To Transition or not to Transition, PV wire to THHN

[garybryan33]

I have seen installations where the PV wire is run into a junction box somewhere next to the solar panel rails, transitioned to THHN, and from that point on in conduit into the structure. Instead, could I run my PV wire into a junction box to collect them all and send them out via conduit into the structure ultimately ending at the DC disconnect switches where they will be transitioned to THHN wire?

Secondly, May the conduit be electrical grade grey PVC? The structure is a carport of sorts with 3 walls, and siding on the exterior. I have added fire-rated sheet rock in the immediate area where the wall-mount batteries and the 18K will live. I am not grid-tied, not interested in selling back to the man. I do plan on adding a transfer switch. That's a different subject. Thank you

 

[dougbert]

PV cables when greater than 32 volt must be in metal conduit when on the roof and when entering and inside a building
PVC conduit can be used outside to bring the PV cables to the house JBox converting to metal

 

[1201]

Pv wire is a lot thicker than thhn so you are going to need much larger conduit if you decide to do it that way

 

[Zwy]

I have seen installations where the PV wire is run into a junction box somewhere next to the solar panel rails, transitioned to THHN, and from that point on in conduit into the structure. Instead, could I run my PV wire into a junction box to collect them all and send them out via conduit into the structure ultimately ending at the DC disconnect switches where they will be transitioned to THHN wire?

Secondly, May the conduit be electrical grade grey PVC? The structure is a carport of sorts with 3 walls, and siding on the exterior. I have added fire-rated sheet rock in the immediate area where the wall-mount batteries and the 18K will live. I am not grid-tied, not interested in selling back to the man. I do plan on adding a transfer switch. That's a different subject. Thank you

Metal conduit only inside a structure containing PV wires.

 

[Quattrohead]

Permit and inspections or not?
Proper pv cable is rated for UV exposure and burial so you can leave it exposed, then transition it in a junction box to whatever you want to run. DC must be in a metal conduit or MC rated cable inside a dwelling.

 

[garybryan33]

Metal conduit only inside a structure containing PV wires.

Metal conduit only inside a structure containing PV wires.

Actual PV wire and THHN running high DC voltage, correct? Thank you

 

[seneysolar]

I like using the Midnite combiner box like the MNPV3 or MNPV6 out at the panels. PV in to the box, each string gets its own breaker.
The bus on the combiner makes a good transition to whatever wire you are running to the house.

 

[garybryan33]

Permit and inspections or not?
Proper pv cable is rated for UV exposure and burial so you can leave it exposed, then transition it in a junction box to whatever you want to run. DC must be in a metal conduit or MC rated cable inside a dwelling.

No permit, however I am doing everything to meet code. Is MC cable rated for outdoor runs? for example, junction box on roof to the interior of the structure.

 

[garybryan33]

I like using the Midnite combiner box like the MNPV3 or MNPV6 out at the panels. PV in to the box, each string gets its own breaker.
The bus on the combiner makes a good transition to whatever wire you are running to the house.

These are roof mounted panels, the midnite combiner looks more suitable for ground mounted panels. Am I mistaken?

 

[Brett V]

These are roof mounted panels, the midnite combiner looks more suitable for ground mounted panels. Am I mistaken?

I know it’s been done, but I’d think long and hard about putting a combiner box on a roof.

 

[seneysolar]

I know it’s been done, but I’d think long and hard about putting a combiner box on a roof.

True, could be inconvenient, but be careful combining strings into larger wire without protecting the smaller wire.

If combining say 6 strings of 10ga pv wire. If one of those finds a path to ground, it now has the 5 other strings backfeeding to ground through that single wire, unprotected.

 

[timselectric]

If you combine 6 strings, they must be individually fused.

 

[Brett V]

True, could be inconvenient, but be careful combining strings into larger wire without protecting the smaller wire.

If combining say 6 strings of 10ga pv wire. If one of those finds a path to ground, it now has the 5 other strings backfeeding to ground through that single wire, unprotected.

I agree it might be unavoidable but if there’s a way to get those six strings in to a combiner on the side of the house somewhere closer to the ground, I’d put my effort there.

 

[Zwy]

Actual PV wire and THHN running high DC voltage, correct? Thank you

Any wire running high PV voltage.

 

[garybryan33]

I agree it might be unavoidable but if there’s a way to get those six strings in to a combiner on the side of the house somewhere closer to the ground, I’d put my effort there.

There are 3 strings in series any junction box on the roof would transition from PV wire to THHN, into the structure and through individual DC disconnects. Two of the arrays will be paralleled at input 1 of the inverter, EG4 18K.

 

[timselectric]

There are 3 strings in series any junction box on the roof would transition from PV wire to THHN, into the structure and through individual DC disconnects. Two of the arrays will be paralleled at input 1 of the inverter, EG4 18K.

EG4 18kpv

 

[garybryan33]

Any wire running high PV voltage.

Would this MC Cable meet NEC guidelines to run on the roof and into the structure?

Parking Deck/Lot Cable - Interlocked Galvanized Steel Armor w/ Overall PVC Jacket - Type MC​

Standards, References, & Ratings

• ▲UL 66, 83, 1569, 1581, 2556, File Number: E80042
• ▲PROP65 - Warning use caution and ventilation when cutting or performing hot work-Cancer|www.P65Warnings.ca.gov
• ▲NEC® 230.43, 300.5, 330, 392, 396.10(A), 501, 502, 503, 504, 505, 511.7, 513.7(A), 514.7, 515.7(A), 516.7(A), 530, 680.21(A)
• ▲UL Listed Sunlight Resistant
• ▲Hazardous locations up to Class I & II, Div. 2 and Class III, Div. 1 & 2 (NEC® Articles 501, 502, 503, 530)
• ▲Federal Specification A-A-59544 (formerly J-C-30B)

 

[Zwy]

Would this MC Cable meet NEC guidelines to run on the roof and into the structure?

Parking Deck/Lot Cable - Interlocked Galvanized Steel Armor w/ Overall PVC Jacket - Type MC​

Standards, References, & Ratings

• ▲UL 66, 83, 1569, 1581, 2556, File Number: E80042
• ▲PROP65 - Warning use caution and ventilation when cutting or performing hot work-Cancer|www.P65Warnings.ca.gov
• ▲NEC® 230.43, 300.5, 330, 392, 396.10(A), 501, 502, 503, 504, 505, 511.7, 513.7(A), 514.7, 515.7(A), 516.7(A), 530, 680.21(A)
• ▲UL Listed Sunlight Resistant
• ▲Hazardous locations up to Class I & II, Div. 2 and Class III, Div. 1 & 2 (NEC® Articles 501, 502, 503, 530)
• ▲Federal Specification A-A-59544 (formerly J-C-30B)

Yes, MC will meet the NEC code for PV. I run MC to my charge controllers, it is shown in a video about the EG4 MPPT's I did last year.

Just remember to use the plastic bushing on the ends to prevent wire chafing.

 

[garybryan33]

Yes, MC will meet the NEC code for PV. I run MC to my charge controllers, it is shown in a video about the EG4 MPPT's I did last year.

Just remember to use the plastic bushing on the ends to prevent wire chafing.

Awesome. Can you share a link to that video? Thank you

 

[Zwy]

Awesome. Can you share a link to that video? Thank you

Youtube channel is Doc Zwy. I don't want to appear I'm promoting my channel. I have no plans to monetize it or ever get a cent from it. Just share some information and demonstrate how I did things in a visual format. In a forum like this it isn't easy to show some things.