Wiring the bank

2

Comments

  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank
    vtmaps wrote: »
    I....I've lost track of the bonding situation. Where are your neutral-ground bonds? Are you breaking the bond in the generator?

    Also, to economize you could have a ground bus bar at the solar room and have a single run to the ground rod to replace D-E-F.


    Really. If you have your feet on the ground and you touch the combiner box, you want the box to be at the same voltage as your feet. Best way to do that is to ground the box to a ground rod that is near your feet.

    --vtMaps

    Hi VT,

    My generator may have a floating neutral. Although the manual doesn't address this issue. Several sites seem to say that it may not have one. See this example link,
    "Yamaha EF6300iSDE 5,500 Floating Neutral"

    The only floating neutral that I know for sure exists is in the Flexpower Unit.

    I did not see any other floating neutrals in the 2 house panels. Then again, I am looking for something obvious (like I see in the Flexpower panel - you can see the wire that connects the G and N buss bars). Maybe the G-N bond can exist in something more subtle, like a mains breaker. But I only came across one obvious G-N bond, in the Flexpower panel.

    I agree that if "G" exists (the ground between the generator and the flexpower panel) then F is not necessary (F is the ground that would come from the little post that is on the front panel of my generator. That's because (EDIT) the generator is already grounded to the Flexpower panel which is wired with an AC ground in "D".

    Still reading the other replies, but I thought I'd post this for now. Very thankful for all your feedback.
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Wiring the bank

    Surfpath;

    It may be worth your while to get one of those plug-in outlet testers with the three LED's and plug it in to the generator and see what it reports.
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank

    VT,

    Regarding combining grounds D, E & F.

    Ground run "D" is an AC ground wire from the bus bar on the Flexpower panel. It grounds the AC side of the flexpower panel. E is a DC ground that runs from the DC enclosure on the flexpower panel. According to Outback's grounding chart for the panel -posted before- both the battery ground and the PV ground wires join to the DC bus bar, with a common ground wire going to the grounding rod.

    However, BB recommended sending no grounds to the FP panel enclosure:

    Per BB "I would suggest to drive a ground rod next the solar panel array (if not near the main ground rod) and bring the grounding wire (typically 6 awg recommended here) from the panels directly down to the ground rod. And if you have the combiner box there, bring a second ground wire from the box directly the local ground rod."

    In my ground diagram, B is the combiner box run, and C is the panel/mounting rails run.

    And E only services the battery ground.

    Again, this is not what I'd want.

    I'd love to only have what is on the Outback flexpower grounding chart, ie.....

    one house ground (fine, all houses have to have this),
    one Flexpower AC ground (also grounds the generator AC input),
    and one DC ground (a combination of the panels/mounting rails from the combiner box, plus the battery ground).

    But I can appreciate what BB said about avoiding bringing energy into the house, via the solar panels.

    ps. I will repost my grounding chart with some/all of your recommendations.
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank

    This next one is definately a newbie question....

    I believe I have to ground my battery bank. I have an 8 battery, 370 amp hr, 48v bank wired in one series - as described in post #7.

    The only new news is that I have mounted a 100amp battery terminal DC fuse to the (+) terminal on one of the batteries (the one which also has the inverter (-) cable attached to it).

    Where do you put (attach?) your battery bank ground wire? Does it connect to each battery? What AWG is recommended?
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank

    Actually, I see a nice answer from BB in this post
    so, no need to reply.

    "In general, one 6awg or heavier wire from the battery bank negative bus connection to your earth ground rod for your home.

    Generally, your green wire ground (frame grounds, etc.) should all make their common connection to one point too, at this common ground rod.

    And, your metal water pipes, propane gas line ground, etc. should all make their one ground connection to this common ground rod.

    The idea is, no matter what ac or dc circuit accidently makes a short to a piece of metal or pipe, it will flow safely to the common earth ground rod and back to a battery, inverter, or generator and trip a fuse or breaker.

    The other reason for tying all the grounds together this way is if lightning strikes a piece of metal pipe, electrical wiring, etc., all metal will be at the same voltage and keep the people safe (for example, reduce the chance of lightning hitting your electrical wiring and jumping over to you gas stove or sink)."
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Wiring the bank
    Surfpath wrote: »
    This next one is definately a newbie question....

    I believe I have to ground my battery bank. I have an 8 battery, 370 amp hr, 48v bank wired in one series - as described in post #7.

    The only new news is that I have mounted a 100amp battery terminal DC fuse to the (+) terminal on one of the batteries (the one which also has the inverter (-) cable attached to it).

    Where do you put (attach?) your battery bank ground wire? Does it connect to each battery? What AWG is recommended?

    If you try to ground the negative of each battery you will create a short or at least a current path across the batteries as the positive of one connects to the negative of the next. All you need do is ground the system negative. The wire only needs to be large enough to cause the breaker/fuse to go if a short occurs. In other words 6 AWG will usually do the trick the same as with the AC.
  • BB.BB. Super Moderators, Administrators Posts: 29,724 admin
    Re: Wiring the bank
    Surfpath wrote: »
    This next one is definately a newbie question....

    I believe I have to ground my battery bank. I have an 8 battery, 370 amp hr, 48v bank wired in one series - as described in post #7.

