Help with diagram of solar array

minisolar
minisolar Solar Expert Posts: 158 ✭✭
edited August 2021 in Solar Beginners Corner #1
Hey

I am in the final stages of planning my system and need help with the solar array planning. I am attaching my diagram - please let me know if anything is wrong.. wire gauge, breaker size, missing things, anything... 

4x 200ah 12v Renogy AGM = 24V 400ah
All in on mppsolar: 2400watt, 2000w max array, 150voc max, 80a mppt, 60a battery charger. 

https://www.ebay.com/itm/165003768538?hash=item266afdb2da:g:dGkAAOSwRyRbD5ik

Array...

I found a local seller so I can pick up: q.peak duo l-g8.3/bgt 420

They are $210 each.... I am thinking of getting 4 of them. 

Questions:

  • Can I hook up these 4 panels: make two parallel pairs then connect those two pairs in series which will keep me under 100voc? if yes: how do I go about hooking that up? 
  • I believe that for that mix I need a 30amp breaker between panels and mppt? 
  • Can anyone recommend appropriate breaker and breaker housing if needed? 
  • Since these are bifacial - I believe I have interesting options of mounting them? Anyone can give some advise on this? I am in upstate NY so I will have snow.. 
  • I will measure the distance next time I go but I think my distance is 50-75ft away from mppt. Can I run 10awg? 
  • Can I build mounting gear for panels myself? 
  • grounding - where and how? 





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Comments

  • wellbuilt
    wellbuilt Solar Expert Posts: 763 ✭✭✭✭
    Hmmmmm it’s strange no one has replied .?
    Out back  flex power one  with out back 3648 inverter fm80 charge controler  flex net  mate 16 gc215 battery’s 4425 Watts solar .
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    I can't really see what your breakers are, but they look like automotive stereo breakers.   They will cause you grief.  Get the Midnight Solar DC breakers and the mini-boxes to put them in.   https://www.solar-electric.com/marine-rv/array-combiner-boxes.html


    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • MichaelK
    MichaelK Registered Users Posts: 234 ✭✭✭
    Be careful who you purchase from.  I am hearing lots of stories about fake MPP units out there.
    System 1) 15 Renogy 300w + 4 250W Astronergy panels,  Midnight 200 CC, 8 Trojan L16 bat., Schneider XW6848 NA inverter, AC-Delco 6000w gen.
    System 2) 8 YingLi 250W panels, Midnight 200CC, three 8V Rolls batteries, Schneider Conext 4024 inverter (workshop)
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,036 ✭✭✭✭✭
    Two parallel strings of panels don't require any breakers/fusing. That being said you still may want the (Midnite) breakers for system maintenance.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Hi minisolar,

    Regarding the PV breaker and box,  MidNite boxes and breakers are really the best.  For DIN DC breakers use the BigBaby box,  or the Baby box:
    https://www.solar-electric.com/misobigbabox.html

    The baby box is tiny,  and a bit difficult to run cables,  no room for a negative busbar,  etc.

    DIN DC breaker:
    https://www.solar-electric.com/midnite-solar-mnepv-20-amps-circuit-breaker.html

    The exact breaker rating,  depends on the gauge of the cable feeding the PVs to the CC   ...  20A is minimum,  and perhaps a 30A and somewhat larger cable,  due to possible distance.  Place the PV breaker near the Inverter/Charger.

    Your PVs will probably have a Voc,  a bit above 100 V in cool/cold WX conditions,  with two of them in series,  but the solar charger appears to have a max rating,  near 150VDC   ...

    Midnite also sells Panel Mount breakers  --  MNEDC series,  that can mount in the Quad Box.  These breakers need crimped lugs,  whereas the MNEPV DIN breakers have screw terminals.

    FWIW,  Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    Thank you for the help. 

    I will get those midnight breakers and box for the array. Great info here Vic. 

