ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals

Topic Options
Rate This Topic
#65388 - 05/01/06 09:08 PM Circuit Breakers
96mystic Offline
Junior Member
Registered: 05/01/06
Posts: 1
Loc: Gresham, Oregon, USA
When sizing a circuit breaker, is it fair to say: multiply the calculated amperage by 1.25 and, if necessary, round up?
Thanks in advance,
Jim Finley
_________________________
"Tell me, I'll forget".
"Show me, I'll remember".
"Involve me, I'll understand".
Top
Work Gear for Electricians and the Trades
#65389 - 05/01/06 09:12 PM Re: Circuit Breakers
frenchelectrican Offline
Member
Registered: 02/06/03
Posts: 939
Loc: Wi/ Paris France { France for ...
gernally yes but a catch is it depend on the conductor as well

devices 800 amp and over

where the over current device is rated 800 amp and over the conductors ampcity it protected shall be equal or greater than rating of conductors

device of 800 amp or less
the next stanard overcurrent rating shall be permitted to be used provied all the following condtion are met:

1] the conductors being protected are not part of multioutlet branch circuit supplying for cord and plug connected portable loads

2] the ampacity of the conductors does not corponded with the standard ampre rating of the fuse or circuit breaker without overload adjustment above the ratings

3] the next higher standard rating do not excess of 800 amperes. [ see above ]

merci, marc

[This message has been edited by frenchelectrican (edited 05-02-2006).]
_________________________
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

Top
#65390 - 05/02/06 03:03 PM Re: Circuit Breakers
Dave T Offline
Member
Registered: 01/22/05
Posts: 155
Loc: Waukesha, WI, USA
It's simple. Calculate the load (125%+100%), select a cable to carry the load (the cable must carry the calculated load), select a breaker to protect the cable (the breaker is based upon the cable's rated ampacity noting the 800a up/down rule as the other poster pointed out).
Top

Member Spotlight
Member Since: 02/23/13
Posts: 204
New in the Gallery:
SE cable question
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box


Who's Online
2 registered (Admin, sparkyinak), 74 Guests and 9 Spiders online.
Key: Admin, Global Mod, Mod
 
New in the Gallery:
SE cable question
 
Top Posters (30 Days)
Admin 49
HotLine1 43
gfretwell 18
Ruben Rocha 12
Trumpy 9
 
Newest Members
Freecrowder, clee512, Jdscott2005, FAIZAN, Regitest2

ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals