![]() But with #2 copper those cables are probably not any that would have that restriction. Remember you can't use the ampacities listed in the 90 C column except for certain circumstances. If your wire insulation is only listed in the 60C column then you can only use the ampacity of that column. If rated for both then your ampacities will come from the 75 c column when using individual wires or cables with insulation ratings that are listed in the 75C column or the 90 C coolumn. So any ampacities you use will come from the 60 C column. If you cannot identify which it is then 60 C termination must be used. Usually it will say rated for 60C/75 C termination. That information is obtained from the specifications sheet located on the circuit breaker panel door. is the equipment that each end of the feeder rated for 60 C terminations or 75 C terminations or both. Most likely #2 copper will be individual wires in conduit and likely to be thhn/thwn rated temperature insulation but could be other types of wire or cables. ![]() In a nutshell #2 copper will be either 95 amps or 115 amps depending on some factors.those being type of wire insulation and is the feeder between panels a certain type of cable like UF-B or SER cable or individual wires in conduit like thhn/thwn. These ampacities are used for various reasons along with temperature adjustments and deration adjustments as necessary. So that is a breif lay of the land on how you look at this table. You will never use the ampacities listed in the 90C column in a residence. All the wires in the 90 C column can be used at the ampacities of the wires in the 60 C and 75 C columns. You will also see the temperatures of 60 C, 75 C and 90 C. In your case you want 100 amps so if you look at the table left hand side 1st column you will see wire sizes and across the top you will see temp ratings and wire insulation types. So the applicable table is the first table listed.NEC table 310.16. However without going into a long drawn out story this table is not applicable to your situation since a feed from the main panel to a sub-panel is not a "main feeder" carrying the total load of the dwelling with the service equipment and meter. Your reference that #2 copper is rated 125 amps would be directed at the 310.15 b6 table. ![]() go to the right column just below the conduit fill tables to conductor characteristics the first table listed is for conductor ampacities for insulated conductors (table 310.16) the second is a calculator for wire size and the 3rd is the ampacity table for main service conductors and main feeders for single family dwellings (table 310.15 (b)(6). For your reference there are 2 tables located at this link. ![]() (3) The next higher standard rating selected does not exceed 800 amperes. (2) The ampacity of the conductors does not correspond with the standard ampere rating of a fuse or a circuit breaker without overload trip adjustments above its rating (but that shall be permitted to have other trip or rating adjustments). (1) The conductors being protected are not part of a multioutlet branch circuit supplying receptacles for cord-and-plug-connected portable loads. (B) Devices Rated 800 Amperes or Less The next higher standard overcurrent device rating (above the ampacity of the conductors being protected) shall be permitted to be used, provided all of the following conditions are met: Other wiring methods, including SER cable and pipe and wire, can use #3CU for 100 amps because they can use the 75 deg C column. This is pretty much for NM cable only since NM is about the only wiring method that uses the 60 deg column. Because there is no 95 amp breaker we round UP to 100 amps. Click to expand.HUH? Where did you get your information?
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