AFCI :how to wire

[Dennis Alwon]

Don, this is the section that was quoted. He said he was at the big meeting in California and the cmp stated this will be passed. So how do you read this...

(2) A listed outlet branch circuit type arc-fault circuit interrupter installed at the first outlet on the branch circuit where all of the following conditions are met:
a. The branch circuit over current protection device shall be a listed circuit breaker having an instantaneous trip not exceeding 300 amperes.
b. The branch circuit wiring shall be continuous from the branch circuit overcurrent device to the outlet branch circuit arc-fault circuit interrupter.
c. The maximum length of the branch circuit wiring from the branch circuit overcurrent device to the first outlet shall not exceed 15.2 m (50 ft) for a 14 AWG or 21.3 m (70 ft) for a 12 AWG conductor.
d. The first outlet box in the branch circuit shall be identified.

 

[don_resqcapt19]

Dennis,
That was in what I had posted and I read right past it.

I guess the question is the if there are OCPDs with an instantaneous trip of 300 amps or less.

 

[Dennis Alwon]

Dennis,
That was in what I had posted and I read right past it.

I guess the question is the if there are OCPDs with an instantaneous trip of 300 amps or less.

LOL so did I................So what is the instantaneous trip of a standard 15 amp breaker

 

[al hildenbrand]

So what is the instantaneous trip of a standard 15 amp breaker

Looking at the time-current curve for the standard Square D 15 amp breaker, HOM or QO, the breaker is clearing in one cycle when the current hits 300 Amps. Any increase in current beyond 300 Amps does not improve the response time.

The graph is here.

 

[Dennis Alwon]

Looking at the time-current curve for the standard Square D 15 amp breaker, HOM or QO, the breaker is clearing in one cycle when the current hits 300 Amps. Any increase in current beyond 300 Amps does not improve the response time.

The graph is here.

But isn't it doing the same at 700 amps? I am still unclear if this breaker would qualify for the requirements of the new section

 

[al hildenbrand]

But isn't it doing the same at 700 amps?

an instantaneous trip not exceeding 300 amperes.

While I take the language to mean the instantaneous response is not requiring a minimum current greater than 300 Amps, I think the specific language used in the quote you and Don posted is confusing.

It could be interpreted that the breaker CAN'T have an instanteous response at fault current levels exceeding 300 Amps.

 

[Dennis Alwon]

While I take the language to mean the instantaneous response is not requiring a minimum current greater than 300 Amps, I think the specific language used in the quote you and Don posted is confusing.

It could be interpreted that the breaker CAN'T have an instanteous response at fault current levels exceeding 300 Amps.

I read it as not exceeding 300 amps but who knows

 

[al hildenbrand]

Maybe it should say: "an instantaneous trip threshhold not exceeding 300 Amps."

 

[don_resqcapt19]

Looking at the time-current curve for the standard Square D 15 amp breaker, HOM or QO, the breaker is clearing in one cycle when the current hits 300 Amps. Any increase in current beyond 300 Amps does not improve the response time.

The graph is here.

I don't see a one cycle trip as being an instantaneous trip.

 

[al hildenbrand]

I don't see a one cycle trip as being an instantaneous trip.

The time-current response curve shows the clearing of the fault in one cycle, not the tripping of the mechanism in one cycle.

There is no delay introduced, the mechanism is sensing the overload and reducing the output current to zero, as fast as practicable. (Which is the second part of the definition of instantaneous trip {as applied to Circuit Breakers} that is in the IEEE Authoritive Dictionary)

The graph shows that delay is introduced at a changing rate below 300 Amps and the closer the fault current approaches the breaker full load current rating.

 

[Dennis Alwon]

Here was Ge response-- not very definitive

?One of the technology people in Plainville sent me a response that they did not think the final version of the new code would be a problem meeting at this point in time. Since the code has not been released, the final wording has not yet been determined.?

 

[al hildenbrand]

Here was Ge response-- not very definitive

What was the question that GE responded to?:?

 

[Dennis Alwon]

What was the question that GE responded to?:?

Whether or not the breakers would meet the requirement of the 2014 code-- specifically this

The branch circuit over current protection device shall be a listed circuit breaker having an instantaneous trip not exceeding 300 amperes.

 

[al hildenbrand]

Whether or not the breakers would meet the requirement of the 2014 code-- specifically this

You can see GE's 20 A single pole breaker time-current curve by clicking here . To my eye it looks like the breaker doesn't get to instantaneous until around 500 Amps. I'd say they've got some work to do, or political clout to exercise.