Questions about wiring through attic

[Fafrd]

I'm putting in a 3kW system and have good enough access in the attack that I am thinking about wiring the home run down I to the attic, out the and down the exterior wall to the switch. Here is what I was thinking to do and I would appreciate feedback as to whether there are any issues with this plan:

1/ SolarDeck through-roof enclosure below the final Microinverter - I'm hoping I can run the female interconnect cable right into it so that it can serve as my junction/combiner box (single-string)'

2/ Romex into the attic - The Romex probable needs to be clamped so hopefully I can position the Solardeck in a way that a short run of plastic conduit lands near a diagonal roof member to mount a junction box (which will only be used for the clamp - no actual electrical junction).

3/ Romex continues to the soffit where I can position a junction box. Ideally an electrical junction here but I could strip off the Romex sheathing if an electrical junction must be avoided.

4/ metal conduit along the exterior wall down to the switch.

Is there are reason this woukd be a problem?

My biggest questions are about how to mount/clamp the Romex at the Solardeck and whether I can use an electrical junction to switch from Romex to different conductors at the junction box under the soffit.

[Fafrd]

Found some pictures to demonstrate what I am considering:

For the through-roof connection / Solardeck, this is what I am hoping to do (solar cable directly into Solardeck):

Because I have a 3' clearance requirement to the ridge of the roof, I cannot make this type of connection above the panel and can either make it under the panel (so that the panel needs to be removed to gain access) or I can mount in this way beside the panel (above the upper rail if possible and otherwise above the lower rail.

Will either of these options work? Opinions appreciated.

I have images for alternatives as well but will put in a subsequent post...

[Fafrd]

I am thinking that in the worst case, I can mount a junction box at the end of the rail (where it will be accessible) and the run through conduit to a through-roof fitting like this install:

I am really hoping to avoid having to support a length of conduit on the roof and can mount the through-roof fitting as close to the junction box as possible or even under a panel if needed.

Would appreciate any advice as to the best way to get through the roof with the minimum number of holes possible (including conduit support holes). Ideally, I'd like only a single hole for the Solardeck fitting.

[Fafrd]

And within the attic, this picture shows the 'worst-case' where I am going to rigid metal conduit from the Solardeck fitting on, but I am hoping to use Romex if possible (because it will be the easiest way to get through the Sofit) and otherwise non-rigid conduit (metal or plastic). Any advice on which of these options meets code and which is preferable appreviated.

For the soffit side, I'm pretty sure I can run Romex up through a hole in the Soffit and grab ahold of it from the attic. With flexible conduit, I may or may not be able to do the same (depending on bend radius) but with a hole big enough to pass a right-angle fitting, I believe I should be able to feed flexible conduit through. With rigid conduit, I don't see any easy way to pass it through or to make a connection in the attic near the soffit.

This is all for a Microinverter-based AC system - any advice appreciated...

[Fafrd]

Found some pictures to demonstrate what I am considering:

For the through-roof connection / Solardeck, this is what I am hoping to do (solar cable directly into Solardeck):

Because I have a 3' clearance requirement to the ridge of the roof, I cannot make this type of connection above the panel and can either make it under the panel (so that the panel needs to be removed to gain access) or I can mount in this way beside the panel (above the upper rail if possible and otherwise above the lower rail.

Will either of these options work? Opinions appreciated.

I have images for alternatives as well but will put in a subsequent post...

If a short ~1ft length of conduit from a rack-mounted junction box to a through-roof fitting like this can be directly supported by the junction box/through-roof fitting without requiring additional roof-mounted supports, this would be preferable to the fall-back option pictured earlier.

[Fafrd]

Found this which states Romex in the attic is OK for AC PV wiring: https://www.anapode.com/content/InstallACWiring

" AC Wire Type Choices

AC Wiring can be accomplished with a number of materials depending on situation and local code requirements. The most accepted method from the JBOX to the combiner or disconnect switch is 12AWG THHN (Stranded 12 gauge) copper in conduit. You can't really go wrong with that.

Some municipalities will allow single strands of hard 12 awg copper to be used but it's harder to pull through conduit.

Conduit isn't necessary if you're wiring inside the building so romex 12/3 may be allowed. This is the cheapest and easiest method.

There are also exterior rated cables that might be allowed without conduit but you should check with your township.

The basic message is that it's easy to ask the people who issue your building permit and follow their advice."

Any advice or opinion appreciated (including whether I can use an electrical junction to transition from Romex to rigid conduit under the soffit).

