Why are lights on 15 amp circuits and receptacles on 20 amp?


It matters if there's mere overload but less than a short. 14 gauge wire cannot carry 20A safely. So why use 14 gauge? The answer is you are corralled into it by market forces: it makes for easier, faster, cheaper work. Here are the factors that come into that.

Stranded vs Solid-core. Stranded wire bends much easier, but costs 5-10% more. Solid-core is stiffer, and 12 gauge can be a real wrestling match in a small junction box.

Sheathing/grouping. Wire must be grouped and protected. Conduit is very hard to install, but easily expanded later by pulling more single wires. Non-Metallic NM (aka Romex) is 3-5 wires permanently bundled together.

Wire size, typically 14 or 12 gauge, determines ampacity. In solid wire, heavier wire is obviously stiffer. And more costly - 12 gauge NM is 50% more -- however for conduit, 12 gauge THHN is only 20% more (go figure). NM only comes in solid-core, so being multiple conductors, gets quite stiff - even moreso with 12...

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[Summary]How to Install a 20Amp Outlet on a 20Amp Circuit NEC Rules for 15Amp Receptacles on a 20Amp Circuit The NEC states that only 15Amp (with 20Amp feedthrough) and 20Amp receptacles may be installed on a 20Amp circuit. The NEC also states that only a 15A


How to Install a 20Amp Outlet on a 20Amp Circuit NEC Rules for 15Amp Receptacles on a 20Amp Circuit

The NEC states that only 15Amp (with 20Amp feedthrough) and 20Amp receptacles may be installed on a 20Amp circuit. The NEC also states that only a 15Amp rece...

15amp receptacles on 20amp cicuits

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Why 15 amp for 20 amp circuit? | Leviton Online Knowledgebase

There are many applications where you may have a 20A circuit but the actual...

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As long as there is more than one receptacle on the circuit the code specifically allows 15 amp receptacles on 20 amp circuits.

And duplex receptacles count as 2.

From the 2005 NEC.

"210.21 Outlet Devices

Outlet devices shall have an ampere rating that is not less than the load to be served and shall comply with 210.21(A) and (B).


(B) Receptacles


(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."

Now table 210.21(B)(3) will not copy and paste, but it shows

For 15 amp circuit not over 15 amp receptacle.

And for 20 amp circuit 15 or 20 amp receptacle.

This is not code, but commentary from the NEC Handbook.

"A single receptacle...

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The key concern is overloads. Both 15 and 20 amp breakers will trip
on direct shorts (if they are working properly).

There is a tradeoff.

20A circuits have a convenience factor with the ability to delivery a
considerable greater amount of power to a given situation. A typical
example today would be a home office with multiple monitors, printers,
computers and accessories in addition to whatever other routine loads
(vacuum cleaners, electric heaters, etc.) are placed on the circuit.

That extra 5A capability might just be the difference between adaquate
wiring or a long-term headache of a constantly tripping circuit

On the other hand, the subloads on a 20A circuit might (possible) pose
a safety issue. The 18 gauge lamp cord example has already been

The danger being that if the 18 g. wire is overloaded just enough for
the 18 g. wire to melt, but not enough to trip a 20A breaker. (In

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210 allows a 15 amp receptacle on a 20 amp circuit where two or more receptacles are installed on that circuit, but if you use a single receptacle on a individual 20 amp branch circuit then the receptacle must be rated 20 amps (210.21(B)(1), a single receptacle is one contact device on a single yoke, a duplex is two contact devices or two receptacles and thus allowed on a 20 amp circuit.

I agree with the others that all 15 and 20 amp receptacles have basically the same size straps which is why UL list them for a 20 amp pass through, you will also see this on GFCI receptacles.

One benefit of using a 20 amp receptacle on a 20 amp circuit is table 210.21(B)(2) allows a 16 amp load on the receptacle where a 15 amp receptacle is only allowed 12 amps, but then how is an inspector going to monitor what a person will plug in, to me codes like these should only be a informational note not part of the code as in most cases they are not enforceable because the inspector will be long...

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Do you have a question about a GFCI outlet? Free over the phone consultations are offered by the local Mesa electricians at Dolce Electric Company. Our in-office electrician in Mesa AZ will answer all of your questions. He will clarify where indoor and outdoor GFCI receptacles are required and help you determine why your device keeps tripping, will not reset or is not working. Our local Mesa AZ electricians are available from 8:00 AM until 5:00 PM today, Thursday, March 8th, 2018. Inquire today during regular business hours and get the information that you are looking for.

