FAQ: Residential roof installation requirements for the USA

[x98myers7]

Hi Everyone. as a part of my residential install research, I have spent weeks working to understand the laws/requirements for solar panel installations on the roof of an occupied dwelling (ie; a home) in the United States. Bottom line-- you need to have a listed solution to all of these requirements to be in compliance. Good luck! Hopefully this list will help with your research.


Also, please keep in mind... this list is not exhaustive; just the major ones that are the hardest to comply with.


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Primary NEC requirements - NEC 690 Solar Photovolatic (PV) Systems
NEC 690 is your "law" however your local jurisdiction has final say; Authority Having Jurisdiction "AHJ" as most people reference it here on the forum. On a state-by-state basis, you need to determine what NEC version you comply to. If you stick with the latest requirements, you're probably most in compliance.

Check here:

NEC® Adoption List

here's the 2017 version of the NEC

70-17SB-PDF.pdf

Shared with Dropbox

www.dropbox.com

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Arc-Fault Circuit Interruption (AFCI) -- 690.11
PV systems operating at 80V dc or greater between any two conductors must be protected by a listed PV arc-fault circuit interrupter or other component listed to provide equivalent protection.

Relevant links

How to Comply w/NEC 2017 690.11 Arc-Fault Circuit Proection (DC)-Strings > 3 Modules?

How to Comply w/NEC 2017 690.11 Arc-Fault Circuit Proection (DC)-Strings > 3 Modules? Is there any DC Arc-Fault protection equipment currently available that can satisfy the requirements of NEC 2017 690.11 for PV source and output circuits with over three 60 cell PV modules in series? If "no"...

forums.mikeholt.com

NEC2017 - AFCI exception for non-building systems

NEC2017's 690.11 section now has an exception to not require AFCI on ground-mount systems, provided certain conditions are met. The system & its wiring are not on or in a building The wiring is either Direct buried In a metal raceway In an enclosed metal cable tray This exception seems to...

forums.mikeholt.com

note:
To my knowledge, there is no standalone listed AFCI solution available. The UL approved options are all integrated in the SCC/Inverter/All-in-one unit, and/or employed with a micro-inverter based system. I would strongly advise you do NOT implement any SCC that does not support arc-fault detection and interruption from the factory. This is a critical safety feature and you can't add it on later.


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Rapid Shutdown (RSD) -- 690.12

PV system circuits installed on or in buildings shall include a rapid shutdown function that controls specific conductors in accordance with 690.12(1) through (5) as follows.

1. More than 5′ inside a building, or more than 10’ from a PV array
2. Controlled conductors shall be limited to not more than 30V and 240 volt-amperes within 10 seconds of rapid shutdown initiation
3. Voltage and power shall be measured between any two conductors and between any conductor and ground.
4. The rapid shutdown initiation methods shall be labeled in accordance with 690.56(B).
5. Equipment that performs the rapid shutdown shall be listed and identified.

NEC 690.12 Rapid Shutdown of PV Systems on Buildings - Inverters | altE

Since its start in 2014, the NEC requirement 690.12 for rapid shutdown of PV inverters has undergone changes in 2017 and 2020. Stay up to date here.

www.altestore.com

NEC 2020 Rapid Shutdown Requirements — Mayfield Renewables

Section 690.12 of the 2020 National Electrical Code (NEC 2020) covers rapid shutdown requirements and represents a vitally important safety requirement for solar PV systems.

www.mayfield.energy

Note:
To my knowledge both Tigo and IMO FireRaptor do offer RSD systems that can be installed in a standalone fashion and both are UL listed


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Ground Fault Protection -- 690.5
Grounded dc PV arrays shall be provided with dc ground-fault protection meeting the requirements of 690.5(a) through (c) to reduce fire hazards. Ungrounded dc PV arrays shall comply with 690.35

(a)Ground-fault detection and interruption
the ground fault protection device or system shall:
1. be capable of detecting a ground fault in the PV array dc current-carrying conductors and components include any intentinoally grounded connectors
2. interrupt the flow of fault current
3. provide an indication of the fault
4. be listed for providing PV ground fault protection

helpful

Ground Fault Protection On Solar Panel Arrays.

