Change in 2023 NEC code around PV arc fault.

[FilterGuy]

I was working on a design and came across an 'interesting' change around PV arc fault protection in the 2023 NEC. In the 2020 code, you could have PV circuits going to your house without arc fault protection if the circuits were in metallic raceways (Conduits), In the 2023 code they seem to have removed that possibility.

This is one more thing that will make it difficult to do a code-compliant install with any of the value-priced inverters that do not have arc fault built in.

NEC 2020 Code 690.11


NEC 2023 Code 690.11

 

[fafrd]

I was working on a design and came across an 'interesting' change around PV arc fault protection in the 2023 NEC. In the 2020 code, you could have PV circuits going to your house without arc fault protection if the circuits were in metallic raceways (Conduits), In the 2023 code they seem to have removed that possibility.

This is one more thing that will make it difficult to do a code-compliant install with any of the value-priced inverters that do not have arc fault built in.

NEC 2020 Code 690.11
View attachment 137389

NEC 2023 Code 690.11
View attachment 137390

Is this an inherent advantage of Microinverters over string inverters?

 

[FilterGuy]

Is this an inherent advantage of Microinverters over string inverters?

Oh yes! The microinverters take care of several PITA NEC requirements:

• Rapid Shut Down
• Ground Fault Protection
• Arc Fault Protection
• PV Disconnect

This is why solar installers love micro inverters here in the US. I have been asked by a lot of people about bids they got on solar and in the past year or two they have been 100% EnPhase microinverters paired with panels.

 

[zanydroid]

It’s all because of the microinverter cabal. Err, I mean Enphase. I wonder how Enphase will adjust their business model once residential solar incentives / ROI goes down to the point where turnkey $3+/W installations stop making financial sense…

I thought most of the recent string inverter designs had GFP and Arc Fault, but they are awkward to retrofit onto older designs.

 

[Hedges]

Sounds like inverter without arc-fault can't be on the house, rather on a post next to the hose. Then AC can enter the house.
Any value priced inverters that are rain tight (like newer SolArk?)

Whatever happened to 3rd party Arc-Fault? Did I buy the last two Sensata units in existence?

 

[SeaGal]

I was working on a design and came across an 'interesting' change around PV arc fault protection in the 2023 NEC. In the 2020 code, you could have PV circuits going to your house without arc fault protection if the circuits were in metallic raceways (Conduits),

Sorry if I'm having a blonde moment, but doesn't the 2020 reg already state that the exception is only "For PV systems not installed in or on buildings"?

It looks to me that they have just reworded the exception to make it clearer, without actually changing the regs

 

[ChrisG]

Wouldn’t a midnite classic CC cover this scenario. Believe it solves for Ground and Arc fault.

 

[Hedges]

Sorry if I'm having a blonde moment, but doesn't the 2020 reg already state that the exception is only "For PV systems not installed in or on buildings"?

It looks to me that they have just reworded the exception to make it clearer, without actually changing the regs

I read 2020 to say exceptions are:
1) Systems not installed on buildings
-or-
2) Wires in metal raceways
-or-
3) Underground wires (i.e. PVC OK underground)

Note the comma (,) after "PV systems not installed in buildings", which I take from the way rest of sentence is written to be part of an enumerated list, rather than followed by conditions for such systems.

But, the first word "For" does seem to indicate balance of comma delaminated clauses all refer to things not on buildings. Or, is "For" implied to be repeated after each comma.

Does this paragraph actually mean that if you have MC wire between PV panels, not metal conduit (or metal armored cable) going between PV junction boxes, then arc-fault is required? Even though on a detached structure, not considered to be a building (per this paragraph.)

Old men sit around a table listening to themselves talk. They may not think through what the words they write down mean.
The 2023 version is explicit, and may reflect what at least some of the old men previously interpreted 2020 as saying.

 

[SeaGal]

Yes, interesting...

My reading of it is that the 2020 and 2023 are the same. But, because of the bad grammar in the 2020 edition, it has been made clearer for the 2023 edition.

IMHO I read 2020 to say exceptions are:
1) For systems that are not installed in or on buildings then
1a) exemption if wires in conduit OR
1b) exemption if wires in metal raceways OR
1c) exemption if wires are underground
2) The term building does not include a dedicated building used solely for PV, but would apply for buildings used for other things such as house / garage / office / workshop etc.

But... I'm British YMMV.