What is a GFCI Outlet and why are They Very Important?

GFCI electrical outlets are the receptacles (often rectangular in shape) with the two buttons on them labeled “reset” and “test”. G.F.C.I. stands for ground fault circuit interrupter but they are sometimes referred to simply as GFI’s. They work by constantly comparing the electricity being delivered on the hot side to the electricity...

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I've wired two circuits in my basement. One is for a utility area (cabinets and countertop) the other for a bathroom. Both 20 amp with 12 gauge wire.

For the bathroom (3 junction boxes) I plan to install a 20 amp GFCI but looking to use 15 amp outlets for the other two. My understanding from research is that this is acceptable because there are multiple outlets.

At the countertop area, I bought 2 20 amp receptacles and have a 15 amp duplex outlet with two USB receptacles.

I have no 20 amp devices. My question is, can I install only 15 amp receptacles on this circuit with no 20 amp receptacles at all? It appears ok to mix them but I am not sure if you could have only 15s and no 20s on the...

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Gallery of 15 Amp Receptacle On 20 Amp Circuit

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Maximum Number...

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The circuit breakers in the electrical panel in your house are safety devices. Each one is designed to disconnect power when the current passing through the circuit exceeds its rating. This prevents overheated wires, electrical power surges and fires. Electrical outlets don't draw power until you plug something in, so a 20-amp circuit should theoretically be able to handle as many outlets as you want without overloading the breaker. There are practical limits, though.

Allowable Breaker Load

The National Electrical Code doesn't limit the number of receptacles you can place on a 20-amp circuit, but you'll overload the breaker if you run appliances that draw more current than the breaker can handle. The NEC does specify that a circuit breaker shouldn't handle more than 80 percent of the load for which it is rated unless the breaker is labeled otherwise. By this standard, the total current draw on a 20-amp circuit shouldn't exceed 16 amps. This allows the breaker to...

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No limits, other then you must consider the loads (if known)

Lighting is not considered a continous load
As long as you do not expect the lighting to be on all at once I load my lighting circuit to Max capacity

If its all one room & you might have (18) 100w lights on for 8 hours then I would split them up
But I use CFL's, so not worried about overloading any of my circuits

Receptacles I always run a 20a circuit
Many vacuums take 12a these days; hair dryers, space heaters, dehumidifiers, AC's etc all use a lot of power...so I run only 20a circuits

Bathroom must have a dedicated 20a circuit that can also feed lights
Bathroom outlet can be on a shared 20a circuit with other bathrooms IF there aren't any lights being fed

I try to run circuits based on what I might use
My new additiona I am keeping number of outlets to maybe 6-8 Max & alternate outlets as you go along are on a different...

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Electrical code basics and recommended practices for kitchen renovation often seem like pointless rules cooked up in an office boardroom, as electrical code eventually does get hammered out across conference tables. Most of it, however, originates from people who work in the field: electricians, contractors, and other industry professionals.

These recommendations influence the U.S. National Fire Protection Association (NFPA).

This is the group that writes the National Electrical Code (NEC), which then is adopted in whole or part by your municipality.

So it is more than about making your local inspector happy than anything else. Far from draconian, the code actually addresses only the bare minimum. The NFPA updates the code every 3 years to meet the increasing requirements of the modern kitchen. Are you current with code?

GFCI-Protected Small Appliance Circuits

Requirement: Provide at least two 20-amp, 120-volt circuits to supply power to GFCI...

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The do-it-yourself electrician is in a little different ballpark than other DIYers. If you do your own plumbing, what's the worst that can happen? You spring a leak and maybe grandma's ashes get soaked. DIY carpentry may mean a crooked door or squeaky floor. But mess up the electrical, and lives are at stake.

That's why most municipalities don't encourage DIY electricians. If there's any doubt, they shout, hire a licensed professional. You can find local electrical pros online.

Still, homeowners can take on their own wiring, though electrical inspectors may cringe when they visit. This list sheds light on 10 common code problems that inspectors find:

1. Wrong size, A. Nowadays, lighting usually is on a 15-ampere circuit, and receptacles are on 20-amp circuits. You can't run a 15-amp line to a receptacle. There are exceptions, of course. For instance, a refrigerator may plug into a dedicated, 15-amp circuit.

