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PV Combiners => Disconnecting Combiner Discussion => Topic started by: ligwyd on February 16, 2019, 12:59:19 PM

Title: Stand Alone Solar System in 20' shipping container - Arc Fault/ Rapid Shutdown??
Post by: ligwyd on February 16, 2019, 12:59:19 PM
Hello there,

Anyone know why Schneider does not make their Charge Controllers Arc Fault Compliant? I believe Midnite Solar's charge controllers have Arc Fault Protection built in. Also, have you guys done any conversions to existing systems to incorporate Rapid Shutdown after a project has already been completed.............. (ya I know.... why am I working in reverse :)

Just had the first walk through with my Electrician who may be pulling the permit for my project and then eventual inspection once everything is good to go.

My system does have a MNPV6-Disco mounted on the shipping container. I would think this would suffice for PV "rapid shut down". Not sure yet if I need rapid shut down for the battery bank and generator? I would think so since the batteries and Generator can still send power to the home.

Not sure yet but think my best bet and most cost effective may be to remove my two Schneider MPPT 60-150's and install two Midnite MPPTS of the same to have the system Arc Fault compliant. Then may have to remove my Midnite Discos and install a combiner/ disco than can accommodate rapid shut down and then install further install rapid shutdown/ wiring components in all other appropriate places.

We'll see what the electrician comes up with after hes went over the solar section of the code book....

Wish there was an easier way to accomplish this but don't think there is. Living and learning (and paying for it) :)

Any words of wisdom appreciated.
Title: Re: Stand Alone Solar System in 20' shipping container - Arc Fault/ Rapid Shutdown??
Post by: bee88man on February 17, 2019, 12:21:13 PM
Thought rapid-shutdown was for firemen to get safely onto a residintial roof with solar panels...your panels are on a container...no???
Title: Re: Stand Alone Solar System in 20' shipping container - Arc Fault/ Rapid Shutdown??
Post by: ligwyd on February 17, 2019, 01:46:18 PM
Yes, the panels are mounted on an aluminum array on top of the shipping container. I am hoping the inspector will pass it without rapid shut down since the panels are not on a roof and the shipping container is stand alone about 100 feet or so from the home.
May be the same with the Arc Fault requirement. I'll know more soon and will post the outcome.
I still would like to know more about Arc Fault products that can be installed on completed systems. I am sure there is high quality solutions out there just that I am not aware of them yet. Any info from anyone is appreciated. I heard from another Forum of a device called "Fire Raptor" but have been unable to find it yet.
Although both rapid shut-down and arc fault equip has it place and is critical, in many applications, I am hoping that it is not necessary on my systems. We'll see......
Appreciate the feed back. :)
Title: Re: Stand Alone Solar System in 20' shipping container - Arc Fault/ Rapid Shutdown??
Post by: tecnodave on March 07, 2019, 02:14:40 PM
Ligwyd,

I do not beleive that you need a rapid shutdown unless your array is on the roof of a dwelling. A container is not a dwelling unless you have done the engineering to certify that container as a dwelling, not even possible in most jurisdictions.  I have skirted the code by having my solar gear not on my dwelling but on an 40 foot shipping container. My building inspector is not happy with that but when I had my local Cal Fire inspectors review my systems, they were happy with it and squelched the building authorities.

My house "plugs in" to the solar system!    Very clearly in the National Electrical Code. " beyond the outlet is not part of the power system"......that has never been contested successfully.

Our (Santa Cruz County) building department is so far out of whack that they charged a local couple more than $70,000 in permit fees to upgrade a 70 year old existing building to a tiny studio apartment for the inlaws!  That was before the first turn of the shovel!

David
Title: Re: Stand Alone Solar System in 20' shipping container - Arc Fault/ Rapid Shutdown??
Post by: daklein on March 01, 2020, 12:57:00 AM

I still would like to know more about Arc Fault products that can be installed on completed systems. I am sure there is high quality solutions out there just that I am not aware of them yet. Any info from anyone is appreciated.

