Stand Alone Solar Arc-fault protection devices.

FilterGuy

What, me worry?
As I was reading the rapid shutdown requirement in the 2020 NEC, this jumped out at me:

690.12(B)(2)(3):
PV arrays shall have no exposed wiring methods or conductive parts and be installed more than 2.5m (8 ft) from exposed grounded conductive parts or ground.

If I am reading it correctly, I think the first part essentially says that the wiring has to be in conduit.

I am having a hard time parsing the second part. If you ground the PV Array frames.... how do you meet the requirement to be "installed more than 2.5m (8 ft) from exposed grounded conductive parts or ground."
 

mrzed001

Voice of reason
Like I said "A lot of equipment" to meet the requirements. It used to be that the panels were by far the cost driver of a system. Now it is all the other equipment driving the costs.

Yep. An optimizer for SolarEdge costs half the price the panel it is attached to.
OK I think they overprice it "a bit" since there is no real competition in this area.

Tigo can be used with Growatt hybrid I think (does Growatt even have an AFCI ? Donno).
But full off-grid I can not say that I know any working solution.

Also there is 3 type of arcing:
- serial : 1 cable damaged and arc is on it
- parallel : arc between the 2 cables
- ground : 1 cable to ground arc
To check for all 3 ... heavy.
 
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daklein

New Member
there is 3 type of arcing:
- serial : 1 cable damaged and arc is on it
- parallel : arc between the 2 cables
- ground : 1 cable to ground arc
To check for all 3 ... heavy.
PVAF-T says it detects multiple types of arc faults, and up to the system controller to act appropriately. Serial is most common, but parallel or fault to ground could occur. How would one act on the system to stop each different arc type? serial, turn off the charge controller or inverter, or open one side of the PV. parallel, short circuit across PV +/- fault to ground: hmm, clamp both to ground?
 

daklein

New Member
Midnight and outback both make multi-pole ground fault breakers:
Thanks, I wasn't aware of the Outback ones. These multi-pole breakers look similar between Outback and Midnite, different amp ratings and number of pole. They have a .5A breaker paralleled to trip them or detect ground fault.

Reading the manual and AFCI app note for Outback's FM100 AFCI charge controller is interesting. Sadly, more complicated systems are required for DC charge controller or string inverters. I wonder if any of them do more than just mitigate for series arc fault? I guess disabling each PV module separately will also stop parallel of arc to ground. I guess that is an actual advantage of a 2019 NEC compliant system vs. 2014,2017.
https://www.outbackpower.com/downlo...ollers/flexmax_100_afci/fm100_afci_manual.pdf
 
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Hedges

I See Electromagnetic Fields!
Wow.... I just looked it up and your right. That is tough requirement to meet without a lot of equipment if you are using a long string of panels.... It kinda drives toward micro-inverters and 'just' shutting off the AC so the Micro-inverter shuts off.


Make you wonder who was lobbying for this. People who like laws, and people who like sausages ...

I previously saw a 4-panel unit. Here's a 2-panel, so $30/panel.


Would take 4 of those to support one of my 8 x 36V panel strings.
 

OffGridInTheCity

Solar Addict
I have Midnite Classic charge controllers - which have 'arc-fault' built-in. I believe its detecting PV array wiring arc-faults - e.g. trying to alert you that you might have a 'bad connection' in your PV array. It also has DC ground fault (which I understand is similar to AC GCIF). Here's som excerpts from the Midnite Classic user's manaul:
1622923537449.png
1622923711731.png
 
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FilterGuy

What, me worry?
It also has DC ground fault (which I understand is similar to AC GCIF).
Only loosely related.
AC GFCI is a shock prevention requirement that trips ate ~7ma. DC Solar Ground Fault Protection is a fire prevention requirement that trips as high as 1 Amp. Furthermore, the devices and how they operate are *very* different between AC and DC.


There are a growing list of NEC requirements on solar mounted on your home.
  • Arc Fault Protection (Fire prevention)
  • Ground Fault Protection (Fire Prevention)
  • Disconnect requirements (Shock prevention)
  • Rapid Disconnect (Fire Fighter shock prevention)
  • Wire size requirements (Fire Prevention)
  • Fusing Requirements. (Fire Prevention)

Understanding and meeting all of the requirements is not easy and certainly not cheap... particularly since for most of the requirements you must used 'listed' devices.
 

400bird

Solar Enthusiast
Oh, this is an older thread, but has anyone seen a reasonable priced solution to AFC/NEC 690.11?

I was looking to add an MPPT charge controller to my Schneider XW 6848.
But the only Arc Fault Detection I have seen is included in $700 rapid shut down boxes, such as the Schneider MPPT Disconnect RS and I believe something more expensive from Outback.
 
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