    1. Any tips on mounting the bifacial in my weather where I will get snow? how high off the ground? Anyone built their own mounting system? Mine are going in a large clearing I have in the woods so I need to build something nice for them to be propped up. Since they are bifacial I believe they will greatly benefit from being higher in the air

    2. My AC circuit panel is grounded. But should I add any other grounding rods and connection anywhere? 

    3. Breaker for the battery bank. I wish to spend more and get the ones made by eaton (wind and sun sell them). But they only come in 150amp or 200amp. Bill recommended I put 170amp breaker. Can I use any of those 150/200 instead? which one will be safer/better? 



  • wellbuilt
    wellbuilt Solar Expert Posts: 763 ✭✭✭✭
    Hi mini ,  If you watt to try those panels , the front needs to be 4K of the ground and pitched to the sun .
      I’ve seen guys put white land scape rock under it . 
     If you get deep snow the panels should be up to compensate for it .
    Out back  flex power one  with out back 3648 inverter fm80 charge controler  flex net  mate 16 gc215 battery’s 4425 Watts solar .
  • wellbuilt
    wellbuilt Solar Expert Posts: 763 ✭✭✭✭
     You could get the fuses that I posted in the other thread at any amp you need . 
      Your system should only have one common ground for every thing . 
     I remove the ground screw in my Service panel and grounded every thing in my inverter panel . 
      
    Out back  flex power one  with out back 3648 inverter fm80 charge controler  flex net  mate 16 gc215 battery’s 4425 Watts solar .
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    Thank you Wellbuilt. 

    " I remove the ground screw in my Service panel and grounded every thing in my inverter panel" 

    I am not sure if I understand this. Can you explain to me again? 

    I currently have my circuit breaker box (ac loads obviously) grounded.... 

    I am just curious if I will need to also ground my battery bank / inverter/ solar panels... and if so - how and where? 

    Any help on this: Breaker for the battery bank. I wish to spend more and get the ones made by eaton (wind and sun sell them). But they only come in 150amp or 200amp. Bill recommended I put 170amp breaker. Can I use any of those 150/200 instead? which one will be safer/better? 

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    First, are you changing to a MPPT Solar LV2424 inverter-charger? If so, then you do need to review all of its specifications/requirement.

    Is this the unit you are looking at?

    https://www.mppsolar.com/v3/split-phase-lv/

    Looking around in Downloads, found the manual. Looks like there may be AC input current limit setting (max genset load in your case):

    http://www.mppsolar.com/manual/SPLIT PHASE LV/LV2424 hybrid manual-20190717.pdf

    For the "single point" Neutral+Ground bonding on the AC side--Just one location. If main panel or at the AC inverter or elsewhere--Just choose one (your Honda ec2000i is floating AC, so the N+G bond in the main AC panel should be fine for you).

    I have not looked through the manual in detail... Some things are assumed available like VAC / 60 Hz output for the LV2424 unit (not in the general manual section).

    And that the unit is 2,400 Watt max continuous output, the DC input current would be:
    • 2,400 Watts * 1/0.85 AC inverter eff * 1/21.0 volt battery cutoff = 134.5 Amps max continuous
    • 134.5 Amps * 1/0.80 NEC continuous current derating for breakers and branch circuit wiring = 168 Amp minimum suggested fuse/breaker/wiring on DC battery cable (if you plan on 2,400 Watt loads)
    https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

    And look at 1 AWG or 1/0 AWG wiring (depending if you want the 1/0.80 or 1.25x NEC derating for wiring and breakers @ 2,400 Watts.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    Sorry for the confusion Bill. This company, which sells many of these and has a U.S. rap that I spoke with, has many models and need a bit of work to find right manual - I did find the right one. I ordered it already - arriving next week

    http://www.mppsolar.com/manual/PIP-LV 110_120VAC/PIP-LV 3KVA manual-20210701.pdf

    For $699 you get an 2,400w inverter, battery charger, and mppt that can support up to 150 voc and 2000w of array for 24v... So I might actually break even on once I sell my12v parts. 

