1000v DC PV Disconnects

[Phil Timmons]

Of course there’s a DC disconnect at the SMA TriPower inverter, just not physically exiting the array itself.

Yeah, that pushes things into needing to move the Inverter right up to the array, at least for Rooftop installs.

But since you are ground mount, maybe you can install the SMA at or near the array? Otherwise you are bringing the DC runs to (where?) (a building?) -- you know you cannot bring that DC inside the building, right? Without the rapid shutdown, I mean. But I see folks doing that. Bringing the DC inside I mean - wiping out the entire advantage of having not put the Solar on the roof.

Other thing have noticed with SMA is that by putting the On/Off for AC and DC on opposite sides -- we now have inspectors calling for Working Space (Art 110) on BOTH sides of the inverter, along with wanting us to put protection over/around the exposed DC 1000V cables that enter on the back. mho -- SMA should be revisiting the ENTIRE design of this thing.

 

[BackCountry]

Yeah, that pushes things into needing to move the Inverter right up to the array, at least for Rooftop installs.

But since you are ground mount, maybe you can install the SMA at or near the array? Otherwise you are bringing the DC runs to (where?) (a building?) -- you know you cannot bring that DC inside the building, right? Without the rapid shutdown, I mean. But I see folks doing that. Bringing the DC inside I mean - wiping out the entire advantage of having not put the Solar on the roof.

Other thing have noticed with SMA is that by putting the On/Off for AC and DC on opposite sides -- we now have inspectors calling for Working Space (Art 110) on BOTH sides of the inverter, along with wanting us to put protection over/around the exposed DC 1000V cables that enter on the back. mho -- SMA should be revisiting the ENTIRE design of this thing.

There are 4 arrays stacked, I’m putting the inverter at the bottom of the first one. No building involved, otherwise we’d have to install RDS boxes for sure, which would negate the reason for choosing SMA over SolarEdge. I just like to have isolating disconnects for troubleshooting rather than having to walk 300 feet down to the inverter.

I also noticed the DC and AC disconnect switches are on opposite sides AND the conduit entry and string connections are perpendicular to that. I ordered their universal mount kit, this is going on a unistrut panel board on a concrete pad, I think I’ll just mount the inverter to the concrete pad so there’s room.

I don’t see any way to sleeve the strings either, I’m going to bring them up in a 3R box as close to the connectors as I can.

I agree, there should be an enclosure you can run pipe to on the DC connections.

My impression is that the TriPower is much better suited for roof mount with the design having connectors and the opposite sides disconnect design.

 

[solarken]

For 300 feet between inverter and array, that adds 600 feet of conductor length contributing to voltage drop. If you did transition from PV wire at the array to XHHW-2 wire for the underground run, and then back to PV wire at the inverter for the amphenol connections, Southwire XHHW-2 is rated for 1000V in sizes 8AWG and larger, so using 8AWG would get you the voltage rating you need plus reduce the voltage drop, and with slightly smaller conductor diameter than 10AWG PV Wire. Not sure if all the back and forth is worth it to you but thought I would suggest.

 

[BackCountry]

For 300 feet between inverter and array, that adds 600 feet of conductor length contributing to voltage drop. If you did transition from PV wire at the array to XHHW-2 wire for the underground run, and then back to PV wire at the inverter for the amphenol connections, Southwire XHHW-2 is rated for 1000V in sizes 8AWG and larger, so using 8AWG would get you the voltage rating you need plus reduce the voltage drop, and with slightly smaller conductor diameter than 10AWG PV Wire. Not sure if all the back and forth is worth it to you but thought I would suggest.

I’ll check in on cost for XHHW-2, I’ve never used it — 1000v is all new territory for me. I appreciate the suggestion.

 

[Carultch]

I’ll check in on cost for XHHW-2, I’ve never used it — 1000v is all new territory for me. I appreciate the suggestion.

Take a closer look at the inverters. If you have the CORE-1 inverters, that inverter forces you to expose the final foot of the DC conductors, as they connect to the inverter's bulkhead connectors, rather than having a closed cabinet for terminating the conduit and wire. 690.31 requires PV wire where exposed.

XHHW-2 is good as in-conduit wiring for 1000V, as long as you are sure you are getting the 1000V wire. At one point, this wire type was 600V rated. This is something your supplier could easily overlook, you get confirmation that it is 1000V if needed for your application.

 

[BackCountry]

Take a closer look at the inverters. If you have the CORE-1 inverters, that inverter forces you to expose the final foot of the DC conductors, as they connect to the inverter's bulkhead connectors, rather than having a closed cabinet for terminating the conduit and wire. 690.31 requires PV wire where exposed.

XHHW-2 is good as in-conduit wiring for 1000V, as long as you are sure you are getting the 1000V wire. At one point, this wire type was 600V rated. This is something your supplier could easily overlook, you get confirmation that it is 1000V if needed for your application.

Understood, thanks for the heads up.

I’m with you on the CORE-1 PV connector bulkhead. That, combined with the AC and DC disconnects being opposite of one another isn’t the best in my scenario.

I got the UM-10KIT with it, I think we’ll rotohammer in a few anchors and pad mount it, that way we can tie the PV wire in and probably get stuck using 2” LMFC to bring the AC side up to the disco.

The only problem I see is joining the PV wire to the XHHW-2, the only connector I can find that’s 1000v listed is Ideal Twister Pro’s — and they’re discontinued.