If it _were_ an enumerated list and you then remove some of the entries of that list, you would be left with the sentence
"For PV systems not installed in or on buildings shall be permitted without arc-fault protection". This makes no sense with the word "For" at the beginning.

There is (to me) a poor use of commas in the regs, especially before the "or"s. It's like it has be written by a 10 year old before teacher told the class that you don't just put in a comma at the point where you would breath. Hence, why I suspect the regs remain the same, but are now written clearer.

 

[400bird]

There's two ways to interpret the 2020 arc fault requirement. Guess which way my AHJ interprets it?

Yes, now I've got a very nice Midnite Classic charge controller with arc fault detection integrated.

 

[Hedges]

My reading of it is that the 2020 and 2023 are the same. But, because of the bad grammar in the 2020 edition, it has been made clearer for the 2023 edition.

IMHO I read 2020 to say exceptions are:
1) For systems that are not installed in or on buildings then
1a) exemption if wires in conduit OR
1b) exemption if wires in metal raceways OR
1c) exemption if wires are underground

Doesn't that mean, if you have PV panels mounted (anywhere, even ground mounts with inverter hanging there too) with plastic insulated MC cables between them (as is standard), then arc-fault is required? Because there are wires not in a metal conduit?

Of course what we wanted was to simply be allowed to use metal conduit/raceway for DC wires in or on a dwelling, and put the PV array on ground mounts or a dedicated structure. Then not have to use AFCI.

 

[SeaGal]

Doesn't that mean, if you have PV panels mounted (anywhere, even ground mounts with inverter hanging there too) with plastic insulated MC cables between them (as is standard), then arc-fault is required? Because there are wires not in a metal conduit?

I read it that it depends on where the dc circuit goes. If the dc is not in or on a building (like your example of ground mount panels with inverter there too), then pvc insulation is OK. Just can't have PVC insulation of dc without arc-fault detection if that dc goes in or on a (non-solar-dedicated) building.

Of course what we wanted was to simply be allowed to use metal conduit/raceway for DC wires in or on a dwelling, and put the PV array on ground mounts or a dedicated structure. Then not have to use AFCI.

That sounds permissible the way I read it from both sets of regs.

 

[Hedges]

I read it that it depends on where the dc circuit goes. If the dc is not in or on a building (like your example of ground mount panels with inverter there too), then pvc insulation is OK. Just can't have PVC insulation of dc without arc-fault detection if that dc goes in or on a (non-solar-dedicated) building.

But I read your interpretation as saying if not on buildings, only wire in metal raceway or underground avoided arc-fault requirement.
Therefore, if MC cables between panels, arc-fault still required.

I presented this to show such an interpretation would be absurd (not to say that is not what the words might mean.)

That sounds permissible the way I read it from both sets of regs.

We think not. If PV array on ground mount and DC wires in metal conduit from array to inverter either on outside wall or inside house, because DC circuits are "in or on a building", arc-fault is required per NEC 2023.

So I see it as saying conversion from DC to AC must occur on a non-building structure. Maybe rigid conduit pops up out of the ground one foot away from house, hybrid inverter is mounted on that conduit, AC (and possibly battery DC) enters house.

 

[Hedges]

So when does NEC 2023 get adopted in California, and when in less significant markets?

 

[reader2580]

So when does NEC 2023 get adopted in California, and when in less significant markets?

California has their own electrical code based on the NEC. They are currently on California electrical code 2022 which is based on the 2020 NEC. I would guess California probably won't have a code based on the 2023 NEC until 2025.

Minnesota generally adopts the new code on July 1st of the year of the code. For example, the 2017 NEC was adopted on July 1, 2017. The 2020 NEC was adopted on Nov 17, 2020 due to the pandemic. I assume the 2023 NEC will be adopted on July 1, 2023.

 

[rhino]

What exactly is the definition of an arc-fault in relation to a PV array?

 

[rhino]

Yes, now I've got a very nice Midnite Classic charge controller with arc fault detection integrated.

It may detect it but how does it address the issue if there is an arc-fault? If the DC circuits are arcing somewhere between the Midnite Classic and the array you'd still need something else to actual stop the arc.

 

[Tecnodave]

It may detect it but how does it address the issue if there is an arc-fault? If the DC circuits are arcing somewhere between the Midnite Classic and the array you'd still need something else to actual stop the arc.