    It has a lot of setting options. It is on the manual. You can even limit the current from generator. Yes it does have 60Hz. you can set it to either 60Hz or 50Hz and to 110vac or 120vac. It has many settings

    But with this larger array I will be getting (4x420w bifacial) - I will probably not charge in the next few years since I won't use it in winter and even when I will use it in winter - bifacial seem to be perfect for winter with the ability to take power from the ground as well so snow will help it actually. but that is for down the road...

    I am hoping to also by the batteries next week and I hope to have all the other stuff figured out with you - wire sizing, ground, breakers location and types, and so on. 
    • Ground - not sure if I understood you - "N+G bond in the main AC panel should be fine for you" - so this is all I need? Or I need another one for mppt/array/inverter ? 
    • Then a 150amp breaker for bank will be good? 
    • 30amp midnight with baby box - is good for my array? (4x 420 watt panels in p&s connections
    • wow so this 2.4kw inverter bumps up my series and parallel wires as well as my wires between inverter and bank? if 1/0 is safer I will do that. I will order these premade and they are very short runs so it won't be that expensive. Can you please tell me sizing of the wires in my diagram since we have now have a larger inverter?
    • Bifacial solar mounting: angle? toward true south? since they are bifacial - should I mount them at a steeper angle since they will be able to take light from the back so if it snows the snow will slide off? 
    • Saw a video of a guy saying he needs to 'equalize batteries' before he connects them in parallel for 24v. Is that something I need to do as well? 
    I am very excited for this. Hoping to have the other items ordered next week 
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Hi minisolar,

    In Reply #7,  you said,  "3. Breaker for the battery bank. I wish to spend more and get the ones made by eaton (wind and sun sell them). But they only come in 150amp or 200amp. Bill recommended I put 170amp breaker. Can I use any of those 150/200 instead? which one will be safer/better?".

    What model are the Eaton breakers that you referred to?  The breaker between the Inverter to the batteries (and,  if there is a  provision for one, the breaker between the Solar charger, and the battery) should have particular specs,  for fire safety and reliability.

    For example,  the surface-mount breakers (which used to be Eaton Bussman,  and are now Cooper Bussman),  might not be your best choice,  verses the larger Magnetic Hydraulic breakers that need to (generally) be mounted inside metal boxes.  These breakers must be DC rated and should really have an interrupting capacity of 5,000 Amps,  minimum,  at the circuit voltage that you are using  ...   not to over-complicate things.  The large frame MidNite breakers ("E" and "F" frame ones that are 1 inch, and 1.5 inch wide),  are up to the task.  Perhaps some of the Schneider large frame breakers,  which are probably Square D brand,  are OK,  too.   These breakers would need to be mounted in some metal enclosure.

    Regarding the reference to the Baby box and MN breakers,   as littleharbor mentioned,  above,  two strings of PVs do not require a Combiner box for the PV array.   You will just need a breaker near the inverter charger,  to protect the cable that feeds the PV power,  into the solar charger portion of the inverter,  unless,  that inverter already has a disconnect/circuit protection,  built-in.

    A PV Combiner would be needed,  should you add any more strings (three,  or more strings of PVs),  however   ...

    You are asking good questions,  and it is clear that you wish to do this job well,  and for safety.

    Later,  Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    edited August 2021 #14
    Hey Vic, 

    Thank you for your help. 

    Yes I was referring that breaker - I thought Eaton made them for BUSSMAN:

    https://www.solar-electric.com/mrcb-150-amp-dc-circuit-breaker.html

    I believe the inverter I bought has an internal breaker but i also think the instructions said that you need one between pv and mppt. 

    Anyhow, please provide a link tot he breaker you recommend. I rather spend more and get something more failproof and safer... 




