diy solar

diy solar

Stand Alone Solar Arc-fault protection devices.

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 said:
All panels get an own optimizer.
Click to expand...
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.
 
FilterGuy said:
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.
Click to expand...

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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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.
Click to expand...
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?
 
FilterGuy said:
Midnight and outback both make multi-pole ground fault breakers:
thepowerstore.com

Outback PV Ground-Fault Detector Interrupter 80 Amp 150Vdc single pole panel mount (SKU Part Number PNL-GFDI-80)

PV Ground-Fault Detector Interrupter 80 Amp 150Vdc single pole panel mount Information Ground fault detection and interruption is required by the NEC as a safety precaution. The OutBack PV Ground-Fault Detection and Interruption System protects wiring an
thepowerstore.com thepowerstore.com
Click to expand...
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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FilterGuy said:
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.
Click to expand...


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.

Tigo TS4 Rapid Shutdown Solutions

The TS4 platform from Tigo allows for several different solutions for module level rapid shutdown. Complies with NEC 2014, 2017, and 2020 rapid shutdown requirements.
www.altestore.com www.altestore.com

Would take 4 of those to support one of my 8 x 36V panel strings.
 
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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OffGridInTheCity said:
It also has DC ground fault (which I understand is similar to AC GCIF).
Click to expand...
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.
 
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.
 
Interesting and somewhat depressing thread. All these requirements mean well but make it more expensive and difficult to go off grid.
My new build will require 100% compliance with all the requirements in the NEC. I hope more of the AIO will have these protections built in soon.
Just been told of further delays in our plans....going to be a 3 year process to build the way it is going :mad:
 
I'm pretty sure my Solar Edge grid tie PV inverter does have arc fault built in. I believe many do, considering it is required.

My issue was with the charge controller. I've got a Schneider battery inverter, but their charge controllers do not have arc fault protection done internally.
 
Quattrohead said:
Interesting and somewhat depressing thread. All these requirements mean well but make it more expensive and difficult to go off grid.
My new build will require 100% compliance with all the requirements in the NEC. I hope more of the AIO will have these protections built in soon.
Just been told of further delays in our plans....going to be a 3 year process to build the way it is going :mad:
Click to expand...
Midnite Classic charge controllers have Arc Fault and you can set the sensativity.
Agree that all of this is pretty big $ but my perspective has changed over 3 years of operation. I now have 45 panels in 3 groups of 3s5p - and IF a ban connection were to start, arc fault might help diagnose - maybe 10yrs in or 20yrs in... and I can appreciate having it.
 
Another bump.

Wondering how to address arc fault and ground fault.

Midnite has both ground fault and arc fault. There’s a white paper on the ground fault. Make sense.

Does anyone know how the Midnite classic arc fault system works. I’ve been up and down the website and manual and don’t see it. Specifically, can it signal any panel level device? Like the Tigo optimizer?

Or a SMA Sunspec module level shutdown device? Or the Apsmart?

SunSpec Certified Rapid Shutdown Technology | SMA America

Each PV system is unique. Different roof structures, system alignments and various types of shading influence the PV system's energy yield. Thanks to the innovative TS4-R module technology, energy yields can be increased.
www.sma-america.com www.sma-america.com

Though, if I understand it correctly (unlikely), the Sunny Island/Midnite Classic combo might get you to arc and ground faults with the sunspec added.
 
Both ground-fault and arc-fault simply direct MPPT to cease drawing current (or could open the circuit.)

Only RSD "Rapid Shut Down" needs panel level device.

Ground-fault of PV is often something like a 1A fuse from PV (-) to ground. Inverter (in the case of GT PV) monitors voltage of PV (-). If a short occurs anywhere else, current flow through fuse, fuse blows, PV (-) changes in voltage, inverter detects that and shuts off.

(unlike AC ground-fault a.k.a. residual current circuit breaker)

Arc-fault has to analyze AC signal in wire, distinguish bad signals from good signals, then shut off current flow.
 
I think Bluedog225's point is that both systems (arc fault and ground fault) shut off the load. Neither cuts power at the source, like opening an RSD, that seems required to create actual safety.
 
You may achieve safety by cutting off the load. You're left with PV string shorted to ground at some point, but both ends open circuit.
Or in the case of arc-fault, a poor series contact, but no current through it.
That leaves system in a relatively safe state.

However, two shorts would have current running through ground. Arcs to ground, if in two places or one plus a short, could continue to arc. So two faults could mean it remains hazardous. Probably responding quickly to first fault avoids that.

RSD drops voltage between any two wires < 80V. At that, could sustain an arc so not perfect. But in practice, the products do something like 1V per panel, 25V for a string (in the case of Solar Edge.)

It's all a matter of just how safe it can be made, how rare a catastrophic failure. (or how financially disadvantageous it can be made.)
There are real issues - WalMart had half a dozen stores torched by Solar City PV systems.
 
I'm going to have to admit I never thought to deeply on the actual arc an AFD was detecting.

I hadn't realized the arc fault was for poor series connections. I had assumed it was an arc to ground, but that's why there is GFD!
I'm embarrassed, I should have thought through this at some point.
 
I have Midnite Classics and I've had my Arc Fault trip. It stops incoming PV. The idea is that it can detect a bad/loose connection in the PV wiring that is 'arcing' and stops allowing load (stops current flow) so the arc doesn't burn something up. Gives you a chance to find the issue/fix.
1644039295070.png
Arc Fault has sensitivity settings and in my case I didn't have an arc but made it 1 level less sensitive.
The user manual says:
1644039517055.png
1644039562721.png
1644039490594.png


Midnite Classic Ground Fault is a DC version of GFCI in AC - and I believe it shuts off output amps (and therefore input amps).
This is the section from the user manual:
1644039635361.png
 
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