Arc fault does shut down the system as is required by the code, It interrupts the current flow and eliminates the arc fault by opening the circuit that is faulting and reduces the faulted circuit to zero amps......ARC FAULT INTERRUPTED

And YES....The Midnignt Classic does come with built in Arc Fault as well as Ground fault except for a few scaled down models that are not equipped with arc fault and ground fault due to those who value money over safety

 

[FilterGuy]

What exactly is the definition of an arc-fault in relation to a PV array?

There are two types of arc fault.

1) Serial Arc Fault. This is most common when a connection is loose. This is also the type of fault the PV Arc Fault protection is required to stop.
(A PV array has a LOT of connections both between the panels and within a panel). This type of arc can be stopped by opening the circuit and stopping the current.)

2) Parallel Arc Fault. This is an arc that forms between the positive and negative legs of the PV circuit and is far less common in PV arrays.
This type of fault is harder to stop unless you have a system that can disconnect the conductors someplace between the panels and the Arc.
Also, note that this type of arc fault is a type of short circuit. Depending on where it occurs, a parallel arc fault could blow the string fuses and stop the fault. If the parallel arc is between a PV line and ground, the NEC-required ground fault protection should trigger and at least isolate the fault from the rest of the system.

Both types of arc faults require a sophisticated evaluation of the 'noise' an arc creates on the line. The system needs to be able to distinguish an arc fault from a 'normal' arc that can occur when a switch is thrown. Some of the systems that have arc-fault are too sensitive and have a lot of false triggers.... prompting people to disable the function and live without it.

 

[Shimmy]

FWIW, the intent of the 2020 code (and by my read the 2023 code, but equally poorly written) is to requrire the PV wiring *within the occupied structure* to be in metal conduit or raceways. The handbook makes it pretty clear:

...The exception allows PV output circuits on ground-mounted PV systems, meeting the requirements, and those installed in metal raceway and metal clad cables, to be installed without arc-fault protection.

I kind of get the logic.

 

[rhino]

So why is it so hard to get a device that we can add that is rated to at least 500V DC and will stop the series arc fault? If Midnite is including this in their charge controller there surely is some way to have at least a separate device to do the equivalent functionality.

 

[cs1234]

Just keep your solar voltage below 80v.

 

[FilterGuy]

So why is it so hard to get a device that we can add that is rated to at least 500V DC and will stop the series arc fault? If Midnite is including this in their charge controller there surely is some way to have at least a separate device to do the equivalent functionality.

Good Question. I have been wondering about this for a long time.

Stand Alone Solar Arc-fault protection devices.

I have been studying the NEC requirements for wiring solar panels and one of the requirements is arc-fault protection if the PV array is at 80V or more. However, when I search for PV arc-fault protection product.... I find no stand-alone products. Some SSRs have it built in. Most grid-tie...

diysolarforum.com

My hypothesis is that there is not a large enough demand. In the US, the vast majority of the professionally installed systems that require NEC compliance are done with Micro-inverters that keep the PV voltage under 80V, so there is no need. The new professionally installed systems that don't use Micro-inverters use string inverters with it built-in or high-end battery systems with it built in. Meanwhile, some chunk of the DIY market is done with inverters that have it built in (Such as SolArc). My guess is the rest of the DIY market is done without compliance or inspection so it does not create a demand for an arc-fault product.

I don't know what the requirements are outside of the US, but my impression is the Arc Fault requirements are not as stringent outside the US.

This leaves the stand-alone arc fault device market as a tiny niche that no company has decided to go after.

Having said that, if one of the value-priced inverter companies would release a product that had Arc Fault and Ground Fault protection built in, I think it would be a big hit in the DIY community as long as it did not jack up the prices much.

 

[rhino]

So just looking at this in more detail this was very interesting research on PV arc faults: https://www.analog.com/en/technical-articles/arc-detection-analysis-for-solar-applications.html

Edit: TI even has block diagram with parts on how to create one https://www.ti.com/solution/solar-arc-protection

 

[400bird]

California has their own electrical code based on the NEC. They are currently on California electrical code 2022 which is based on the 2020 NEC. I would guess California probably won't have a code based on the 2023 NEC until 2025.

Minnesota generally adopts the new code on July 1st of the year of the code. For example, the 2017 NEC was adopted on July 1, 2017. The 2020 NEC was adopted on Nov 17, 2020 due to the pandemic. I assume the 2023 NEC will be adopted on July 1, 2023.

And people think California is strick with regulations ?
We're at least 2 years behind. Because after the state writes CEC 2025(or whatever) it also needs to be adopted by the local AHJ, there might be a specified timeline for that, but it still adds time.