  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    edited August 2021 #15
    Hi minisolar,

    IMO,  the following breaker is up to the task:
    https://www.solar-electric.com/mnedc175.html

    There is a relatively smallish MidNite box,  the MNDC175,  or MNDC175Plus,  which includes the above breaker in a box,  with mounting locations for other breakers,  etc:
    https://www.solar-electric.com/search/?q=MNDC175PLUS

    This is considerably more expensive,  than using your favorite breaker,  which is easily,  surface-mounted.   This inexpensive breaker is a Thermal type,  has 3,000A interrupt capability at 24 V,  and has exposed battery voltage   ...   but it is common in the Marine market,  and they do work.

    The all-in-one inverter may have some of the breaker functions built-in,  that would have been mounted into the MNEDC box,  in the OLD days,  so maybe,  the Bussman breakers will do OK in your application.

    I do not want to drag you onto the road of increasing the expense of your system by quite a bit.

    Those Bussman breakers do work,  and probably are adequate for your job   ...

    Later,   Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    edited August 2021 #16
    Thank you Vic. 

    I found the other one you mentioned: https://www.stellavolta.com/Midnite-Solar-MNDC175-Mini-DC-Disconnect.htm

    So with the 30amp breaker I need for the PV I'm looking at about $220 Vs. about $90 for the two Bussman. Leaning toward the nice midnight....

    Question - if in a few years I decide to switch to lifepo4 (maybe a 300ah bank) then will the midnight 175amp breaker be adequate as well (assuming same or similar size inverter - not bigger for sure!)?

    Also on the topic of breakers: I currently have a 30amp on my diagram for the inverter ac feed into my breaker panel. Since I now bumped up to a 2400watt vs 2000watt inverter: Does this breaker also need to be bumped up? 

  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Hi minisolar,

    YES,  that Link is to the non-plussed MNDC 175.

    Regarding the 175 A breaker for future battery upgrades,   that breaker's main job,  is to protect the cables that connect to it,  battery interconnects,  etc.  If your upgrade needed to supply more than the 175 A rating,  the battery cables and the breaker would need to be changed.

     A 30 A AC breaker should be adequate for your 2400 watt inverter,  including reasonable surge,  IMO.

    Later,   Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    Perhaps this will clear my question - If I have the same inverter but instead of 400ah agm 24V I will have 300AH lifepo4 24V - will this breaker need to be changed?

    I have to say that I am very surprised at how hard it is to find a good guide online to size the interconnecting cables and cable between bank and  inverter.... 


  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Hi mini..,

    If,  when you upgrade,   you retain the proposed 2400 watt inverter,  that 175 A breaker should be fine.  BB Bill calculated,  pretty much the worst-case current flowing in that circuit.   These MidNite breakers are rated for continuous current at the rating of the breaker,  forever,  without tripping (essentially).

    The surge rating of that inverter is only for a short duration.  So,  if you retain the proposed inverter that IS 2400 watts continuous output,  you should be fine.

    The size of the battery cabling,  depends on its length,  current,  and maximum temperature rise of those cables.  The voltage drop at maximum current is often the dictating factor,  especially in 12 V systems,  and often,  in 24 V systems.

    There are NEC Ampacity Tables that offer guidance on minimum cable sizes,  for specific types of cable vs permitted temperature rise.   For our type of systems,  the maximum permitted temp rise is 75 degrees C   ...   assuming that you are in the USA/NA.

    Try very hard to keep the cable length between the batteries and the inverter at,  or less than five feet.

    There are voltage drop calculators that help one know if this is the dominant thing to consider.

    BB Bill has helped with the cable sizing  --  he said,  look at #1,  or 1/0 AWG,  for a well-designed system.