2. Wrong size, B. A 15-amp circuit can use...

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Thanks for the reply. So does this mean that one can mix an match 14 and 12 guage wire on the same circuit so long as the breaker is rated for 15 amp? Intuitively that makes sense - it would just mean that the wiring for part of the circuit is over-speced.

What my thick skull still dopesn't get is why it's okay to put 15amp receptacles on a 20amp circuit, unless 15amp and 20amp receptacles are really the same in terms of the power they can handle it's just the horizontal blade that is different (maybe I just answered my own question). I'd be concerned about plugging in two 8+ amp appliances in to each plug of a receptacle, having the receptacle overheat, but the breaker not tripping.

Sorry for being dense - just like to understand what I'm doing....

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Presentation on theme: "Home Electrical Wiring Types of Receptacles and Wiring them for 120v – 15Amp/20Amp."— Presentation transcript:

1 Home Electrical Wiring Types of Receptacles and Wiring them for 120v – 15Amp/20Amp

2 Understanding the wires You have 3 wires in a home electrical system; Hot (Black wire) - dangerous one Neutral (White wire) Ground (bare copper or green wire). To make things work you need to have the hot wire and the neutral wire connected to the appliance (load). The neutral wire and the ground wire are actually one in the same. If you trace back to the breaker panel you will find that the two are connected together. The ground wire is used as a safety on loads where the enclosure is made of metal and the potential for electrical shock is present. If the hot wire shorts out some how, the ground wire which is attached to the metal will prevent you...

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Reader Question: Many over-range microwaves say they require a dedicated 20-amp branch circuit, but include a plug that can easily be plugged into a 15-amp receptacle. Is it safe to plug the microwave into a 15 amp circuit? — John

15-Amp vs. 20-Amp Receptacles

John, before we answer the question (which is a great one by the way), let’s review receptacle types. A standard 15-amp grounded receptacle is the one most of us are used to seeing throughout our house. It has two vertical slots–one slightly larger than the other–and a circular grounding slot at the bottom. A 20-amp receptacle, which is more commonly found in office buildings, looks just like the 15-amp version but has an extra horizontal slot, making the left slot look like a sideways T. (pictures available here from wikipedia)

When the microwave says it requires a dedicated 20-amp branch circuit, you would expect it to have a plug that can only plug into a 20-amp receptacle — a plug with a horizontal...

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Get one of the Home wiring books from home Depot.

There's way too much you need to know to try to give it all here.

(McPartland, one of the Authors was on the Code committee.)

20A. circuits are OK for general wiring as long as #12 Cu. wire is used.

(The "Someone" who gave you that nonsense on the light-bulbs

knows nothing and is not to be relied on for advice.)

You can combine receptacles and lights on 'general use' circuits,
but do be aware of the Code requirements for separate 'dedicated'
20A. circuits for kitchen, laundry, and bathrooms, and the requirements
for AFCI protection for outlets in bedrooms, and GFCI protection for
bathroom, basement, and exterior outlets which affect the way you run
your circuits.
Pay attention to details, (Box fill, etc.), the inspectors will, if they're
hostile to...

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General Use Circuits 2

The Numbers

Keeping in mind what I said on the previous page, here are some general rules and numbers to help you along:


500 Square Feet Rule. If you are using just the code required lighting and outlet spacing, you can generally be in good shape putting about 500 square feet on a 15 amp circuit. No more than 80%. When adding up the numbers, remember that you can only safely load a general circuit to 80%. This means only 12 amps (1440 VA) on a 15 amp circuit and 16 amps (1920 VA) on a 20 amp circuit.

The Numbers

Receptacle Outlets. It's hard to put an exact number on residential outlets, as over half of them don't get used, or whatever is plugged in is not on at the same time, that's why we have our 500 square foot rule. If you must add up your receptacles, you can use a general rule of 180 VA each.
General Lights! Most basic, ceiling mount room lights use two 60 watt light bulbs for a total of 120 watts (or...
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Hi I am Drew Fendy, master home inspector. I have been inspecting for over 24 years. Today we are going to describe how to install an electrical receptacle. One choice you need to make when you are planning is whether you are going to have a 20-amp circuit or 15-amp circuit. If it is going into a kitchen it has got to be a 20-amp circuit because you have a lot of heavy current devices there. In other locations it depends on what you are going to use it for. Anything it draws a lot of power you are going to want 20-amp for it. Usually something reproduces heat you are going to want the 20-amp for like a toaster, oven or microwave that’s what you have in your kitchen. If you are going to have an air-conditioner you would want 20-amp. If you are going to have just a radio or a lamp then the 15-amp would be more than sufficient. So look it what you are going to be using it for and then you can decide if it is a 20-amp or 15-amp that will be going for. The difference between a 15-amp...

