Is this a valid PV disconnect setup?

[Deleted member 23531]

This is a 2 pole pv ground fault interrupt device

This device "(PNL-GFDI-80D) is designed for use with systems that have two charge controllers that are fed by two separate PV arrays". If you look at the documentation they don't show both leads (+) and (-) going through the device using the two poles, but rather two (+) leads from two separate arrays using the two poles. (Page 9 shows the dual pole wiring). This is similar to standard house wiring how the breakers are on the hot leads and the neutral leads are just shorted together using a bus bar.

I believe this part from OutBack is functionally equivalent to the Midnite GFP device I mentioned above. The only difference, I think, is that they sell it in a 2x version for two separate arrays protected by the same negative-to-ground sensor. The Midnite part is for a single array.

Edit: I guess another difference is they show it positioned between the solar charger and the battery, as opposed to between the PV and the solar charger. I think I'd rather put it between the PV and the solar charger since it seems more likely a short would develop in the wiring to all the panels and the panels themselves than on the solar charger / battery connection. But, this is just a guess at which failure mode is more common.

 

[Deleted member 23531]

Reading through OP's comments again I think I'm getting pretty far afoot from what he/she is asking. In my opinion this is the summary that I'm operating under; please correct me if I'm wrong:

- for a disconnect, just put a breaker on the (+) line. polarized is fine as long as it's installed in the correct direction; non-polarized would be better in some cases, particularly incorrect wiring, but they cost more.

- there is no need for (+) and (-) disconnects. What would the (-) one even be doing? Just disconnect the (+) side with the breaker, just like house wiring. Both Midnite and Outback show it this way in their wiring diagrams; I'm not sure where you're seeing recommendations to disconnect both (+) and (-).

- do include a DC-rated ground fault protection device, such as the aforementioned Midnite or Outback products.

- don't use the ground-fault protection device as a disconnect, per multiple manufacturers' messaging and also the NEC. You need to keep the battery-negative-to-ground connection intact while disconnecting the circuit loops of the two power sources (battery and PV array) to work on your system safely. In other words: always leave the ground-fault switch in the "on" position; it should only ever get switched off by a true fault condition (which you then need to fix).

 

[rmaddy]

Oops - ignore

 

[rmaddy]

Reading through OP's comments again I think I'm getting pretty far afoot from what he/she is asking. In my opinion this is the summary that I'm operating under; please correct me if I'm wrong:

- for a disconnect, just put a breaker on the (+) line. polarized is fine as long as it's installed in the correct direction; non-polarized would be better in some cases, particularly incorrect wiring, but they cost more.

- there is no need for (+) and (-) disconnects. What would the (-) one even be doing? Just disconnect the (+) side with the breaker, just like house wiring. Both Midnite and Outback show it this way in their wiring diagrams; I'm not sure where you're seeing recommendations to disconnect both (+) and (-).

Using just one breaker on the positive PV wire was my original plan. It's just that I've seen many references to putting a breaker on both the positive and negative wires. It always seemed odd since nowhere else (switches, fuses, other breakers) do you also do it on the negative wire. But there must be some reason (maybe not a good one) there are so many references to putting a breaker on both PV wires.

- do include a DC-rated ground fault protection device, such as the aforementioned Midnite or Outback products.

I need to look into these more.

- don't use the ground-fault protection device as a disconnect, per multiple manufacturers' messaging and also the NEC. You need to keep the battery-negative-to-ground connection intact while disconnecting the circuit loops of the two power sources (battery and PV array) to work on your system safely. In other words: always leave the ground-fault switch in the "on" position; it should only ever get switched off by a true fault condition (which you then need to fix).

Thanks

 

[DerpsyDoodler]

This device "(PNL-GFDI-80D) is designed for use with systems that have two charge controllers that are fed by two separate PV arrays". If you look at the documentation they don't show both leads (+) and (-) going through the device using the two poles, but rather two (+) leads from two separate arrays using the two poles. (Page 9 shows the dual pole wiring). This is similar to standard house wiring how the breakers are on the hot leads and the neutral leads are just shorted together using a bus bar.

Correct. The negative pole becomes common for the solar array strings that wire through it, and is how the breaker I linked has to be wired for the ground fault protection to work properly.

OP was originally asking about a disconnect. This device will fulfill that and provides ground fault protection.

 

[rmaddy]

It's been 10 days since I sent an email to support@midnitesolar.com and I have not received a reply. Oh well. I've decided to just put one breaker on the PV positive wire near the SCC. Makes things much simpler. I finished up that wiring today. I left some extra PV negative wire inside the breaker box so I can always add a breaker to that one if I ever determine it's really necessary to have a breaker on both PV wires.

 

[will_fish]

@rmaddy - Did you ever hear back from midnite solar? I'm wondering the same thing on the PV negative wire breaker. I did run across this wiring diagram (which is currently on the midnite solar website) for the MNPV12 related to the PV negative wire breakers. It seems to show the negative wires going into the bottom of the breakers (see top of page 7 and also added below). They indicate that this is specific for "transformerless" inverters but I'm really wondering if the NEC code being referenced is still valid.

 

[rmaddy]

Did you ever hear back from midnite solar?

No, I never did. I still have just the one breaker installed.

I have no idea if that diagram is relevant to my setup.

 

[timselectric]

Dc current flows in one direction. When using a polarized breaker on a positive , wire according to the markings. When using it on a negative wire, reverse the connection to the markings. (Input vs output)

 

[Bud Martin]

It's been 10 days since I sent an email to support@midnitesolar.com and I have not received a reply. Oh well. I've decided to just put one breaker on the PV positive wire near the SCC. Makes things much simpler. I finished up that wiring today. I left some extra PV negative wire inside the breaker box so I can always add a breaker to that one if I ever determine it's really necessary to have a breaker on both PV wires.

I look at it this way, they do not install inline fuse/OCD on both positive and Negative wires of the panel, do they? I only put DIN fuse holder on my Positive wire feeding my SCC.

 

[timselectric]

Overcurrent protection devices only need to be installed on one wire of the circuit. I only recommend a 2 pole disconnect for maintenance purposes.

 

[rmaddy]

I look at it this way, they do not install inline fuse/OCD on both positive and Negative wires of the panel, do they? I only put DIN fuse holder on my Positive wire feeding my SCC.

These are PV disconnect breakers, not overcurrent protection.

 

[CamoGreg]

These are PV disconnect breakers, not overcurrent protection.

From what I read elsewhere:

NEC 2020 Article 690.13 section (E) States that “ The PV System disconnecting means shall simultaneously disconnect the PV system conductors that are not solidly grounded from all conductors of other wiring systems.

Since camper electrical systems are generally NOT grounded, this means that both the positive and negative conductors from the solar array need to be able to be simultaneously disconnected, and a dual pole breaker does exactly that.

 

[rmaddy]

From what I read elsewhere:

Right. And the whole point of this thread is to figure out how to properly wire two separate MNEPV polarized breakers so I can have a disconnect on both PV wires.

 

[carbonchemist]

Right. And the whole point of this thread is to figure out how to properly wire two separate MNEPV polarized breakers so I can have a disconnect on both PV wires.

Did you ever find an answer to your problem? I am trying to figure out the same thing. Thank you in advance.