    Back to work,  here,   Later,   Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • wellbuilt
    wellbuilt Solar Expert Posts: 763 ✭✭✭✭
    As far as the cables go , I would get the largest cables that will fit in your inverter and charge controller   .
      When you get the equipment Figure out the type of ends and size wire you can fit on ports . 
     I use these cables .
     There is good info on the site allso , my  cables where ordered on Monday and came on Thursday.
    Out back  flex power one  with out back 3648 inverter fm80 charge controler  flex net  mate 16 gc215 battery’s 4425 Watts solar .
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Regarding inverter and battery interconnect cables,  why not check with the Sponsor of this fine Forum?   This way,  you will be certain to get cables that comply with NEC/UL standards,  with proper lugs for the stranding of the cable - an example:
    Inverter cables, red/black pair, #2/0 AWG, 5 foot | Northern Arizona Wind & Sun (solar-electric.com)

    Some vendors appear to focus on the automotive cable market.   The standards and needs for such cables are significantly different than those that we need.

    Often these cable vendors use SAE cable that is usually 5-15% smaller cross-section than AWG cable that we need for our systems.

    IMO,   FWIW,  etc,   Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    Bill recommends 1/0 which as far as I can tell - our sponsor does not offer. I will be happy to buy from our sponsor. 

    I one premade cables. I will not be crimping and doing all that on my own 


  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    minisolar said:
    Bill recommends 1/0 which as far as I can tell - our sponsor does not offer. I will be happy to buy from our sponsor. 

    I one premade cables. I will not be crimping and doing all that on my own 



    minisolar,

    Please ask Wind-Sun,  if they can supply 1/0,  terminated cables, configured as you need.   They used to have a very broad selection of cables,  that are suited for our power systems.

    Thanks,  Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    I will ask them

    I think I am very close to finishing up my plan. 

    Only major questions are:

    Do I need another ground rod beside the one I currently have for my AC breaker panel? 

    And is the 30amp breaker ok for my PV? 

    I am attaching my updated diagram. Let me know your thoughts please 


  • wellbuilt
    wellbuilt Solar Expert Posts: 763 ✭✭✭✭
    You can only have one ground rod that every thing hooks to , you can ground to water lines allso 
     as stated above you don’t need breakers for 2 strings of solar panels . 
      The breaker between the charge controller and the battery need a breaker that will protect the wire . 
    Out back  flex power one  with out back 3648 inverter fm80 charge controler  flex net  mate 16 gc215 battery’s 4425 Watts solar .
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭

    minisolar,

    As mentioned before,  "The exact breaker rating,  depends on the gauge of the cable feeding the PVs to the CC   ...  20A is minimum,  and perhaps a 30A and somewhat larger cable,  due to possible distance.  Place the PV breaker near the Inverter/Charger".

    You CAN use a 30 A DC-rated breaker for the PV input to your inverter/MPPT Solar charger,  so the minimum size of the cables for this run,  from the PVs would need to be #10 AWG,  minimum.

    You will really want a breaker for the PV input to your inverter,  for convenience,   AND,  for debugging,   plus,  often you will want to sequence the battery voltage,  and PV voltage application to the solar charging function of the inverter.   A DC disconnect would do this job,  but a circuit breaker will protect the cable,   AND provide this disconnect function for FREE.  Place this breaker,  near the inverter,  for convenience.

    Later,   Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    Yes the idea of having a breaker to be used as a disconnect is great and the reason I want to have them.

    I will measure distance this weekend so I know where my panels will be about to really make sure I can do 10 awg. 

    What I am still in the dark about is grounding... 

    What needs to be grounded and how.... 

    - I believe that I need to connect all my panels and their racking together using 6awg then run that to my ground bus in my midnite box.
    - connect a 6awg between my mpp solar ground screw (it will then ground both my inverter and my mppt since it is in the same unit) to the ground bus in midnite box
    - run a 6 awg from neg bat terminal to ground bus bar 
    - then run a 6awg from ground bus to my ground rod that has the ac panel connected to it... 

    Am I even close to being right? 

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    I would not run the Equipment Static ( frames & racks ) Ground into any electronic panel.  I think there is a code safe way to
    take the equipment ground ( lightning rod ! ) to it's own ground, and not bring it indoors to meet with the electronics.

    This sort of code confusion really hurts my head
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    mike95490 said:
    I would not run the Equipment Static ( frames & racks ) Ground into any electronic panel.  I think there is a code safe way to
    take the equipment ground ( lightning rod ! ) to it's own ground, and not bring it indoors to meet with the electronics.

