I have an existing solar PV system; conduit to the house carries DC pairs for two "strings" of solar panels plus EGC ground. It'd be very convenient for wiring of an EV charger (EVSE), if I could run its AC wiring in the same conduit. The EVSE would mount near the solar panels.
Conduit fill is no issue. We're talking five 10awg wires (for the solar PV) and three 8awg wires (for the EVSE). The conduit is 1-1/4". All the conductors are THWN.
I suppose Table 310.15.B.3.A requires me to de-rate the wires by 80%. Not an issue for the solar wiring, as the panels' short-circuit current is about 9 amps. But the EVSE can draw 40 amps (continuous, meant to be protected by a 50-amp breaker).
(1) Does Table 310.15(B)(16) and the 80% de-rating prevent my running the 8awg for the EVSE in the same conduit as the solar PV ? (I'm unclear which column to use).
(2) Do I need to run an EGC for the EVSE, or does the existing 10awg wire for the solar suffice ? The existing wire grounds the panels and racking and there is a ground rod installed at the panels.
(3) Is it ok to mix AC and DC wiring like this, if so is there some other restriction that would disallow it ?
NOTE: To those who have answered my question about adding an EVSE to an existing subpanel, this question refers to a different site.
Best Answer
That 4-6 wire derate in 310.15(B)(3)(a)
Afraid so. The 4-6 wire derate will affect your circuit, smashing the 8 AWG copper down to 44 amps. 8 AWG Cu (and 6 AWG Al) are odd ones...the way the rounding happened, the 90C rating is unusually close to the 75C rating.
And since they don't let me help design EVSEs, major EVSEs do not have a 44A setting :)
Moot point anyway.
Solar + AC in the same conduit
Doesn't look that way.