Breaker Sizes

[Crash117]

What about hard wired loads? Such as an air hanlding unit that only drawing 2 or 3 amps. Is a 15 amp breaker responsible to protect that?

Hard wire loads like that should have a separate disconnect which is fused for the unit.

 

[Carultch]

So physically a 5 or 10 amp breaker would be different than a 15 amp breaker or higher?

Usually manufacturers group similar size breakers in categories, called frame sizes. Typical frame sizes I've seen are 60A, 100A, 200A, 300A, 400A, 600A, 800A, 1000A, and 1200A. This means 90% of the ingredients of the breaker are the same for the smaller sizes within the category, such that a 40A and 60A breaker would be mostly the same, and both be considered 60A frame sizes. The essential difference is the calibration of the trip mechanism. E.g. the thermal sensing bimetallic strip, the solenoid, the magnet, etc.

If there were a 5A or 10A breaker, it likely would have the same physical construction as a 15A breaker, with just a different trip calibration. Usually, the DIN rail breakers that would exist in 5A or 10A sizes, are built in sizes up to 30A, and all breakers in any given family, are 90% the same with just the trip mechanism being different.

 

[Carultch]

I'd say the same thing applies to us: it's not economical to place so few outlets on each circuit.

True. It's much more economical to gang-up multiple receptacles and/or light fixtures on the same circuit, and use 20A circuits, instead of just running individual 5A circuits to each light fixture.

 

[hbiss]

Someone in authority claims that each outlet or receptacle will use 1.5 amps on average. 80 percent of a 15 amp circuit is 12 amps. 12 amps divided by 1.5 amps equals 8 outlets/ receptacles. That's the golden rule.

Except for SABCs, bathroom receptacles, laundry and some other dedicated circuits, you could put the entire rest of the house on one 15A circuit if you wanted.

-Hal

 

[electrofelon]

I'm trying to help out the OP since he is hung up on grasping the answer to his questions. why criticize my basic answer to his questions?
I think wiring has everything to do with what I mentioned.

I don't see how Larry criticised you. Most of us on here are very picky about answers being 100% correct. There are some who believe the 180 VA each applies to installations not just calculations, even though the code doesn't say that. Then there are some who just use that as a good common practice rule. I personally do not find it accurate to call that a "golden rule" as I don't find it particularly common. Also just note that even if the 180va applied to installations, there would most times be no 80% derating, that is for continuous loads only.

 

[BarryO]

In other words, a load that only draws 3.6 amps (for example) would be designed to still be able to handle 15 amps?

The NEC defines several ampacity ratings for branch circuits, with the minimum being 15. A standard piece of household equipment with a NEMA 5-15P plug may get plugged into a branch circuit with a 15A or 20A overcurrent protection device. It is the equipment manufacturer's responsibility (and something UL will test for) to design their equipment to function safely on such branch circuits. Sometimes, this may involve supplementary overcurrent protection in the equipment itself; e.g., Christmas lights with fuses installed in the plug.

 

[Speedskater]

It's about receptacles. There are no common receptacles designed for 10 Amps. So just like, you can't put a 20 Amp receptacle on a 15 Amp breaker circuit, you couldn't put a 10 Amp breaker (if available) on a circuit with 15 Amp receptacles.

But with LED lighting systems, 10 Amp circuits need to be thought about.

 

[LarryFine]

In other words, a load that only draws 3.6 amps (for example) would be designed to still be able to handle 15 amps?

This reminds me of people who think using a car battery to jump-start a motorcycle will cause the bike's battery to explode. As long as you're within the designed voltage range, the line current should never exceed the load's demand. The 3.6a load's wiring should never see 15a.

 

[LarryFine]

I'm trying to help out the OP since he is hung up on grasping the answer to his questions. why criticize my basic answer to his questions?

It wasn't a criticism, but a clarification.

I think wiring has everything to do with what I mentioned.

The 180va figure is in the load calcs section.

 

[NoahsArc]

I guess the real question is "why bother going smaller", code aside?
There are some very minor use cases where it would be worth bothering. Other than the AHU example, which is a very minor inefficiency on a SFH, name one more...
15A is a good minimum, because heating elements usually run at a wattage that would snap a 10A breaker when combined with almost any other loads.

Except for SABCs, bathroom receptacles, laundry and some other dedicated circuits, you could put the entire rest of the house on one 15A circuit if you wanted.

-Hal

I've tripped breakers too often when my wife and I both wanted to run heating-type appliances at the same time. It is nice to have zones, but it adds cost. You're sizing each circuit for its maximum demand over the year, not its average, much like mini services.

Larger houses around here would need at least 2 circuits just for all-new LED lighting. Last December I had to play "balance the loads" for Christmas lighting between two circuits on a mansion because the dedicated 20A landscape lighting circuit and the 15A foyer/dining room/ power room/ hall circuit couldn't handle that added load, and I was maxing them both out just trying to get the ~20 strings balanced. We were [this] close to adding in a third circuit and outlet to the exterior. They had about two full panels, including the most random appliances, like a sauna heater, a clothing steamer, a heated drawer, and a few others I can't recall, and I was adding the EV circuit on top.

Calculated load was near 300A+, but sure outside of Christmas they probably only used 50A on an average day, excluding AC and EV.

