night Chat,
What was the average opinion at ECN?

 

[hurk27]

Re: 15A Receptacles On 20A Circuits

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[a.wayne3@verizon.net]

Re: 15A Receptacles On 20A Circuits

Originally posted by jim dungar:
Just started to re-read 210.11, 210.21(B), 210.23 and 210.24.

Now I'm glad I don't do residential.

210.21(B)(2) prohibits an electrician (actually anyone pulling an electrical permit) from installing a cord and plug connected load in excess of 12A into any 15A receptacle. But the inspector can not red tag installations based on what might be a future situation.

At this time the only feel good solution I see, is to use 20A receptacles in bathrooms. These 20A devices (NEMA 5-20R) do not exclude the
use of 15A plugs (NEMA 5-15P), so the homeowner will not need to modify any NRTL listed equipment.

 

[a.wayne3@verizon.net]

Re: 15A Receptacles On 20A Circuits

I have always used the thought that if there is a dedicated circuit that the receptacle must be rated for that circuits ampacity.IE: single point of attachment #12 must have a single receptacle rated at 20 amps.Branch off to other receptacles then no longer dedicated and 15 amp receptacles are allowed.To Jim Dungar I know where you are coming from.Residential codes have taken so many twists and turns over the years and still are in gray areas.it seems what are the rules TODAY.Look at 210.52 A 2,what constitues a simular area,A hall only requires 1 receptacle for more than 10 ft. of length but this article wants any wall in a dwelling unit more than 2 ft. to have a receptacle.The wording simular area has given the AHJ cart blanche to decide what is a simular area.
Lets say there is 36 in of wall as you enter a kitchen then you have a fridge and a sub zero side by side then counter top with a receptacle within 24 ins of the sub zero.Tagged!!!6 ft.rule not met and 2 ft. rule is there.We do mostly residential work and this has come to bear time and time again.Common scense has been taken out of the picture.We did 2,000 homes last year and in these have added probably 10 receptacles in each to meet this requirement.Do the math?In tract homes the profit is low,factor in these requirments and the profit goes out the window.As an area supervisor I deal with this daily.It has become so frustrating to say the least. :roll: OK there is a wall in a kitchen that is 36 ins. but where is a recp needed in code yes but in real life no.IMHO kitchens and hallways need to be take out of this article JMHO have a great day,Allen