I am wondering about this question now, and I found this device, some on ebay for only $20, Sensata PVAF-T:   https://www.sensata.com/products/power-controls/pvaf-t-series-arc-fault-detection-solar-applications         

This is only a detector, it would need to signal a remote trippable breaker or switch to disconnect the pos PV line to the inverter  (stopping a series arc fault).  Maybe even better would be to then also close a switch to short the PV + - lines together (stopping a parallel arc fault).   

The solution of using an inverter or charge controller with integrated AF detection would be the best choice.   But, I have this low cost Classic 250-CP (without AF detection), that I'd like to make use of.   And, I have a remote trip switch capable of interrupting the PV before or after the combiner.

Related question to Arc Fault detection;  do the integrated solutions typically address both series and parallel arc faults?   Do they simply shut off, and stop drawing current from the PV, which would stop a series arc fault.   Or do they also short the PV leads to prevent a possible parallel arc fault?
Title: Re: Stand Alone Solar System in 20' shipping container - Arc Fault/ Rapid Shutdown??
Post by: daklein on March 01, 2020, 01:10:37 AM
Related question to Arc Fault detection;  do the integrated solutions typically address both series and parallel arc faults?   Do they simply shut off, and stop drawing current from the PV, which would stop a series arc fault.   Or do they also short the PV leads to prevent a possible parallel arc fault?

Found the answer (Thanks Robin!)    http://midniteftp.com/forum/index.php?topic=443.msg2612#msg2612
" If you have the MidNite Classic charge controller, you already have arc fault protection from series arcs. "   

So that leads to another question:
The device would have to detect if it's a series arc fault or parallel?   Or would trial and error work:  First open the PV circuit (stop drawing power from it, which will stop a series arc), and if the arc signature continues, then crowbar short the +- together to stop the apparently parallel fault?        The NEC requirements must be to handle both types of arc faults?
Title: Re: Stand Alone Solar System in 20' shipping container - Arc Fault/ Rapid Shutdown??
Post by: daklein on March 01, 2020, 01:29:46 AM
So that leads to another question:

   From the Sensata's PVAF-T data sheet.  It doesn't tell the difference, the rest of the system would have to handle figuring out which it is.

As described in UL1699B Edition 2 (2013), there are two types of UL
1699B recognition: Type 1 and Type 2. UL 1699B Type 1 recognition
requires that the arc fault detector (AFD) detect a class of series faults.
It also allows that the AFD may detect a class of parallel faults. UL
1699B Type 2 recognition requires detection of both a class of series
and a class of parallel faults. Neither Type 1 nor Type 2 recognized AFD’s
are required to distinguish between parallel or series faults. UL 1699B
only requires that the AFD detect an arc of 300 W or more in conditions
defined in the standard.
Sensata’s PVAF-T AFD has UL 1699B Type 1 recognition only. As such,
it detects a class of series faults. The PVAF-T also detects a class of
parallel faults, but it does not distinguish whether a specific fault is
a series or parallel fault. System designers using the PVAF-T should
incorporate appropriate system responses for both series and parallel
faults in their designs. System designers should also read the UL 1699B
standard to fully understand the differences and capabilities of Type
1 and Type 2 AFD’s before designing an arc fault interruption system
including any UL 1699B recognized AFD.



Title: Re: Stand Alone Solar System in 20' shipping container - Arc Fault/ Rapid Shutdown??
Post by: boB on March 01, 2020, 01:29:42 PM

The arc current has to share a path with the sensor and where it is placed of course.  That is typically where either the plus or minus PV wire comes into the inverter or charge controller.  So series arc can be shut down with a series switch to stop the arc current.

If the arc is inside of the PV array, between a positive and negative wire, that could be considered a parallel arc.

We actually had a solution for parallel arcs several years ago and Sandia labs was interested in checking it out.  Here is a paper related to that when we went down to Albuerque, NM at the time....

https://energy.sandia.gov/wp-content/gallery/uploads/SAND2013-5916-SeriesAndParallelArc-FaultCircuitInterrupterTests1.pdf

But only series arcs, which would be more common I think, are required to be dealt with.

Arc detection and protection does work but it can cause false trips and be annoying when it does.

boB
Title: Re: Stand Alone Solar System in 20' shipping container - Arc Fault/ Rapid Shutdown??
Post by: daklein on March 04, 2020, 06:54:06 PM
Thanks boB,   that's a very good read.