patsy
Member
- Location
- new jersey
trying to figure out what table to use roe sizing wire for a 60 amp sub panel
trying to figure out what table to use roe sizing wire for a 60 amp sub panel
There are no special rules for sub panels. Use whatever table applies to the method of installation. Most of the time, that will be 310.16, but you didn't say whether the wires will go underground, or in cable tray, or in conduit.
You can't use that table for a subpanel.If it's resi, depending on what you're doing, you may be able to use table 310.15(B)(6), but I doubt that's the answer.
You can't use that table for a subpanel.
Actually yes you can. If you are doing a panel upgrade and relocation to add say an AC and if all of the other loads remain on the original panel board, you can size the feeders per that table. 310.15(6)
John
I am not sure if I understand what you posted.
Would you mind teaching an old guy a new trick?
Sorry, I was just rereading that and I left our the dwelling part.
Let's say you have a 100 amp service and you want to ad AC and need to do an upgrade. You could put a 200 amp service next to the old 100 amp service and if all you do is refeed the 100 amp panel from the new 200 amp service, you can use table 310.15(B)(6) to size the conductors.
Make sense?
As long as the major load for the house still is on the subpanel, you can apply this section.
Now, the revision in the 1996 NEC of that portion in Note 3 which now reads "the main power feeder to a dwelling unit", recognizes application of Note 3 for just that type of feeder.
Been in the code for a long time.
310.15(B)(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For individual dwelling units of one-family, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service-lateral conductors, and feeder conductors that serve as the main power feeder to each dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit. The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.61, and 230.42 are met.
John, I am not budging on this one, I can dig up the CMP statements if you would like.
The idea is to ensure the load diversity that is expected for an entire dwelling unit.