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Old 06-27-2010, 05:11 PM   #1
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how long to trip? type NC 20A


does anyone know how quickly (or slowly) a 20 amp FPE type NC breaker will trip when loaded to 22 AMP heating load??

i guess the right answer will be to find the "trip curve" (or characteristics) of this breaker but i could not find anything on the web

i had a kitchen circuit loaded at 22 amp (resistive) (of course, unintentionally) for about 10 minutes, the breaker did not trip. is this normal?

add: i used an amp meter to measure the current draw for each of the 2 appliances that were plugged in in steady-state; the actual total was 22.1

(for those who dislike FPE , telling me to change the panel at this point will not help-- that may come later)


Last edited by drgkjd; 06-27-2010 at 05:19 PM. Reason: added
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Old 06-27-2010, 05:25 PM   #2
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how long to trip? type NC 20A


A 20A breaker may never trip at 22A.

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Old 06-27-2010, 05:38 PM   #3
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how long to trip? type NC 20A


It's a Federal Pacific breaker so you probably could load it up to 222A and it wouldn't trip.
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Old 06-27-2010, 08:25 PM   #4
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how long to trip? type NC 20A


Using the trip curve for a Square D breaker loaded at 100% to 125%, the time to trip was up to several hours.
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Last edited by Jim Port; 06-28-2010 at 03:13 AM. Reason: clarity
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Old 06-27-2010, 10:31 PM   #5
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how long to trip? type NC 20A


thanks....this should not be much different than i would guess. so it seems that 10% over-current can be handled easily for 10 mins and would not cause the breaker to trip in that short a time.

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Using the trip curve for a Square D breaker loaded at 22 amps the time to trip was several hours. It might have even been more than that IIRC.
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Old 06-27-2010, 10:40 PM   #6
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how long to trip? type NC 20A


hmmmm...interesting....now i got to dig up a comparable trip curve and understand what is the usual overload for quick trip--- other than of course a complete short.

thanks


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A 20A breaker may never trip at 22A.
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Old 06-27-2010, 10:44 PM   #7
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how long to trip? type NC 20A


I loaded up a bunch of C-9 Christmas light strings on a 20a circuit
I think I had 15-16 straings on the circuit
Usually they take 175w each....so at least 1625w on the circuit
I went inside...sat down & started calc'ing the load on the circuit
Realized I had too much....looked out & they were off, breaker had kicked off...maybe 15 minutes Max
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Old 06-27-2010, 10:53 PM   #8
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how long to trip? type NC 20A


The trip setting will affect by tempture as well like what Pete say 20 amp breaker may not trip at 22 A which I have ran into from time to time and ditto with European verison the same olé story.

but if the breaker box is in basement which I know typically more cooler than on first floor or on very warm spot it may not trip very fast with mild overload at all.

Merci,
Marc
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Old 06-28-2010, 03:15 AM   #9
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how long to trip? type NC 20A


Here is a trip curve for the 15 amp.

http://static.schneider-electric.us/...kers/730-2.pdf

As you can see it can hold 100-125% load for a long time.
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Old 06-28-2010, 10:16 PM   #10
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how long to trip? type NC 20A


thanks for posting the curve. i am pretty sure the fpe is very similar and at 10% overload it my not trip for several 1000s of second and unlikely in 10 min.

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Originally Posted by Jim Port View Post
Here is a trip curve for the 15 amp.

http://static.schneider-electric.us/...kers/730-2.pdf

As you can see it can hold 100-125% load for a long time.
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Old 06-28-2010, 10:18 PM   #11
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how long to trip? type NC 20A


yes, the panel is in the basement....and as i see on the trip curve posted by jim, 10 min is too short for a 10% overload, specially in the cool basement (about 68deg there).

thanks

Quote:
Originally Posted by frenchelectrican View Post
The trip setting will affect by tempture as well like what Pete say 20 amp breaker may not trip at 22 A which I have ran into from time to time and ditto with European verison the same olé story.

but if the breaker box is in basement which I know typically more cooler than on first floor or on very warm spot it may not trip very fast with mild overload at all.

Merci,
Marc

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