[inetdog]

Romex (TM), generically known as NM, is not allowed in wet areas. Under the NEC the inside of a conduit outside a building is also classified as a wet area.
So the NM has to stop at a box at the roof or wall penetration (or earlier) and either the trunk cable or THHN/THWN or similar wire used to reach that box.

[Fafrd]

Romex (TM), generically known as NM, is not allowed in wet areas. Under the NEC the inside of a conduit outside a building is also classified as a wet area.
So the NM has to stop at a box at the roof or wall penetration (or earlier) and either the trunk cable or THHN/THWN or similar wire used to reach that box.

Thanks for the reply. I think what you have written means NM/Romex is OK in through the attic as long I convert to different wire in a junction box just under the soffit, so that implies it is OK to have an electrical junction half way through the home run, correct?

And as far as the roof-side, if I go with a SolarDeck, I suppose I could make the electrical connection from the trunk cable to the NM/Romex there, correct?

Is stripping the jacket off of the NM/Romex to run through a short 1' length of conduit to reach a junction box on the rack an option, or are the wires within NM/Romex not allowed in exterior conduit even if the jacket has been stripped?

Thanks again for your help.

P.s. One last quick question - is it OK to run trunk cable into a Solardeck even if a short length of 3-6" is exposed from under the panel or alternatively, is it OK to position the Solardeck so it is partly under a panel and run trunk cable into it hidden by the panel?

[inetdog]

Is stripping the jacket off of the NM/Romex to run through a short 1' length of conduit to reach a junction box on the rack an option, or are the wires within NM/Romex not allowed in exterior conduit even if the jacket has been stripped?

Technically, under the NEC that is not allowed since the wires inside the NM are not normally marked as to insulation type.
So even if the wires were the equivalent of THWN, you could not use them that way without identifying markings supporting that.

[Fafrd]

Technically, under the NEC that is not allowed since the wires inside the NM are not normally marked as to insulation type.
So even if the wires were the equivalent of THWN, you could not use them that way without identifying markings supporting that.

Thanks. So I'll scrap that idea.

I spoke with the engineer at the place I am purchasing the components from (Renvu). He tells me that running the trunk cable into the Solardeck is fine, as is locating the Solardeck under a solar panel.

He also said that having an additional electrical junction under the soffit should be fine though the ground junction in both the Solardeck and the soffit junction will need to be 'irreversible' crimp connections.

My code states 10 AWG for up to 3840W so I am just trying to confirm that that applies to the ground conductor as well.

My system is 2250W based on Microinverter Max output (3kW based on max panel output) but I want to wire for a possible expansion to 3kW on this string (4kW based on max panel output).

I want to plan for a second string for up to 2250kW (3kW from panels), so I am now thinking:

Trunk cable to 3-conductor 10AWG NM within Solardeck (grounds crimped)

NM through to soffit in non-accessible attic

Junction box under soffit to transition from NM to 10AWG THWN (grounds crimped)

THWN in 3/4" metal conduit down to switch or 2-circuit Solar Load Center

Through the wall into the basement and into the subpanel (sized for at least 5760W if using a load center or 3840W if using switch.

Does this all sound like it should work?

[philips]

He also said that having an additional electrical junction under the soffit should be fine though the ground junction in both the Solardeck and the soffit junction will need to be 'irreversible' crimp connections.

From what I understand, the irreversible splice is for GEC connections, not EGC. If you are using enphase, they have a document showing how they do not require a GEC, so you may want to look into that and save yourself some trouble. This is how it worked out for my install and I specifically asked the AHJ in my area (El Cajon, CA). Of course, check with your AHJ as they may have a different interpretation.

[Fafrd]

From what I understand, the irreversible splice is for GEC connections, not EGC. If you are using enphase, they have a document showing how they do not require a GEC, so you may want to look into that and save yourself some trouble. This is how it worked out for my install and I specifically asked the AHJ in my area (El Cajon, CA). Of course, check with your AHJ as they may have a different interpretation.

Thanks.

Because I have 72-cell panels, I cannot use Enphase and am debating between NEP or APSystems dual Microinverters. I will check both to see whether they require GEC or only EGC.

Showing myself as a newbie, but woukd you mind to tell me what 'AHJ' stands for? I assume it is something to do with the local inspector for solar systems but don't understand the acronym...

[philips]

AHJ: Authority having jurisdiction - so local building department most of the time.

[Fafrd]

AHJ: Authority having jurisdiction - so local building department most of the time.

Got it - thanks .