 

[chi]

I don't see how Larry criticised you. Most of us on here are very picky about answers being 100% correct. There are some who believe the 180 VA each applies to installations not just calculations, even though the code doesn't say that. Then there are some who just use that as a good common practice rule. I personally do not find it accurate to call that a "golden rule" as I don't find it particularly common. Also just note that even if the 180va applied to installations, there would most times be no 80% derating, that is for continuous loads only.

There is nothing incorrect about what I said. Too bad you don't like the term golden rule.

 

[infinity]

Someone in authority claims that each outlet or receptacle will use 1.5 amps on average. 80 percent of a 15 amp circuit is 12 amps. 12 amps divided by 1.5 amps equals 8 outlets/ receptacles. That's the golden rule.

Are you referring to non-dwelling receptacles? The NEC would apply to nothing you've said when you have a 15 amp dwelling receptacle circuit.

 

[chi]

It wasn't a criticism, but a clarification.


The 180va figure is in the load calcs section.

Load calculations are directly related to overcurrent protection. It is called cross-referencing.

 

[chi]

Except for SABCs, bathroom receptacles, laundry and some other dedicated circuits, you could put the entire rest of the house on one 15A circuit if you wanted.

-Hal

I know that, and I never would use a 15 amp circuit for SABCs, laundry, or other dedicated circuits. That is a different situation and a different circuit from what I was speaking.
Also, I would never wire too many receptacles and outlets on a 15-amp circuit. I know one guy on this forum does not like the term golden rule but I have followed that for many years on a 15 amp circuit.
I will leave it to you guys to do your thing on this forum. I'm too old for this.

 

[electrofelon]

There is nothing incorrect about what I said. Too bad you don't like the term golden rule.

Yes there was. Even going by 180 VA per recep, you would not take 80% of that . 80% is for continuous loads and 220.14(I) receps are unlikely to be continuous loads. It's a free country and you can use whatever rule of thumb you want, but your implication that your 8 is some standardized industry thing is just not true.

 

[Jraef]

The real issue is this:
Breakers in panels are intended to be either a FEEDER, meaning there may be other branch devices downstream, or BRANCH circuit protective device (BCPD), meaning they are intended to be the last device protecting the circuit, not necessarily the load, because the load may change. So because for MOST applications the smallest branch circuit conductors allowed for field wiring is 14ga, 15A is the smallest branch breaker most people offer. (There are special circumstances where 16ga wire is allowed, hence a FEW manufacturers offer a 10A branch breaker for the panel, but the applications where those can be used are rare.)

So given that fact, when someone goes to get their NRTL (UL, ETL, CSA) listing of a DEVICE that is small enough to be used on a 15A branch circuit, the listing of that device has to take into account that the BCPD protecting it will be 15A. That means the testing it goes through to attain the NRTL listing will be done with that in mind, OR, they will have to test it with a SMALLER protective device, in which case they must either PROVIDE that device, or state in the instructions that it needs that. So for example if you are plugging in a small transformer for a doorbell, that transformer is not going to draw anywhere near15A, but when it was UL listed, it was TESTED to where by the time a 15A breaker tripped, that transformer did NOT start a fire. In reality, a LOT of small devices are designed with "sacrificial wires" inside, essentially acting as a form of fuse, to prevent that fire from happening. The device will not longer be functional of course, but that wasn't the goal; the goal was to not start a fire and not need another fuse when installing it. If a device is not listed by an NRTL, you are on your own for how you protect it and since the NEC says devices need listing, the NEC doesn't address that situation.

Now you CAN, if you so desire, as others pointed out add SMALLER rated circuit breakers, some go down to fractions of an amp. There is nothing stopping you from doing so. Those are often referred to as "Supplementary Circuit Breakers" and are even available as UL listed under UL1077. But the caveat to using UL1077 supplementary breakers is that they CANNOT be used as the branch circuit protective devices, meaning they must have another BCPD ahead of them. So if you were to use a 1A supplementary breaker on a device, that's fine, as long as it is FED by a 15A breaker as the BCPD, and the wiring is 14ga.

 

[LarryFine]

I will leave it to you guys to do your thing on this forum. I'm too old for this.

Is it really that stressful for you to have a conversation?

 

[chi]

my mistake, you do not have to worry about me, a basic electrician giving my two cents' worth any longer. I was trying to enjoy the forum and help a guy understand a problem. I am not sophisticated enough and I will never attempt to do so ever again.
You guys can play with linguistics and enforce the proper wording of all your idiosyncrasies about the field.
I admit that I do not know the NEC from cover to cover, but my strong points lie in mathematical electrical theory and hands-on electrical construction for over 35 years, both commercial, industrial, and residential.
It's too bad a few of you guys are nitpicky and egotistical. I come from a school where I learned to help someone and not put someone down over nothing. It is typical. I will consider the source. This will be my last comment on this forum.
Peace to all of you regulars, and I hope you can find something constructive to keep your mind on instead of making yourself feel all so important and knowledgeable by pointing your finger at someone over nothing. What a waste of time.

 

[Grouch1980]

It is the equipment manufacturer's responsibility (and something UL will test for) to design their equipment to function safely on such branch circuits. Sometimes, this may involve supplementary overcurrent protection in the equipment itself; e.g., Christmas lights with fuses installed in the plug.

It's up to the manufacturer to minimize spontaneous combustion of their products.

Understood. I like the christmas lights example.

 

[Grouch1980]

This reminds me of people who think using a car battery to jump-start a motorcycle will cause the bike's battery to explode.

I never thought of doing that.