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What dictates this? The outlets will be used to power tools while finishing and if i replace the outlet breaker but not wiring, run risk of a 30 amp fine your dryer’s is might 18 apr 2017 you…

Come along as Dave and I install a 20amp electrical outlet in Daves garage.

15-amp and 20-amp electrical outlets are installed differently. Learn how to install and wire a new electrical outlet with expert tips and advice on home improvement in this free video. Expert:…

Stanley 20-556 6-Inch FatMax Jab Saw – Drywall Saw – Amazon.com: http://amzn.to/1tv0JK4 Leviton 16342-W 20-Amp, 125-Volt, Decora Plus Duplex Receptacle, Straight Blade, Commercial Grade, Self…

The NEC states that only 15Amp (with 20Amp feedthrough) and 20Amp receptacles may be installed on a 20Amp circuit. The NEC also states that only a 15Amp receptacle may be installed on a 15Amp…

Here I’ll walk you through how many outlets...

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–Check local regulations for restrictions and permit requirements before beginning electrical work– The user of this information is responsible for following all applicable regulations and best practices when performing electrical work. If the user is unable to perform electrical work themselves, a qualified electrician should be consulted.

–Most wiring diagrams on this site include a green dot representing the integrated grounding terminal found in most metal outlet boxes. However, some older metal boxes and most plastic boxes don't have a terminal like this.
–By code, the number of conductors allowed in a box are limited depending on its size. Conductors include wires, devices like switches and receptacles, and some other metal parts. Check here to calculate the number of conductors allowed in a box before adding new wiring, etc.

This page contains wiring diagrams for a service panel breaker box and circuit breakers including: 15amp, 20amp, 30amp and 50amp, as...

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You could certainly apply those restrictions to your residential installations if you wanted, but those aren't NEC requirements.

Continue on and read 220.14 [J], Dwelling Occupancies then even 220.16 as well.

For resi, the allowance for general-purpose branch circuit receptacle loads has already been made through the general lighting load calcs done for the service and feeder calcs.

For other than dwelling units, 20A X 120V = 2400W /180VA = 13 maximum receptacle outlets on a 20A circuit. No further calcs or reductions are required.

The NEC states receptacle outlets and makes no differentiation as to the whether they are standard or GFCI receptacle outlets. See 406.3, D[3] about use of those stickers.

There is also no 80% load limitation on a branch circuit used with these receptacles.

The 80% limitation is on the receptacles themselves based on Table 210.21,B[2], which states 16A maximum load on a 20A receptacle.


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Thanks for answers. I really do appreciate it. i think i completely underestimated the task of wiring my own house.

I was also just browsing around on the site -- there is a mention of 600mm max height for washer dryer in laundry room if there is also a tub there -- my new laundry room will have a washtub -- is this spec. true in general, or only if the laundry room has a tub? Or is this spec. false for ontario. Furthermore, the post mentions that if the tub is there, all outlets have to be GFCI -- does the washing machine recepticle need to be GFCI? I don't believe i have seen a GFCI dryer recepticle, but if there is a tub in the laundry room, how do i interpret the GFCI issue?

I will be doing the mechanical room next: The house is in the country, so we will be on propane and well / septic. There will be a well pump and a pressure tank, a propane furnace, water softener and iron remover, HRV (15A), an ejector pit and a sump pump, and finally an electric water...

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I have never been shy about telling you what I don't know. And I don't know much about electrical issues. But I try to learn from others and then put that information in terms everyone can understand.

So the discussions below are my attempt to simplify what can be a very complicated system to comprehend.

Basic RV Electrical

I was thinking about what I should cover in a "Basic RV Electrical" section. Then it dawned on me that I would want it to be really, really basic.

I asked myself this question: What is the absolute minimum I need to know about my electrical system so I can run my appliances?

So let's start with the assumption that you will ALWAYS park where you can plug your rig into an electrical outlet. Then we will expand from there.

Is Your RV A 30-Amp Rig Or A 50-Amp Rig?

Every RV these days comes with a power cord meant to plug into a campground electrical pedestal like the one below.

Your RV will be either a...

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