Wiring a DC disconnect

[rubiks1]

Hello
Have a code/how to do it question for everyone here. When wiring a DC disconnect for solar do you have to bring the negatives into the box even though they do not connect to anything or just the positives? The 4 ga wire I will be connecting is the combined wired (from 3 solar panel strings on breakers) coming from a midnight solar MNPV3 combiner to the DC disconnect, from the DC disconnect to a midnight solar epanel which has the PV + buss bar.

Thanks in advance

[sensij]

What model inverter or charge controller are you going to from the disconnect?

[rubiks1]

What model inverter or charge controller are you going to from the disconnect?

The inverter will be a Outback GVFX 3524 and a Outback Flexmax 60.

[Amy@altE]

Just for wire management purposes, it might be easier to bring the negative through the disco. If you have conduit going from the PV3 going into the disco, then from the disco to the ePanel, it makes sense that the - wire will be in there. But it shouldn't be disconnected, just passed thru.

[rubiks1]

Just for wire management purposes, it might be easier to bring the negative through the disco. If you have conduit going from the PV3 going into the disco, then from the disco to the ePanel, it makes sense that the - wire will be in there. But it shouldn't be disconnected, just passed thru.

Thanks Amy. Does the negative have to be in there? Can I leave it out as it will save me money on wire.

[Amy@altE]

Not following you. You need to bring the + and - from the PV6 into the ePanel in conduit. If the + is going to the disco, isn't the - going to be taking the same route? Or is the disco not on the way, and you are running a separate conduit to it?

[rubiks1]

Amy

Let me see if I can explain how it is going to lay out. This will be from the solar panels to the mnpv 3, to the dc disconnect and back to the epanel.

3 strings of solar (2 panels per string) going to a mnpv3, positives landing on 15 amp dc breakers, negatives landing on negative bus bar, ground from ground rod landing on ground bus bar

Now this is where it gets janky. The only place to put the dc disconnect per code is on the side of the house next to the meter that's how my city wants it. These panels are on the flat roof so that means a 35 foot run to the left to the dc disconnect via 3/4 EMT. For the way back it will be 55 foot run up the side of the house from the dc disconnect, in the same 3/4 EMT, hit the mnpv3 and from there the negative and positive will leave the mnpv3 in another piece of conduit and connect into the epanel.

That is why I was asking about leaving out the negative since the disconnect only needs the positive to work and it saves me a lot of wire. If you are confused ( i am to ) send me a PM and we can go from there.

Thanks for the help!!!
Brad

[Amy@altE]

Gotcha. No, as far as I know, the negative does not need to make that crazy trip.

[rubiks1]

Gotcha. No, as far as I know, the negative does not need to make that crazy trip.

Thanks Amy!

[inetdog]

Gotcha. No, as far as I know, the negative does not need to make that crazy trip.

As long as the negative is solidly grounded somewhere, of course.
Otherwise it not only has to go through disco it needs to be interrupted there.

[Philippeberard]

The inverter will be a Outback GVFX 3524 and a Outback Flexmax 60.

You contact that person when you buy a solar hope they help you.

[BackwoodsEE]

rubiks1 You've no doubt got your system all done by now, but it looks to me (random guy on the Internet) like fulfilling the rapid shutdown requirement of NEC 2017 for a rooftop array also addresses your issue. Right below 690.13(A) ("The PV system disconnecting means shall be installed at a readily accessible location") there's an informational note that seems to say as much: "PV systems installed in accordance with 690.12 address the concerns related to energized conductors entering a building."