20 Amp outlets vs 15 Amp outlets on 20A circuit

[DIYorBust]

15 amp outlets are a little cheaper than 20 amp outlets, and I see them used much more commonly. I understand that a 15 amp outlets will pass 20 amps and can be used with 20A wiring. The question I have is can the receptacle itself pass 20amps?

Here's an example:
I plug in an extension cord that has a 15 amp plug style, and 3 outlets. Here is an link to such a cord:
https://www.amazon.com/GE-Designer-Extension-Protection-38433/dp/B073R2D51S

Suppose I plug two 10 Amp appliances into the extension cord. They run continuously, but do not trip the 20A circuit breaker. Will the 15 Amp receptacle be damaged by this, or is it ok? My intuition is the 15amp receptacles can handle 20A or they would not be permitted on a 20A breaker for this reason, but I can't find a clear answer on this. Anyone know?

Thanks!

DIY

 

[Sylvan]

All my outlets are rated 20 amps or more

On start up an ac can pull a lot of amps

You should look up the NEC before dabbling in a licensed trade

Decades ago I was a stationary engineer at 90 Church street Manhattan and took course in industrial electrical service in OU .

I no longer have the NEC code book once I became a master plumber I gave them away .

If your not sure you can call a local inspector on LI

 

[Sponsor]

 

[WorthFlorida]

I never understand why so many want to go on the cheap when it comes to electric. NEC table reads that a 15 amp "rated" receptacle can be used on a 20 amp circuit. Problem is there are real cheap receptacles and then there are good ones. Don't go with the 69 cents one sold loose, they will not last as long and will get very warm if and when the current gets near 15 amps. I always buy the Leviton "preferred" or "commercial" grade and I have used these on 20 amp circuits. When a heavy load will be drawn such as for a power tools, then I go with the 20a rated receptacles. The same quality with back wire. Extension cords is another topic. They have a maximum current rating. If it is rated at 10 amps and you are going to draw 14 amps continuously, it will get warm and may drop the voltage. Just because you plug in two cords rated at 10 amps each, and will draw 20 amps maximum between the two, doesn't mean the 15 amp receptacle will hold up.

The rule of thumb is 80%. If there is going to be a continuous load, the current shouldn't be more than 80% of the rated circuit. If you are going to draw more than 15 amps continuously on a 20 amp circuit, use 20 amp receptacle.

https://www.homedepot.com/p/Leviton...-Duplex-Outlet-Light-Almond-TBR15-T/301361167

https://www.homedepot.com/p/Leviton...ounding-Duplex-Outlet-White-TCR20-W/301361653

 

[Reach4]

15 amp outlets are a little cheaper than 20 amp outlets, and I see them used much more commonly. I understand that a 15 amp outlets will pass 20 amps and can be used with 20A wiring. The question I have is can the receptacle itself pass 20amps?

It is common, and explicitly permitted.

A 15 amp outlet will not accept a plug with this kind of pinout.

se are used on the rare appliance that draws more current. The 20 amp outlet has a pinout like this:

A 20 amp outlet will accept both NEMA 5-20P and NEMA 5-15P plugs.

A 15 amp outlet only accepts the NEMA 5-15P:

And those are the common ones.

5-15P and 5-20P plugs come in different grades, with builder grade being the cheapest.

 

[wwhitney]

My information is restricted to "preferred" grade receptacles and above. For these, my understanding is that the only difference between the 15A receptacle and the 20A receptacle in a given product line is the shape of the neutral hole in the nylon face. [This would imply that the neutral wiper is always T-shaped, but I may be wrong about that part, the neutral wiper might also be different.] The upshot is that the only reason to ever use a 20A receptacle is in the rare case you have a piece of equipment with a 20A plug.

Cheers, Wayne

 

[DIYorBust]

My information is restricted to "preferred" grade receptacles and above. For these, my understanding is that the only difference between the 15A receptacle and the 20A receptacle in a given product line is the shape of the neutral hole in the nylon face. [This would imply that the neutral wiper is always T-shaped, but I may be wrong about that part, the neutral wiper might also be different.] The upshot is that the only reason to ever use a 20A receptacle is in the rare case you have a piece of equipment with a 20A plug.

Cheers, Wayne

Wayne this is what I thought, but I can't find any documentation to prove it. Given that the NEC is conservative, I doubt that they would allow such an obvious hazard where 20A could burn up an outlet while not tripping the breaker in a code compliant setup.

Indeed I am using levitons, not looking to cheap out on the outlets. But I have never in my life used a 20A NEMA plug, and I'm not sure I'd want such a device plugged in just anywhere. Plus it'd be pretty easy to swap the outlet if I ever did need one.

Has anyone ever actually encountered a device like this? Maybe a hairdryer or space heater? Some kind of tool? Perhaps commercial or hospital equipment? It seems like most consumer items are either made to run on a 15A plug, or on a 240V circuit.

 

[wwhitney]

Wayne this is what I thought, but I can't find any documentation to prove it.

Well, my statement about internal construction is secondhand (via an Internet forum) from people who have disassembled them.

What is documented is that they are rated for 20A pass through. But that's for the wiring connections, not the wipers that connect to the plug.

Cheers Wayne

 

[WorthFlorida]

Trying to understand it, other than the neutral blades being different on the 20 amp, it could be the UL requirements might be the same. When a company is too manufacture millions of these, why not build them the same with the same UL requirements. It could be that since a 15 amp will fit a 20 amp circuit that it would be very easy for anyone to put in an underrated outlet, therefore for safety....

