help finding an ariticle I had lost.

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jself

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Does anyone know what article requires you to not put more than 80% of a breakers rating load on the breaker. for example a 20A breaker would only be allowed to be designed for 16A above and beyond the whole continuous load 125%
 
Re: help finding an ariticle I had lost.

210.20(A) (2002 NEC) Gives you the 125% rule.

The 80% you are talking about is the same as the 125% rule. If you take a 16 amp circuit and apply the 125% rule you will get 20 amps. If you reverse this and apply 80% to the 20 amp circuit you will get 16 amps.

Hope this helps

Chris
 
Re: help finding an ariticle I had lost.

To show Chris's post; 125% is the inverse of 80%

20 x .80 = 16
20 / 1.25 = 16

16 / .80 = 20
16 x 1.25 = 20


Roger

[ November 14, 2005, 06:28 PM: Message edited by: roger ]
 
Re: help finding an ariticle I had lost.

so to that end that would mean that if I have a panelboard that has a 100A of feeder demand load on it then I can size the main breaker on that panel for 100A? I thought I would have to size that breaker for 125A for a safety factor.
 
Re: help finding an ariticle I had lost.

If the feeder did not serve any continuous loads, then yes. The 125% is only for continuous loads.

Chris
 
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