Breaker Sizes

[Grouch1980]

Just a general, basic question. How come the smallest standard size for circuit breakers, based on the NEC (the 2017 version, Table 240.6(A)), is 15 amps? Some loads, for example, only draw several amps... 2 amps, 3.6 amps, 4 amps, etc. How come there aren't 5 or 10 amp circuit breakers, and it only starts at 15 amp breakers?

If a load is only drawing 3 amps, how does a 15 amp circuit breaker protect it, if the breaker is sized so much larger than what the load draws?

 

[chi]

The circuit breaker is rated for the conductor size, not the draw. You can not use any AWG wire size smaller than 14 AWG which can handle 15 The golden rule is to have only 8 outlets/receptacles which is an 80 percent general load for that wire size.

 

[infinity]

If a load is only drawing 3 amps, how does a 15 amp circuit breaker protect it, if the breaker is sized so much larger than what the load draws?

The device should be designed so that the 15 amp OCPD does protect it.

 

[infinity]

The golden rule is to have only 8 outlets/receptacles which is an 80 percent general load for that wire size.

Care to expand on the golden rule?

 

[Grouch1980]

The device should be designed so that the 15 amp OCPD does protect it.

but why would manufacturers stop at 15 amps? why not make 5 or 10 amp breakers as a standard as well?

 

[Carultch]

but why would manufacturers stop at 15 amps? why not make 5 or 10 amp breakers as a standard as well?

Some do, you just don't see them in a form that can be connected inside a standard panelboard. It's mostly a matter of economics of manufacturing, that drives manufacturers to avoid making these smaller sizes. There just isn't enough customer demand to justify the return on investment. 5A and 10A receptacles don't exist either, and receptacles in general need to be installed on a breaker at least as large as the receptacle.

You usually find smaller amp trip settings available in DIN-rail breakers, rather than in breakers for panelboards and load centers. Usually, this is for monitoring and controls, rather than for circuits for general power. This would be for purposes of protecting circuits on circuit boards, that need single digit amp protection, and would usually be part of an assembled control cabinet.

 

[Grouch1980]

Some do, you just don't see them in a form that can be connected inside a standard panelboard.

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

 

[infinity]

Square D has made 10 amp QO breakers for decades but a typcial branch circuit had a minimum size of 15 amps.

 

[Grouch1980]

The device should be designed so that the 15 amp OCPD does protect it.

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

 

[infinity]

In other words, the load would be designed to still be able to handle 15 amps?

Whatever the load is it should be designed to operate on a standard 15 amp circuit. An electric clock might draw 10 watts but it is still designed to operate on a 15 amp circuit.

 

[LarryFine]

If a load is only drawing 3 amps, how does a 15 amp circuit breaker protect it, if the breaker is sized so much larger than what the load draws?

Generally, a breaker is not responsible for protecting plugged-in loads.

Also, we can hard-wire small-gauge fixture wires on 20a circuits.

 

[LarryFine]

It's mostly a matter of economics of manufacturing, that drives manufacturers to avoid making these smaller sizes.

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

 

[LarryFine]

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

No, but you would need more of them for a given service size.

 

[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?

That's why you rarely see 120v cords smaller than 18ga.

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

 

[Grouch1980]

Generally, a breaker is not responsible for protecting plugged-in loads.

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?

 

[chi]

Care to expand on the golden rule?

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.

 

[LarryFine]

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?

No, the HVAC manufacturer knows what size breakers are available, and print their instructions accordingly.

 

[chi]

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?

yes. you are hung up on overcurrent devices compared to what amperage a load is.
The circuit breaker or fuse protects the conductors from overheating. If you plug 4 blow dryers into the same circuit, it is going to draw over 15 amps and the breaker will switch off.
It does not matter if you have a little night light on.
although your electric company charges you for every watt-hour of the smallest measure.

 

[LarryFine]

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.

That 180va figure for general-use receptacles applies to load calcs, not necessarily actual wiring.

 

[chi]

That 180va figure for general-use receptacles applies to load calcs, not necessarily actual wiring.

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.