 

[Reach4]

Trying to understand it, other than the neutral blades being different on the 20 amp, it could be the UL requirements might be the same. When a company is too manufacture millions of these, why not build them the same with the same UL requirements. It could be that since a 15 amp will fit a 20 amp circuit that it would be very easy for anyone to put in an underrated outlet, therefore for safety....

Even the 15 amp GFCIs are rated for 20 amp pass-thru.

 

[DIYorBust]

Even the 15 amp GFCIs are rated for 20 amp pass-thru.

Right, I think Wayne said it clearly, we all agree the 15a outlets are rated for 20A passthrough, but are the wipers rated for 20A? One would hope so, but there doesn't seem to be a clear statement of this spec anywhere.

 

[Jadnashua]

Copper costs money, and since the pin orientation of a 15A receptacle won't allow a 20A device to be plugged in, why make that part heavier? To make it into a 20A receptacle, depending on the implementation, many of them have a T-shaped slot to accept either a 15A plug or a 20A one. You tend to see the dedicated 20A only when on a dedicated circuit for a specific device.

So, as I understand it, a 15A receptacle is allowed on a 20A circuit, and the screw or other contacts on it will allow 20A to be safely pasted through, bt there is no requirement for the individual receptacles to handle 20A directly, and, it's not tested with 20A there, as you literally can't plug it into a 15A receptacle.

What gets me is that a 50A receptacle like for a dryer or stove is allowed on a 40A circuit.

 

[wwhitney]

What gets me is that a 50A receptacle like for a dryer or stove is allowed on a 40A circuit.

What's wrong with that? There are no 40A receptacles, so how else are you going to put a receptacle on a 40A circuit? If you consider it "false advertising", just label the receptacle as 40A.

When a circuit has just one receptacle (not a duplex), the only requirement is that the receptacle rating match or exceed the OCPD. I'm fairly sure there are welders that come with a 50A plug but based on the duty cycle only require a 20A circuit. So you may find a 50A receptacle on a 20A circuit.

Cheers, Wayne

 

[DIYorBust]

Copper costs money, and since the pin orientation of a 15A receptacle won't allow a 20A device to be plugged in, why make that part heavier?

Yeah I don't know, would it actually save them money to use another gauge of material in different outlet wipers? If the outlet is passthrough rated for 20A, is it possible to use a wiper not rated for 20A?

 

[Jadnashua]

What's wrong with that? There are no 40A receptacles, so how else are you going to put a receptacle on a 40A circuit? If you consider it "false advertising", just label the receptacle as 40A.

When a circuit has just one receptacle (not a duplex), the only requirement is that the receptacle rating match or exceed the OCPD. I'm fairly sure there are welders that come with a 50A plug but based on the duty cycle only require a 20A circuit. So you may find a 50A receptacle on a 20A circuit.

Cheers, Wayne

With that reasoning, then why is it not also okay to install 20A receptacles on a 15A circuit? Code specifically prohibits that. The logic seems to be that by specifying a plug design that cannot be used with a higher powered device is controlled by the receptacle...that all goes out the door with your view. The idea is to protect people from themselves. While a 20A 120vac device might work for a bit on a 15A circuit, it would eventually, if used long enough, probably trip the breaker, but that's a different issue. The way the code works for that, you just cannot plug a 20A device into a 15A circuit that was installed per the code.

 

[wwhitney]

With that reasoning, then why is it not also okay to install 20A receptacles on a 15A circuit?

If a 15A circuit has only a single receptacle and no other outlets, then a 20A receptacle is allowed.

Basically the NEC treats general purpose circuits, with multiple receptacles (typically 120V 15A or 20A), differently from circuits with only a single receptacle (typically dedicated to a piece of equipment).

So yes, for general purpose circuits, the receptacle rating has to match the circuit rating, as it is understood that people will be plugging different things in. But for a circuit with only a single receptacle, that is far less likely to happen, so the rules are different.

Cheers, Wayne

 

[DIYorBust]

It seems that it is more complicated than I thought. It seems like the capacity of the outlets on a multi outlet circuit are supposed to be de-rated to 80%, so you're not actually supposed to plug a 20A appliance into a 20 amp outlet if there are two or more receptacles on the branch. But how can this be relied on? It doesn't make a ton of sense. I found this theory here:
https://www.ecmag.com/section/systems/misleading-circuit

 

[wwhitney]

If your utilization equipment needs 16A, it should have a 20A plug, and you can plug it into a multi-outlet branch circuit. If the utilization equipment needs >16A but <=20A , it should have a 20A plug, and the instructions should say to install it on an individual branch circuit.

However, this section (210.23(A)(1)) is basically unenforceable. The NEC police aren't around to regulate what a homeowner plugs into a receptacle.

Cheers, Wayne

 

[Jadnashua]

There's a general rule that continuous use of a device should derate the circuit to 80%. This is a common thing with say an EVSE used to recharge an EV. For example, a fairly typical 32A EVSE MUST be fed with at least a 40A circuit (i.e., 80% of 40A). So, say you had a 40A EVSE, you'd need at least a 50A circuit to feed it.

Note, the protection device is to protect the wiring, not necessary any device connected to it. Some devices may have internal protection, but their plug should help define an acceptable power source, assuming it was built properly.

 

[wwhitney]

That's all correct, but this is a different 80% factor, as 210.23(A)(1) is not restricted to continuous loads.

Instead 210.23(A)(1) appears to be a statement that a device plugged into a general purpose (multi-receptacle) circuit should not "hog" the whole circuit but should be restricted to 80% of the circuit rating. If you want to use more than 80% of the circuit rating, even for a non-continuous load, you are supposed to use an individual branch circuit (dedicated to one receptacle).

Cheers, Wayne

 

[DIYorBust]

So its like saying you can install a shower, and the homeowner can only turn the water 80% of the way on.