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#80828 05/30/02 03:34 PM
Joined: May 2002
Posts: 68
E
Eandrew Offline OP
Member
I'm confused over ampacity adjustments.

Table 310-16 is based on a continuous load without exceeding the insulation temp. rating -article 100

so why is the 80% corretion factor for a continuous load needed? Is this lower ampacity not built into table 310-16?

Is it necessary to lower the normal ampacity in 310-16 by 20% and then size the wire and overcurrent protection to 125% of that value. -Erik

2017 / 2014 NEC & Related Books and Study Guides
#80829 05/30/02 07:44 PM
Joined: May 2002
Posts: 1,716
R
Member
Eandrew, article 310-16 is correct. The conductors are rated at 100% and are not the issue in the 80% value. The 80% concerning continuos loads are for OCPD,s and the heat at the connection. If the OCPD is rated for 100% this will not be an issue. I assume by your use of the dash you are refering to the 99 code and if this is the case see 384-16d

Roger

#80830 05/31/02 01:36 AM
Joined: May 2002
Posts: 68
E
Eandrew Offline OP
Member
thanks rodger,

I was thinking that the 80% and 125% related to different things. It is clear to me now. Continuous loads are limited to 80% of the overcurrent device rating. A little algebra and you have an overcurrent device must be at 125% of the continuous load. got it, thanx.

#80831 05/31/02 05:16 PM
Joined: May 2002
Posts: 1,716
R
Member
You're welcome.

Roger


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