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GlennWest

Ground fault breaker for solar

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Searched and found no mention on here. I know it is mandated on stick and brick. Would it be a good idea on our units?  Been studying up on inverters and came across this.

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My 2000W inverter has the GFCI built into the 120 volt outlet. I connected the hard wire circuit to not be on the GFCI. It is wise to have GFCI on 120V ac. It is regulation in most building codes for some areas. Like near water or outside. 

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Glenn, as you already know a typical RV has built in GFCI receptacles (or downstream protection thereafter) especially near kitchen or bathroom sinks and of course outside receptacles. If they sense as little a 0.005 to 0.006 amps of fault current they are designed to trip. They still function if you're on Genset or Inverter power provided all is complete and wired correctly.

Now let me put on my old n rusty power engineers hat and lay a bit of info on you in case you weren't already aware.

When plugged to home or RV pedestal shore power the AC secondary distribution system has its Neutral bonded to a proper adequate Grounding Electrode such as a "made electrode" like a copper rod driven into the earth. Therefore, the voltage of a 120 VAC leg with respect to mother earth (which is bonded to Neutral) is 120 volts and if say an RV skin/frame was hot electrified and your barefoot grandson standing in water touched the RV (or any hot leg) you better hope the GFCI works to save his life..........

However, even though many Gensets as well as Inverters utilize a Bonded (NG Bond) versus a Floating Neutral, there's no hard wired dedicated low impedance bond (rubber tires offer a resistance to mother earth) from Neutral to a proper Grounding Electrode (such as earth). That means "in theory" you could be standing barefoot on the ground and touch the RV's hot skin or a hot inverter or genset leg and not be electrocuted. Of course, there's still a "resistive" path to the earth on which the RV sits SO DONT TRY THAT !!!!!!!!!!!!!

Obviously even if fed by a Generator or Inverter if you get between 120 volts you can die dead and a GFCI can prevent that SO STILL USE THEM EVEN IF ON UTILITY OR GENSET OR INVERTER POWER !!!!!!!!!!!!!!!!!!! I would still use the GFCI receptacles in an RV especially if they serve outdoor receptacles, better safe then sorry.

New home construction now requires AFCI protection in addition to GFCI but Im unaware of any RVIA or NEC requirements in RV's. I see no reason why they cant be used and they do provide protection.   

PS YOU ASKED GROUND FAULT BREAKER FOR SOLAR ???? Solar Power is derived from DC solar  panels feeding solar charge controllers having DC output to charge DC batteries. Its the Inverters that produce AC for which GFCI could play a role 

DISCLAIMER Im longggggggggggg retired from power distribution and rusty as an old nail and NOT up to date on NEC or RVIA or any other codes so this may be right it may be wrong. I still believe it to be accurate, its my best recollection but don't risk your life on it...

I would leave the RV's GFCI's in place....

John T

 

Edited by oldjohnt

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I'm asking about DC. I had never even considered this but according to Midnite Solar it is now mandatory on dwellings to have this breaker coming out of solar controller to battery. It is a MNDC-GF breaker. Now I personally don't see the need. It is for the "protection" if the solar array shorts out.

Edited by GlennWest

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A solar panel disconnect is required on residences it's so the Fire Department can shut off the power coming down from the panels before they start fighting a fire.  Usually the first thing they do is yank the electric meter so the grid power is off but in a solar installation the panels (and inverter) can still energize the building's wiring.  Hot wires aren't a good idea when you're spraying water and swinging fire axes inside a burning building.

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I did a Google search for MNDC-GF breakers, the first hit was Midnite Solar's own page. Under the "Documents" tag, there's a "Manual" link to a PDF drawing, stating the 2008 NEC first required these breakers. The accompanying drawing shows a ground mounted solar array, with the breaker in question installed between the array and the charge controller. They also show separate, not linked, breakers inline, between the controller output and the batteries.

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2 hours ago, GlennWest said:

I'm asking about DC.

Thanks for the update Glenn, now that you say  you're "asking about DC" I have additional likewise updated information......Based on your initial "Ground Fault" language I gave you advice that "Ground Fault" Circuit Protection could still work and should still be used EVEN WITH Inverters you also spoke of, and that still remains true in my opinion..

Even thought you first mentioned "GROUND FAULT" BREAKER above and also mentioned Inverters,  it appears you are now only concerned with  DC and BREAKERS,  so here's my updated information...

