3 ms·
> With 12AWG, depending on the cable type and rating, you can bring 20-30A (90C rated) of power to go with your fiber in the same pull. Wire size is calculated
by quickthrowman 3y ago
> With 12AWG, depending on the cable type and rating, you can bring 20-30A (90C rated) of power to go with your fiber in the same pull.
Wire size is calculated off the 75C column of the ampacity table (NEC 310.16) so #12 wire is only good for 25A.
The reason being, there are almost no circuit breakers rated for 90C, the terminals/lugs are only rated for 75C in nearly all cases.
Forum thread w discussion: https://forums.mikeholt.com/threads/90-degree-or-75-degree.2551455/ https://forums.mikeholt.com/threads/90-degree-or-75-degree.2...
- Moto7451 3y agoFor residential, yes, but commercial is a different story. Schneider will happily sell you 90c rated equipment beyond the wire. They provide excellent guidance: https://www.productinfo.schneider-electric.com/0110db9901wiretempratetermdb/0110db9901-wire-temp-ratings-and-terminations/0110DB9901%20Wire%20Temp%20Ratings%20and%20Terminations/English/0110DB9901%20(bookmap)_0000485497.xml/$/TheNECRules-D1995BA7#EquipmentRatedFor100AOrLessNEC110.1-D1B8465D2 https://www.productinfo.schneider-electric.com/0110db9901wir... I don’t think anyone needs shared fiber and 12ga cable in a home setting anyway. The NEC also defers to UL and similar bodies for installations being cleared so the complexities go beyond the basic NEC guidance, especially for the exotic stuff out there.
- quickthrowman 3y agoI’m a commercial electrical project manager and I’ve never seen a spec call for 90C rated breakers. I bought dozens of panelboards last year from multiple manufacturers, including Square D. You also need equipment lugs/terminal blocks/wire nuts rated for 90C. I’m not saying 90C rated parts don’t exist, it’s just uncommon enough that you select wire based on the 75C column by default, even in a commercial setting.