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Can I take a 120v 20amp circuit slightly past 80% continuously?

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  • Can I take a 120v 20amp circuit slightly past 80% continuously?


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Answer #1 | 19/12 2013 15:01
Your home wiring is good for 100%, I don't know where you got this 80% figure, it may be a precautionary advice for devices like generators or inverters. Go right ahead, if the breaker trips then either your circuit is overloading, or you may have an oversensitive breaker.
Answer #2 | 19/12 2013 17:05
It should be good
Answer #3 | 19/12 2013 18:05
It should be ok.. As long as the max volts don't exceed 120v it will not trip.
Answer #4 | 19/12 2013 18:27
Not legally. I have never seen servers that draw max current continuously, if yours do it would be a violation, but likely not trip under normal operating conditions. Your biggest threat will probably be that any weak connections or minor damage will become apparent sooner, or it will trip during brown out due to preheating of the internal overload heating element in the breaker shortening the inverse time delay curve. 80% is not just a good idea, it is code code for wire and breakers for continuous loads (defined as 3+ hours) or for single cord connections. It is the standard used by engineers when designing products, and exceeding that level will cause shortened product life. The National Electrical Code uses 125% in various sections, some that are applicable are: NEC 220.20(A) Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the rating of the overcurrent device shall not be less than the noncontinuous load plus 125 percent of the continuous load. NEC 210.19 (A)(1) Branch-circuit conductors shall have an ampacity not less than the maximum load to be served. Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads...shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load. NEC 210.21(B)(2) Table for Maximum Cord-and-Plug-Connected Load to Receptacle which can be seen at http://www.freenec.com/T28.html The code requires that loads exceeding 80% must be divided into multiple circuits. If the load is a single cord connected device that exceeds 80% then code requires/allows the next size receptacle, a 30 amp with a maximum of 24 amps on a 30 amp breaker, the receptacle would have to be wired with #10 wire. NEC 220.20 requiring 125% doesn't allow receptacles to be connected to breakers larger than the overcurrent protection rating of the receptacle, 210.21(B)(3) still applies, and the small conductor requirements in 240.4 also apply limiting #12 to 20 amps and above that requiring #10 for up to 30 amps.

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