Assuming you mean "Breaker" NOT "Ground Fault Breaker", even if there were no NEC or RVIA requirements for such, AS AN ENGINEER I HAVE ON MY OWN SYSTEM AND PREFER (at least an On Off disconnect means even if NOT an overcurrent protection device) A DISCONNECT METHOD so I can shut off the solar panels PV INPUT to my charge controller..........

As I posted previously, if the manufacturer   OR  any codes require one be used DO IT period, you don't want to void any warranties. As I also stated before "some" gentlemen do NOT install overcurrent protection circuit breakers UP ON THE RV ROOFTOP (before entry down to charge controller) believing since a circuit breaker has to be able to pass the max charging current and since a solar panel (unlike a battery) has such a relatively low limited Short Circuit output capacity THE BREAKER MAY NEVER TRIP.

BOTTOM LINE  1) If the manufacturer ORRRRRRRRRR or any codes require an overcurrent protection device  OR   a disconnect method between panels and controller input  BY ALL MEANS USE IT

                           2) I personally recommend at least an On Off disconnect means (sure an overcurrent protection breaker will suffice) so I can turn off and disconnect the solar panels PV INPUT to my charge controller.  And I would do that even if there were no Code or manufacturers requirements for my own safety, peace of mind, and especially CONVENIENCE. I sure have one  

SIMILAR AND LIKEWISE if the manufacturer OR any codes ALSO REQUIRE a Breaker "coming out of the solar controller to battery" as you stated YES INDEED INSTALL ONE

NOTE IN ADDITION to protect the cables FROM battery TO the charge controllers DC charging output, on or near the battery AN OVERCURRENT PROTECTION DEVICE IS REQUIRED TO PROTECT THE CABLES . Therefore you may have to use two , one right at the controllers DC charging output (if code or vendor required)  PLUS of course one to protect the cables located at the battery...........     

 Thanks for clarifying and updating Glenn, hope this helps. Again, if the manufacturer OR codes require it at EITHER the controllers PV INPUT or  the controllers DC charging OUTPUT      JUST DO IT lol 

John T

Edited by oldjohnt

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Glen,

Residential solar is very different from RV solar (typically).  Residential solar controllers typically convert the DC power generated from the panels directly into AC power that is fed back into the grid.  In this case a GFCI breaker would be necessary and would be 120 volt (or possibly 240 volt depending on the solar controller output).

On an RV, the solar controller is DC to DC and is simply charging the battery bank.  There should be a breaker between the battery and the solar controller to protect the controller and the wiring, but it would be a standard DC breaker of the appropriate rating.  It is also handy to use as a switch to isolate the batteries from the solar controller.

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In our area there are different types of residential solar systems.

Those (some Amish or remote cabin owners) who are total OFF GRID use batteries to store energy and the batteries supply power to their Inverters for their AC needs.

Those where the utility permits use GRID TIE  in which case Inverters change the incoming DC to AC that's synced with the utility grid and NO batteries are used to store energy.

The Off Grid and battery energy storage is, of course, more like what an RV uses. Once power comes out of an Inverter GFCI can of course still be used. Any type of system can use Overcurrent Protection and/or On Off Disconnects for safety and convenience and ESPECIALLY if the manufacturer or any codes require it. Even if NOT required I recommend a disconnect method to shut off my solar panels PV output to the charge controller input, and, of course, the wiring from batteries to a charge controllers charging output needs overcurrent protection   

Congratulations Glenn, nice system you're building

John T

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My solar would send at most 20 volts dc to the controller and battery. I am not concerned with GFCI on that. Some solar panels are operating at 100's of volts. That would be a problem needing GFCI.

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49 minutes ago, GlennWest said:

Mine will be around 100 volts to controller.

Glenn, FWIW I think that (100 volts) represents a reasonable configuration and number (mines over 70 volts typically) even if a solar charge controller might accept up to 150 volts. Again, while a disconnect means and overcurrent protection is okay on the PV DC input side of a charge controller, any GFCI (if required) comes AFTER  an Inverters AC output and that's well covered above.