    This sort of code confusion really hurts my head
    Like I said - I am hoping to get a definitive answer from this great forum about how to do it right. 

    My inverter/mppt, generator, dc midnite box, and batteries are all in the same location and about 30ft away from my cabin so driving another rod into the ground right next to them and hooking up all those to that rod is very easy... Is that the better way? 
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    edited October 2021 #30
    Grounding in general... If you have chances of lightning, then:
    • Run ground rod on outside of foundation... You do not want to bring lightning into the building. Lightning energy tends to want to go to the edges/outside walls of a building--Why, for example, not to mount a solar array on roof and run wires & ground down middle of building. The magnetic fields from lightning current flow forces current away from center of building
    • When grounding AC power systems, I think we have that covered. Single point Neutral + Ground bond typically in main AC panel. Float grounds in genset and AC inverter. Gets more complicated with shore power (boats, RVs)--May need switch to make/break ground bonding as needed (i.e., lift RV N&G bond when connected to shore power, make N&G bond when running from inverter or genset onboard RV).
    • Suggest that AC grounding wire(s) run to single ground rod (outside foundation). And ground battery bus negative to same ground rod (home power systems usually have 15-20 amp breakers and current flow on branch circuits---DC circuits to Inverter and such can have several hundred Amps--Need heavier ground wires so don't mix AC chassis and green wire grounds with DC chassis and green wire grounds. The single point where both meet keep you electrically safe, but (generally) keep High fault currents separate from lower (AC) fault currents.
    • Lightning strikes are "high frequency" events and do not follow current paths for DC and low frequency (60 Hz) AC current paths. For example, if you have a solar array--Ground frames and racks together and run grounding wire (suggest 6 AWG minimum for all safety grounds to ground rods) straight down to ground rod outside of foundation at base of structure (short, "soft bends" and NO right angles--Lighting will "leave" at right angles). The ground rod per metal structure (and things like local ground for pump house and such) take care of lightning. All ground rods (related to central power system like genset, inverter, grid power, etc.) should also be tied together with 6 AWG cable between all ground rods. This is to protect against DC and 60 Hz AC short circuits. Say you have a 120 VAC flood light on your remote solar panel structure--If there is a short from 120 VAC hot to structure--The current through to the ground rod may not be enough to trip the 15 amp breaker back at the inverter/genset/main panel). A "good ground" rod to earth connection can be as high as 25 Ohms (120v/25ohms=4.8 amps). 4.8 amps is not enough to trip the breaker and will leave the structure energized (i.e., somebody touches structure and wet grass--gets electrocuted). Tying the remote ground rod back to the home ground rod/grounding system provides a current path to "fault" the breaker if there is a short. GFI breakers/outlets will also help reduce the chances of electrocution.
    Grounding provides two (major) tasks. 1. to trip the branch circuit breaker in case of a short from hot to chassis/green wire ground. And 2. to direct lighting away from the home and protect occupants from lightning energy. Using Surge Protectors at "wall" of building (where solar wiring enters building, telephone lines, satellite dish wiring, etc.) will help limit damage from nearby strikes, AC main panel Hot and Neutral wiring helps limit the spread of lightning surges/damage. A direct strike will usually take out most electronics so accept that as a cost of modern living:

    https://www.solar-electric.com/search/?q=midnite+surge

    Lightning will only follow (something like 6 AWG cable) for a few 10's of feet before it "finds" a better path. Take to ground rod as close as practical. There are woven cables that have lower impedance and work better for lightning protection of structures (used in the USA south lands where lightning is a common problem).
    Re: Working Thread for Solar Beginner Post/FAQ

    A couple threads about Lightning:

    Off Grid Grounding Technique?
    Another Question, this time about Lightning

    Note, the above are discussions, not a do A, B, and C--and you will be "safe". There probably is no such thing with lightning. Several different techniques are discussed--and a few of those posters even have experience with lightning. :cool:

    And our host's FAQ:

    https://www.solar-electric.com/learning-center/solar-system-lightning-protection.html/ (link updated 9/30/2020 -Bill B.)