To get the paper, click on the orange button at the top of the screen. This paper provides a summary of what a PV ground fault is, what NEC requires for PV Ground Fault Protection and how PV ground Fault Protection is typically implemented...

diysolarforum.com

Note:
Ground-fault protection can be met by installing a UL listed DC ground-fault breaker. Something like a Midnite solar MNDC-GFP63

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PV Disconnect -- 690.1

PV Disconnect Placement per NEC 2017 Article 690.1 — Mayfield Renewables

Engineers, designers, installers, and manufacturers need to stay on top of jurisdictional code changes to ensure their products and systems will operate safely. Local regulations will vary, but there is perhaps no code more important to photovoltaic (PV) manufacturers, designers, and installers...

www.mayfield.energy

NEC 2017 690.1 & PV Disconnect Placement - Avila Solar Drafting

In 2017, Article 690 of the National Electric Code (NEC) was updated, which tells solar designers, engineers, and installers how to ensure that a PV (solar

avilasolar.com

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Overcurrent Protection 690.6(d)
The output circuits of ac modules shall be permitted to have overcurrent protection and conductor sizing in accordance with 240.5(b)(2)


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UL listed equipment
Basically, you have to use all UL listed equipment. Yes, that means even the roof brackets and rail system.


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Conductor Sizing 690.8(b)

690.8(B) Conductor sizing

Let me start out by saying I DO NOT LIKE REVIEWING SOLAR! Now that I got that off my chest, The issue I have is off a string the current, per the micro-inverter optimizer is 15A. There are 3 strings going from a combiner box to the inverter with 6 #10. Per 690.8(B) if I choose option 1, I...

forums.mikeholt.com

NEC 690.8: Any experts out there?

Folks, I have spent the last several days wandering through the labyrinth called the NEC trying to determine exactly what it says for solar panel wiring. I have learned a lot about the code requirements but there is one thing that one of you might be able to help me with. NEC 2017 excerpts...

diysolarforum.com

pro-tip... wiring Temperature Derating
-- If you're running wire in an attic or other heated space, you need to accommodate for temperature correction.

10/2 MC armorlite in attic DC from roof box to disconnect -- attic temp derating?

hi everyone, so, working on continued planning and trying to nail down wiring from my roof junction box to PV disconnect near the inverter. i'm in michigan. NEC approved flexible MC armorlite a while ago for attic use. yay --...

diysolarforum.com

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Panel Setback On the Roof
- panel spacing and placement for edges, valleys and gables

link relevant to CSC, International Building Code and NEC 2017 requirements

6.20.18 Firecode and Smarter Inverters

Shared with Dropbox

www.dropbox.com

"Use the 3ft Rule"

Know your codes for solar mounting

By Dan Felix, IronRidge training manager In the realm of solar mounting, codes are “alive” in that they are constantly being updated to keep pace with an

www.solarpowerworldonline.com

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Flashing and Rail Systems

Flashing must be installed for all roof penetrations and roof brackets must be screwed directly to roof trusses

note:
There are listed/UL approved systems for feet, flashing and rails. ironridge.com is the "standard" as of writing this

EJansen suggested a very new listed solution from Snap-n-Rack that appears to be exceptionally promising -- https://snapnrack.com/products/speedseal/

 

[ncsolarelectric]

FYI: The Tigo, FireRaptor, and HRSD devices that turn off the solar panels to less than 80V at the panels, do not discharge the DC capacitors of the inverter they are connected to. To my knowledge, ONLY the Sol-Ark inverters have a PV contactor to disconnect the PV wires at the inverter, to de-energize them when the shutdown is initiated. As one person recently found out, on the EG4 inverter, the capacitors do not discharge to < 30V in 10 seconds. It takes many minutes! Therefore, additional equipment in the form of DC contactors or DC SSRs are required at the inverter to disconnect the PV wires at the inverter end, in order to comply with NEC 690.12.
My advice is, if you're doing an off-grid system with one of these inverters, use a ground mount, and don't put the panels on a building.

 

[iamrich]

UL listed equipment
Basically, you have to use all UL listed equipment. Yes, that means even the roof brackets and rail system.

"listed and identified" does not mention UL. Ultimately you will be dealing with your city/county and power provider (if you need grid) to approve, but as written, UL is not the only listing body that will satisfy.

