I am filling up a room with various electrical equipment, I need about 3500 watts and I rather not use the circuit that's already in the room

Adding two 20 amp 120 volt circuits would provide 3840 watts capacity for future load.

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Originally Posted by jdespa84

i am filling up a room with various electrical equipment, i need about 3500 watts and i rather not use the circuit thats already in the room

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A standard 12 awg conductor on a 20 Amp circuit can actually supply up to a rated 30 Amps if the type insulation supports the temperatures permitted, otherwise you need to run a branch circuit to match the load(s) you are adding. (I.e. A 10 awg 30 amp branch circuit to new outlets with a breaker properly sized to protect the circuit wiring will handle over 3.5 kW continuous.)

Nmwirez,

Your advice is incorrect.

#12 copper wire, no matter the temp rating of the insulation is, cannot be protected by a overcurrent protection device larger than 20 amp, see the asterisk next to #12 wire listed in Table 310.16, that refers to NEC 2008 Section 240.4(D).

Also, a 30 amp circuit cannot serve standard 15 or 20 amp receptacles.

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Originally Posted by tkrussell

Nmwirez,

Your advice is incorrect.

#12 copper wire, no matter the temp rating of the insulation is, cannot be protected by a overcurrent protection device larger than 20 amp, see the asterisk next to #12 wire listed in Table 310.16, that refers to NEC 2008 Section 240.4(D).

Also, a 30 amp circuit cannot serve standard 15 or 20 amp receptacles.

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Please read the information carefully. A #12 AWG copper wire is rated for 30 Amps for a 90 C rated conductor. See NEC Art 310.16 (2011) for ampacity factoring. Depending on conditions of duty rating and voltage, a 12 AWG can most certainly use a higher overcurrent protection device. The OP did not detail what conditions were being applied let alone receptacle or switch listed grade devices. Please remove the incorrect from your comment.

No, I will not retract that your advice is incorrect.

See Table 310.15(B)(16) of the 2011 edition of the NEC.

Adjacent to the #12 copper is two **, see footnote at bottom of Table 310.15(B)(16):

** Refer to 240.4(D) for conductor overcurrent protection limitations

Section 240.4(D) 5 states: #12 AWG Copper. 20 Amperes
Simply, the maximum fuse or circuit breaker to protect a #12 copper wire, no matter the temp rating of insulation, shall not exceed 20 amps.

The higher amp ratings shown under the 75 C or 90 C degree columns may be used for derating purposes, which is irellevant to this question.

Sorry, but I will not back off this.

nmwirez... Please do not offer incorrect or unsafe advice which is clearly not up to the NEC.
This is a do it yourself site and wrong, incorrect and irresponsible information like that which you posted can be dangerous to other members without sufficient knowledge to understand just how incorrect you are.

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Originally Posted by Missouri Bound

nmwirez....Please do not offer incorrect or unsafe advice which is clearly not up to the NEC.
This is a do it yourself site and wrong, incorrect and irresponsible information like that which you posted can be dangerous to other members without sufficient knowledge to understand just how incorrect you are.

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Hi Missouri Bound,

I agree if this is applicable to home wiring in general. The data I gave is in reference to installations beyond the 240.4(D) applications that are additional in 240.4(E) or (G) conditions.

See Table 240,4(G) used in electrical conductor size factoring commonly applied in refrigeration and air-conditioning equipment OCPD's such as 25Amp fused or breaker protected 12 AWG runs. This is motor equipment Article 440 applied and mainly commercial but also in residential A/C equipment.

Bundled and ambient correctional adjustments are factored by selecting the type insulation ratings for those higher adjusted temperature conditions.

As tkrussel is referring to the 240.4(D) maximum permitted requirements that apply to nm wiring for common conductor sizes 14 awg= 15A, 12awg=20A, 10awg=30A, 8awg=40A... and so on, can be found in the Table 310.16 (2008) or the Table 310.15(B)(16) (2011) Allowable Ampacities charts of insulated conductors in the NEC. My statements are accurate but broad and did not apply technically in most standard dwelling in-wall circuit instances. nmwirez

I appreciate your answer and I understand where you are coming from completely. And I'm glad that you acknowledge that your advice to the poster was in error for the application and situation as stated.