Confused about an NEC standard
 

All the single breakers in the electrical panel in our new house are 20 amp. ALL of them. This panel is basically a sub-panel, though it is as big as the main (200 amps). It feeds primarily to bedrooms and bathrooms. I'm sure the outlets, ceiling fans, etc are rated for 15 amps. I thought every device on a 20 amp circuit had to be rated for 20 amps, but trying to read the Code it seems to say something along the lines of, "mmmm, not really." It's either ambiguous or so precise I get confused in the verbiage.
So what does the PPOT brain trust have to say about it?

The breakers should be the amp rating as the wires for each of your circuits. #12 wiring should have 20A breakers, #14 wiring should have 15A breakers, etc. Are all of your circuits fed by this panel lighting or outlets? Are you positive your outlets are 15A? For example, our kitchen and garage have 20A outlets.

They better be, Jim. How's that garage/shop coming along?

WD15, Outlets should be rated 20 amps in your situation. Here's the deal, how often are gouging to draw 20 amps out of one single outlet in that kitchen unless one circuit is feeding lots of outlets and that are all being used at the same time. I see people put those cheap 15amp outlets hooked up to 20 amp outlets all the time only because they are much cheaper and the inspector never checks them

Seems to me that if the breaker is rated higher than the device then the circuit isn't really protected. But I'm not an electrician.

you can put 15amp outlets on a 20amp circuit, just not the other way around.
i prefer the overprotection,. not an electrician either.
just because you have 15amp outlets on a 20amp service does not mean you still cant trip a 20amp brkr.

as jim said the breaker protects the WIRES.

as gogar said, you protect the smallest ga wire.

i ran a dedicated service to my music room for the band. i ran 10g to the first box, then 12g to all outlets and put in a 20a brkr and 20amp outlets. the service split down 2 walls where the 10g tied in.

Exactly - the device (switch/outlet) or the wire.

Really good, Jeff. I got lazy over the holidays, and I still need to install my ceiling lights. I also need some wall organizers. Then it'll be done.

My son is selling his house and had the buyer's home inspector point out that his subpanel had a breaker that was too large for the wiring it had connected to it. Sure enough, the wiring was correct for the load it was carrying but the breaker should have had a smaller amperage rating. It had probably been like that since the place was built. :rolleyes:

Easy fix for him. Did he buy another place nearby. That's a great neighborhood

It's OK. Common practice.

This is from NEC code:
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dad, that's only for receptacles. Wiring will need to be at least #12 is the breaker is rated at 20A. So, it's a system...breaker, wiring, and receptacles.

Thanks for the input. I'm not going to worry about it. The installing electrician's sticker is on the box. I don't think he'd be advertising if he'd screwed the job up this badly. Wire ARE 12 ga. so they are not an issue. I was concerned about overheating a 15 amp receptacle by plugging in multiple devices.

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That's right. Breakers match branch wire.

You covered that in the first post. The posts on receptacles were unclear, so I clipped the table from the code.

Not really germane, but Just for info, I'm pretty sure that

Any device designed to fit into a 15A receptacle must pull less than 15A. A device designed to pull more than 15A has a perpendicular prong. That's why "20A" receptacles have the combo parallel/perpendicular socket.



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The issue is if an electronic device with a 15A plug has an internal failure (short) and draws MORE than 15A. The purpose of the breaker is to trip, and a 20A breaker won't trip until it senses 20A of current. So the 15A outlet, or the 14AWG wire (normal use on a 15A circuit) fails and causes overheating which leads to a fire.

Loads only use what they are designed for , 1500 watts divided by 120 volts equals 12.5 amps. On a 15 amp breaker , this is fine. On a 20 amp breaker this is fine. You will not be able to plug into a 30 amp circuit or higher due to plug configuration. As previously stated , the breakers protect the conductors. you can have 12 receptacles to a circuit. you can plug 24 appliances into this circuit but it will throw the breaker instantly when you turn them on, thus protecting the conductors and building they are in. Breakers are rated for 10000 amps symmetrically and work best when the rise of amperage is FAST. Adding more grounds or a heavier ground to a service only slows down the rise of a fault because the fault current has more paths to travel thus limiting the fault current to rise symmetrically. all services are protected by number 6 copper now so in a large fault condition, it burns through and allows the fault current to travel on the neutral back to the distribution cutout or main , depending on where the fault is. On a side note, I have often wondered about the cold flow properties of aluminum when used in cases of porsche motors, but that is another topic entirely. hope this helped.
Dan.

This is true in theory only. Some federal breakers will need up to three times the rated amperage or more before they throw the circuit. Like in many things , you get what you pay for. Square D or siemens and sleep well at night. Dan.

Guys, you are overthinking this. 12 wire, 20 amp breakers, 15A receptacle ok as long as it isn't the a single dedicated 20A feed (like for a heater or pump)

"A single receptacle installed on an individual branch circuit must have an ampere
rating not less than that of the branch circuit. For example, a single receptacle on a 20- ampere individual branch circuit must be rated at 20 amperes; however, two or more 15-ampere receptacles or duplex receptacles are permitted on a 20-ampere general purpose branch circuit. .......

15 amp duplex receptacles are rated at 20 amps pass through in the UL listings. And each 1/2 of the duplex is rated at 15 amps. So they can handle a 15 and 5 or 10 and 10 amp loads for example."

The standard 15A GFCI receptacles are rated for 20 amp feed thru. It's the plug configuration, not the device. As gogar points out, 2 vertical prongs are 15a plugs.

That is why kitchens & dining rooms are 12 gauge, 20 amp breaker, with the common 15a receptacles.

It's common to use 14 gauge 15 amp for lighting other general outlets.

dad911 ^^^^ is TOTALLY CORRECT (Elec inspector here btw)

ALso a note regarding home inspectors finding oversized breakers at inspection. Take note of typically they find breakers "oversized to wiresize" on A/C units. The NEC specifically notes exception for wire size vs breaker on these. Go to the name plate of the device for minimum wire size/maximum breaker.