Planning install; running conduit for future: Question on sizing/mixing conductors

[Spektre]

I need to install EMT conduit from my main panel into my attached garage for EV power now. The conduit will contain 3x #6 for 240V/30A to EVSE and be surface mounted approximately 50 feet across my flat roof .

When I am ready to install solar, I want to install 2x SMA string inverters in the garage instead of outside, and would like to use the same conduit for the AC run back to the panel.

Since the conduit needs to penetrate the flat roof on my garage, can I also use it to feed the DC wiring from the panels in to the inverters, or is mixing the DC-in with the AC-out in the same conduit a bad idea?

[SunEagle]

Yep. Mixing AC and DC is not a good idea. The same came be said for low voltage and high voltage wire. Even running two different voltages next to each other might cause noise due to the magnetic fields being generated. There are some basic electrical principals that can be found on the internet about running wire and spacing based on codes and principals. You might want to explore that before you dig and bury the pipe.

Oh last tip. Any wire that is run outside (even in conduit) must be rated for wet locations and EMT is not a good type of conduit that will hold up in wet environments.

[foo1bar]

Oh last tip. Any wire that is run outside (even in conduit) must be rated for wet locations and EMT is not a good type of conduit that will hold up in wet environments.

I think the vast majority of residential solar installs use EMT for the conduit.
And I haven't seen a lot of complaints about EMT not holding up to normal rain, snow, etc. (But I could believe that sea-spray probably would rust it out before too long.)


For the OP:
For an EV charger, I probably would look at doing something different than EMT on the roof.
Either keep everything under the roof (conduit on the ceiling of garage? Possibly could do PVC or EMT.)
Or do IMC or RMC on the roof so it's less likely to get water coming in the conduit and making it's way down to the charger.
But that's just me.

Also don't forget to make sure it's sufficient distance off the roof so it isn't as much derating because of temperature.
(And make sure your electrician has accounted for the necessary derating)

[Spektre]

No digging/burying necessary - the garage is attached to the house and the conduit will run across the roof. Here in Scottsdale, AZ it's pretty dry and the plastics really don't cut it in the rooftop temperatures we see around these parts in August!

I plan on using #6 THWN-2 for the wet/90c rating.

Just found in NEC 2014 690.31 that PV source circuits can't be contained in the same conduit as inverter output circuits.