 

[EJansen]

Flashing and Rail Systems

Flashing must be installed for all roof penetrations and roof brackets must be screwed directly to roof trusses

note:
There are listed/UL approved systems for feet, flashing and rails. ironridge.com is the "standard" as of writing this

Snap-n-Rack provides a system that's UL listed that doesn't require directly screwing to roof trusses or using flashing with their new 'deck feet'. I used them on my recent DIY install of the arrays on the back of my garage, and so far so good. No leaks or missing panels and I've had some pretty wild storms to test it in the past couple of months.

 

[Bl2yan]

Snap-n-Rack provides a system that's UL listed that doesn't require directly screwing to roof trusses or using flashing with their new 'deck feet'. I used them on my recent DIY install of the arrays on the back of my garage, and so far so good. No leaks or missing panels and I've had some pretty wild storms to test it in the past couple of months to test it.

View attachment 108950

I see listing requirements mentioned often. A friendly reminder that engineering is a critical step in the construction process. A product can be UL listed but not be able to withstand wind loads of 110mph which may be required in your area. Similarly, a UL listed 3/16 toggle bolt can't hold/provide seismic for a 150lb inverter.

 

[ruralsolar]

So I'm running into this with the quoting process and I realize the answer might be "fuzzy" depending on jurisdictions, BUT, does a ground mount require a rapid shutdown system? The inverter at the moment is planned to be "inside" the home....

 

[ncsolarelectric]

So I'm running into this with the quoting process and I realize the answer might be "fuzzy" depending on jurisdictions, BUT, does a ground mount require a rapid shutdown system? The inverter at the moment is planned to be "inside" the home....

No, only solar panels on a building.

 

[Mike 134]

Just an FYI about the 3' setback rule for your solar panels. Some, and I want to emphasize that, and not all, do not allow the overhang to be part of that 3' pathway for firefighters.
For example, a gable roof with 18" overhang would need a 4'-6" pathway along that edge in some jurisdictions. Fortunately, mine did not.

 

[ruralsolar]

No, only solar panels on a building.

So even though wiring carrying the voltage from the panels is entering the building. I feel like the NEC wording is open to interpretation, common sense says full agreement, no need for rapid shutdown on not-building mounted panels but the words to me are a little more vauge.

 

[ncsolarelectric]

So even though wiring carrying the voltage from the panels is entering the building. I feel like the NEC wording is open to interpretation, common sense says full agreement, no need for rapid shutdown on not-building mounted panels but the words to me are a little more vauge.

The DC wires entering the building need to be in metallic conduit all the way to the metallic box of the inverter. Totally fireproof. RSD is not required. RSD is required when the "solar panels" are on the building.

 

[Danke]

Just an FYI about the 3' setback rule for your solar panels. Some, and I want to emphasize that, and not all, do not allow the overhang to be part of that 3' pathway for firefighters.
For example, a gable roof with 18" overhang would need a 4'-6" pathway along that edge in some jurisdictions. Fortunately, mine did not.

I have a flat roof and according to the NEC I need a perimeter. But my local AHJ doesn’t require it...

 

[ruralsolar]

Thanks All! I had reached out to a couple companies for DIY ready quotes which included permitting and plan design help, I'm finding that even on my own I can shave off ~6k by piece mealing myself, might be the route I'll go, will make another post with my idea there.

 

[Jirzlee]

Great thread, thanks to x98myers7 for putting this together.

So how many DIYers are building fully to NEC 2017 code for systems that don't have a grid interconnection agreement?

I was considering the EG4 18kpv (among others) - it doesn't meet code without some sort of separately purchased remote initiator switch plus devices at every panel which then cut the power, right? The DC power from the array needs to be reduced everywhere outside a 1 foot boundary from each roof mounted array if I'm understanding correctly. Plus, each module has to be dropped since "conductors within the boundary must be reduced to no more than 80V".

All this time watching videos and learning about solar installations and there's been hardly a peep about it. Its usually just a string inverter and a DC panel string and talking about VOC and whatnot. Is it just that most don't have them permitted/inspected so they don't bother?

Plus, I'm reading now about the RSD systems cutting power from the panels if the grid goes down. I'd assume that's an option on what devices you use and/or how they are setup?