6/3 NM cable

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nizak

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Correct me if I'm wrong. 6/3 NM cable can be protected by a 60A circuit breaker.I am being told that 50A is max o/c protection. My application is a sub feed to an attached garage, not an electric range where the power outlet is rated 50A. I am going by 240.4(b)(2). Thanks.
 
Known load at this time is 25-30A. Could you cite the article that pertains to the calculated load determining this breaker size. I was only going by 240.4(b) (1) (2) (3). Thank You.
 
Most folks feel the baisc wording of 240.4(B) covers that.
240.4 Protection of Conductors. Conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.15, unless otherwise permitted or required in 240.4(A) through (G).
 
If you satisfy the next size up rule and not exceed the ampacity of the conductor then you can use a 60 amp OCPD with a 55 amp conductor. You would need to know that the maximum load was 55 amps or less.

240.4(B) Overcurrent Devices Rated 800 Amperes or Less.
The next higher standard overcurrent device rating (above
the ampacity of the conductors being protected) shall be
permitted to be used, provided all of the following condi-
tions are met:
(1) The conductors being protected are not part of a branch
circuit supplying more than one receptacle for cord-
and-plug-connected portable loads.
(2) The ampacity of the conductors does not correspond
with the standard ampere rating of a fuse or a circuit
breaker without overload trip adjustments above its rat-
ing (but that shall be permitted to have other trip or
rating adjustments).
(3) The next higher standard rating selected does not ex-
ceed 800 amperes.
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This a common issue with the application of 240.4(B). That section does not change the ampacity of the conductor, it just allows us to use an OCPD with a rating higher than the conductor ampacity. The conductor must have an ampacity equal to or greater than the calculated load.
 
There are 1000's of apartments in my area that have Zinsco service equipment with 55 amp breakers protecting #6 feeders. I have not run across any other manufactures that utilized 55 amp breakers. Does anyone know if the next standard size was permitted back in the 60's and 70's?
 
55 or 60at my be be picky when you have breakers calibrated at 40degC installed in a 25degC ambient or less environment with protecting cable run through what ever ambient temperatures, I always have found it to be amazing that we can even protect the cable . Taking a look at the breaker TC trip curve will surprise some.
 
With a Zinsco breaker I don't think it makes any difference how it is marked :D
 
augie47 said:
With a Zinsco breaker I don't think it makes any difference how it is marked :D
Click to expand...

It seems that the Zinsco Bolt-Ons are able to do their intended job many years after they were installed. Plug-in type if given the only choices of Zinsco or FPE, I'll take FPE.:D Those choices are like being give the choice of a dog turd or cat turd sandwich though, thank goodness they are obsolete but have seen a few pallets of unused Challenger branded FPE panels on a local online auction, if they had gone for $5 might have got em for the scrap value, but would have liked to see the buyers face when they priced out breakers....:lol:
 
norcal said:
It seems that the Zinsco Bolt-Ons are able to do their intended job many years after they were installed. Plug-in type if given the only choices of Zinsco or FPE, I'll take FPE.:D Those choices are like being give the choice of a dog turd or cat turd sandwich though, thank goodness they are obsolete but have seen a few pallets of unused Challenger branded FPE panels on a local online auction, if they had gone for $5 might have got em for the scrap value, but would have liked to see the buyers face when they priced out breakers....:lol:
Click to expand...

Was Challenger part of FPE? I have only seen a few Challenger panels or breakers & never got any background info on them.
 
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