    From other past posts here, Windsun (admin/owner of NAWS), he said that most of lighting induced failures he saw were in the Inverters' AC output section.

    Towards the end of this thread is a very nice discussion of proper generator grounding.

    -Bill

    12/5/2020--How to measure soil resistance (in 50 pages):

    https://www.weschler.com/reference/guides/practical-guide-to-earth-resistance-testing/

    Multipoint grounding solution for Florida AM radio stations and lightning:

    https://www.copper.org/publications/pub_list/pdf/a6189-wtmn.pdf
    https://www.radioworld.com/tech-and-gear/new-grounding-system-ensures-radio-broadcast-stations-remain-on-the-air

    HAM Radio Grounding presentation:

    https://w4bfb.org/wordpress/wp-content/uploads/presentations/GroundingPresentation.pdf

    Lightning and lightning control:

    https://www.w5nor.org/presentations/PolyphaserGuide.pdf
    For driving ground rods--There are adapters to impact drills/demolition hammers that make it much easier than hand driving a rod:

    https://www.homedepot.com/p/TR-Industrial-3-4-in-Steel-Ground-Rod-Driver-for-TR-100-and-TR-300-Series-Demolition-Hammers-TR89107/306721757 (example of adapter--Different electric hammers need different shanks)

    And there are "ground plates" that can be buried in shallow soil (common issue in mountainous areas):

    https://www.kuefler-lightning.com/product-category/grounding-rods-plates-chemical-ground-rods-and-clamps/

    I am not saying to do anything that violates NEC... But NEC has historically not been very strong on lightning control issues.

    As an example, one "retired" electrical/solar design engineer member here--The last 10+ foot run from remote solar array to home--He used a outdoor electrical cord and plug... When lightning was forecast, he would disconnect the cord and pull it away from his home (Florida).

    Some other random thoughts...

    The shunt used for Current/Battery Monitor System... The side that connects to the battery bus--Only connect to batteries... No other wiring on that side. The "load side" of the shunt is were everything else is connected. You want all loads (discharging and charging currents) to flow through the shunt so you can monitor battery state of charge.

    The solar array wiring is very specific to the array configuration you are using. If you start out "small" and add on later, you have the choice of wiring for "small array" and later removing (or upgrading) existing wiring for new array. Just a cost of solar arrays (when you get to 3 or more parallel panels, you need a "combiner box" with breakers (or fuses) to protect each string from a short circuit being fed by the rest of the array--Check panel specifications for series fuse rating--Typically 15-20 amps).

    Fire: Assume anything not metal can burn. Any exposed cable (insulated to batteries as an example) should be mounted on a non-flammable surface. And anything under such "dripping combustibles" should be non-flammable too (sheet metal, concrete backer board, ceramic tile, etc.). With enough energy (arcs, current flow, etc.) any plastics can be burned.

    Use appropriately rated wiring. UV resistant for solar arrays, Wet for underground conduit. Direct burial rated, etc.... And I like to run "large" diameter "conduit" (OK, I am cheap, I use black ABS pipe--Not legal) to allow changes and upgrades later as the system and power needs grow. In theory, if you have "mixed" wiring (say genset 120/240 VAC wiring, and 12 VDC remote on/off wiring)--The wiring should be in separate conduits between home and outbuildings (you don't mix "high voltage power" with low voltage signal circuits).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    edited October 2021 #31
    Sorry for vanishing but Hurricane Ida flooded our house and I had to deal with the aftermath. The little time I had needed to be spent on finishing our cabin's bathroom since it is getting cold and curing will be an issue for thin-set and grout... I finished it last weekend. 

    Hoping to finally get this finalized and built. I will go over Bill's notes about grounding.