Remember you promised I could park next to you and plug into your system lol you can power your own Zipcode

John T

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I looked at that thing by Midnite. It is meant for house, roof top, earth referenced systems. I don't see what good it could do on a RV.  With a RV or trailer, there is no "ground" reference for it's operation. We do have to be careful with higher voltage dc,  but I don't think this devise will help. Maybe John could look. Midnite site;  https://www.solar-electric.com/mndc-gfp.html

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Glenn and Sehc, okay here are my thoughts regarding the Midnite unit. I apologize and admit I had to educate myself regarding Ground Fault Protection on DC Solar systems AND IN MY COMMENTS ABOVE I was ONLY speaking about traditional GFCI in AC systems of which an Inverter or a Generator still applies. I was NOT discussing DC Ground Fault above yet my AC system GFCI comments still apply  

1) It is now my opinion YES  DC GFI since 2008 IS REQUIRED in "HOME" solar systems regardless if rooftop OR ground mounted.

2) I have NO IDEA if they are required in RV Solar systems ??????????????????????????? FWIW  I understand Sehc's comment doubting if they are required in an RV BECAUSE there, UNLIKE a home system, there is no reference with respect to mother earth. In  home power distribution into which a solar system may be combined (even if sure batteries and Inverters etc may be buffers) THERE IS A DIRECT QUALITY LOW IMPEDANCE BOND AND REFERENCE TO MOTHER EARTH as the Utility Neutral is tied to earth and if configured as a "Separate Derived Source", a Generator and Inverter would also have their Neutral tied to mother earth............HOWEVER in an RV neither the Batteries nor the Inverter nor the RV frame nor the solar panels or generator ARE BONDED TO MOTHER EARTH anywhere near how a home system is..

3) As I now understand it the reason the NEC started requiring GFI in """Home""" Solar Systems (which has a bond to earth) is if there was DC fault current  flowing from the PV DC circuit to earth IT COULD BE A FIRE HAZARD.  THEREFORE the GFI if it senses 1/2 amp of current flow to earth (it needs a grounding electrode such as a driven rod or perhaps it uses the distribution system earth ground) it trips and opens the panels DC circuit, preventing a potential fire hazard

THAT ALL BEING SAID   I still DO NOT KNOW if DC GFI is required in """"RV"""" Solar Systems by the NEC or RVIA. I DO KNOW its required in """"HOME"""" solar since 2008 BUT a home system has a bond to earth and the NEC is concerned about current from a shorted or faulty HOME Solar DC circuit  to earth might be a fire hazard.

Soooooooooooo even if its NOT required for an RV ????????? even if it may not help or function to sense 1/2 amp of fault current to earth because an RV isnt bonded to earth as well as an approved Grounding Electrode in a home system,,,,,,,,,,,,,,,,,,I DONT SEE IT WOULD HURT anything but I don't understand (as of now I may later lol)  how its the same as in a GROUNDED system... How can there be a 1/2 amp flow to EARTH  and how could it be measured ESPECIALLY since the RV when driving or dry camping IS NOT TIED TO A GROUND ROD ????

NOTE if hooked to an RV pedestal then yes the RV frame ISSSSSSSSS bonded to the equipment Ground THIS IS DIFFERENT from dry camping or driving !!!!!!!!!!!!

   Best I have to offer NO WARRANTY its right. IFFFFFFFFF the NEC or RVIA requires DC GFI in an RV I advise its use. Hey just because I dont see how its the same in an ungrounded RV (NOT like a home system earth ground) dont mean it ain't so............IF THE NEC OR RVIA REQUIRES IT   DO IT PERIOD.......... 

PS after thought. I guess if the RV frame is configured as "ground" albeit NOT a bond to earth, and since the solar power should flow through the + and - conductors NOT a frame member, if a solar conductor shorted to frame that's in a sense a GROUND FAULT which a DC GFI could sense and shut down ??????   Darn if I know     

John T  BSEE,JD Longggggggggggggggg retired n rusty power distribution engineer so nooooooooo warranty lol

Edited by oldjohnt

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Thanks John and the rest. I know it caught my interest when on their site. Actually getting an E Panel and they go deep into that discussion in the manual. I am like the rest of you, what benefit in an rv. Thanks again for the education.

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I think you get to teach us Glenn!  It's mobile and it is over 60V DC, would it need to fall under automotive high voltage rules?  Orange cables (or convelute), servicing disconnect connector, HVIL high voltage interrupt loop (does that apply to an only two item 'loop'?), tagged cut loops, etc, etc.  Do ya wear your linesman's gloves or do ya put trashbags over the panels?  Buy these parts out of the Leaf too?  Be very careful putting that part together! Google the hell out of it!

