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-   -   how long to trip? type NC 20A (https://www.diychatroom.com/f18/how-long-trip-type-nc-20a-74793/)

drgkjd 06-27-2010 06:11 PM

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)

Speedy Petey 06-27-2010 06:25 PM

A 20A breaker may never trip at 22A.

darren 06-27-2010 06:38 PM

It's a Federal Pacific breaker so you probably could load it up to 222A and it wouldn't trip.:laughing:

Jim Port 06-27-2010 09:25 PM

Using the trip curve for a Square D breaker loaded at 100% to 125%, the time to trip was up to several hours.

drgkjd 06-27-2010 11:31 PM

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.

Quote:

Originally Posted by Jim Port (Post 462171)
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.


drgkjd 06-27-2010 11:40 PM

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


Quote:

Originally Posted by Speedy Petey (Post 462091)
A 20A breaker may never trip at 22A.


Scuba_Dave 06-27-2010 11:44 PM

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




frenchelectrican 06-27-2010 11:53 PM

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

Jim Port 06-28-2010 04:15 AM

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.

drgkjd 06-28-2010 11:16 PM

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.

Quote:

Originally Posted by Jim Port (Post 462288)
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.


drgkjd 06-28-2010 11:18 PM

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 (Post 462241)
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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