Some automotive stuff to think about:

https://ncdoi.com/OSFM/RPD/PT/Documents/Coursework/EV_SafetyTraining/EV EFG Classroom Edition.pdf

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As John said this may not apply whenever the RV is functioning without an earth ground ??? but what about when hooked up.  When hooked up there is an earth ground back through the main panel.  Is this something we need to be concerned with?  There is also a note that the battery neg should not be grounded to the earth with this.  That would not be easy in an RV.  When RV solar systems were relatively small this probably didn't matter much but I don't know if this applies in the larger and larger systems some of us are installing.  Our system is 12v based but it is 2,000 watts, less than half of Glenn's great solar, but the panels are rated a little over 60v.  Enough to at least sting and maybe more under the right conditions and certainly enough power to start a fire.  Scrap's comments also caught my attention. Glenn may have highlighted something that needs more study and information and it may not have obvious answers.

 

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This is getting to the point were going to have to let Glenn sort it out and decide. I don't see the product harming anything so if he chooses to use it (even if NOT NEC required) that's his decision regardless whatever any of us think.   While I may be able to form a better opinion if I had the time to thoroughly research the NEC that's really getting deep in the weeds and I'm rusty on that stuff.

However I can say this based on years or experience and practice and compliance with the NEC and attending numerous of their training seminars over the years IF THEY SAY TO USE IT YOU CAN BET ITS BASED ON THE BEST AVAILABLE SCIENCE AND BY EXPERTS FOR GOOD REASON. I remember so many times at a seminar asking why in the world is some section required when I see no reason why it should be I LEARNED WHY LOL

As we all seem to agree above an RV based DC Solar System with its onboard panels and controllers and Inverters when dry camping NOT connected to shore power WITH NO BONDING OF THE NEUTRAL TO MOTHER EARTH,,,   IS DIFFERENT FROM CONNECTION TO THE UTILITY  WHERE THE NEUTRAL IS BONDED TO MOTHER EARTH............ 

Here's a question if anyone knows the answer ??? If in a home solar system the DC GFI breakers are monitoring for a leak to "ground"  if you're in an RV dry camped, to what or where is is that fault current leaking ???????????  The RV frame ???? Fault current requires a current path to somewhere !!!!!!!!!!

"Ground Fault" when in an RV isn't the same as "Ground Fault" when hooked to an earth grounded power distribution system. I understand the ground fault concept I described above when the NEC requires it in case there's current flow from a panel to "ground"  as that could create a fire hazard but in an RV   I JUST DON'T KNOW IF ITS REQUIRED but as above just because I don't understand it DONT MEAN IT AINT TRUE LOL 

Good luck Glenn do what you think is best and ifffffffffff its required do it for sure DO NOT BASE YOUR DECISION ON ANYTHING I MIGHT SAY

John T  Too Longggggggggggggg retired from this stuff but hey I try my best

 

Edited by oldjohnt

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Wild and crazy frontier of mobile solar power. I'm glad I only have 400 watts. It is a fun project.

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11 hours ago, Randyretired said:

As John said this may not apply whenever the RV is functioning without an earth ground ??? but what about when hooked up.  When hooked up there is an earth ground back through the main panel.  Is this something we need to be concerned with?  There is also a note that the battery neg should not be grounded to the earth with this.  That would not be easy in an RV.  When RV solar systems were relatively small this probably didn't matter much but I don't know if this applies in the larger and larger systems some of us are installing.  Our system is 12v based but it is 2,000 watts, less than half of Glenn's great solar, but the panels are rated a little over 60v.  Enough to at least sting and maybe more under the right conditions and certainly enough power to start a fire.  Scrap's comments also caught my attention. Glenn may have highlighted something that needs more study and information and it may not have obvious answers.

 

Well we can't get away from battery grounding to frame. Would have to rewire entire DC side. We could put ground lug on chassis and carry rod with wire around. But that another item to forget and pull out. 

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1 hour ago, GlennWest said:

Well we can't get away from battery grounding to frame.

Glenn, That's one reason somewhere above I posed the question that perhaps a DC GFI would use the frame as ground for reference and measurement of "fault current" in the absence of mother earth???? The solar panel current flow should take place in its two + and -  conductors.

Just thinking, sorry no answers

John T

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The requirement of isolating the battery ground from the frame and earth ground when hooked up would seem to be an insurmountable obstacle.   That alone would make me look for another way to meet my goal. Isolating the ground has it's own safety issues.

Edited by Randyretired

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