    The only new news is that I have mounted a 100amp battery terminal DC fuse to the (+) terminal on one of the batteries (the one which also has the inverter (-) cable attached to it).

    Where do you put (attach?) your battery bank ground wire? Does it connect to each battery? What AWG is recommended?

    OK--excluding lightning grounds for the moment--Think about what happens if something gets shorted...

    A typical AC circuit may have a 15-30 amp circuit breaker on it (120 to 240 VAC).

    A typical DC circuit may have a 100 amp to 400 amp circuit breaker on it (1,200 watts or more at 12-40 volt battery bank). Or ~3-10x the current as a similar "power" AC circuit. So if there are any DC to earth (or DC to DC shorts), the grounding system needs to carry 3-10x the amount of current in a short to pop a fuse/breaker as the AC would.

    So--Back at the flex power panel, Inverter, Charge Controllers, etc. are usually close together--And the conduit/green wire grounds/etc. should be around the same gauge wire as the wires suppling the power... For example if you have a 200 amp breaker with 4/O AWG power leads to an inverter, then you should have a 4/O grond cable to the DC Common Ground point too.

    So--the DC common ground bus (battery negative ground, DC safety ground common point) needs to manage the high surge currents from the fuses/breakers (remember, a good sized Lead Acid Battery bank can supply 1,000' to 10,000's of amp or more into a dead short). This is where I suggest not mixing AC and DC grounds together... Anything that can get shorted to a heavy DC circuit should carry a DC green wire too rated for that current (i.e., the DC distribution boxes, AC inverter chassis, etc.).

    If you check the NEC, you may find that you can use a (for example) 6 AWG ground wire with a 200 Amp main panel as safety ground--The idea is that the breaker will trip before the 6 AWG wire overheats.

    Now--Connecting the DC Battery Common ground bus to the main ground rod--That can be done with a 6 AWG wire (or even smaller possibly--check NEC). Ground Rods will never pass huge amounts of current at 12 vdc to 240 VAC--they are there to keep everything at zero volts--so you won't get a shock if you touch a water pipe or a grounded fuse box (I have received a shock from a ground rod driven 100' from the electric panel at a marine park--There was >60 VAC between the two "grounds"--That is why I suggest grounding exposed metal with a common ground wire).

    So, it is perfectly safe to run a 6 AWG ground wire from DC battery ground to the main ground rod in the home--You are not bringing 400 amps of DC power into the Home (I don't think you are).

    Of course, you can get more current through the ground rod when you get hit with a multi-million volt lightning strike--A different issue.

    And that was the discussion with the Combiner Box for the solar array... If there is a lightning strike, the ground wire from the combiner box directly to the local "lightning" ground rod. And, to make the system electrically safe if there is a DC or AC short circuit, a ground wire from the lightning ground rod to the main ground rod to pop the breaker/keep the box at "ground" level (if you touch the shorted box, you don't get a shock).

    Hope that all makes sense... Word Salad.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank

    OK, so take a 6 AWG green ground wire and attach it to one of the negative battery bolts on my bank (or the terminal negative bolt?). The other end of this earth wire goes to the earth rod (or to the ground bus bar in my e-panel, if that ends up going to the earth rod).

    Will that do it?
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank
    BB. wrote: »
    OK--excluding lightning grounds for the moment--Think about what happens if something gets shorted...

    ....
    Hope that all makes sense... Word Salad.

    -Bill
    Just seeing your last post now BB, reading it..
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank
    BB. wrote: »
    If you check the NEC, you may find that you can use a (for example) 6 AWG ground wire with a 200 Amp main panel as safety ground--The idea is that the breaker will trip before the 6 AWG wire overheats.

    Now--Connecting the DC Battery Common ground bus to the main ground rod--That can be done with a 6 AWG wire (or even smaller possibly--check NEC). Ground Rods will never pass huge amounts of current at 12 vdc to 240 VAC--they are there to keep everything at zero volts--so you won't get a shock if you touch a water pipe or a grounded fuse box (I have received a shock from a ground rod driven 100' from the electric panel at a marine park--There was >60 VAC between the two "grounds"--That is why I suggest grounding exposed metal with a common ground wire).

    So, it is perfectly safe to run a 6 AWG ground wire from DC battery ground to the main ground rod in the home--You are not bringing 400 amps of DC power into the Home (I don't think you are)

    OK, I think I get it a little more. Basically I need to consider the DC breaker that exists in the FP panel as part of the battery grounding equation.

    Aside: If you remember from a previous discussion, my Flexpower panel DC breaker is 175 amps (pretty high). Thus the need for 2/0 inverter battery cables. However I also added a 100 amp terminal fuse. This is to blow first and thus protect my inverter/other panel equipment.

    So I need to run a battery ground wire from the terminal negative post on my battery bank to the DC common ground bus bar in my panel. This wire has to potentially handle 175-200 amps (or 100-125 amps, if I always keep my terminal fuse installed?).

    From the common DC bus bar I can run a smaller wire to the actual ground rod. This is because the large DC surge threat is taken care of by the presence of my panel DC breaker? 9or terminal fuse) Am I getting there?
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • BB.BB. Super Moderators, Administrators Posts: 29,724 admin
    Re: Wiring the bank
    Surfpath wrote: »
    OK, I think I get it a little more. Basically I need to consider the DC breaker that exists in the FP panel as part of the battery grounding equation.
    Aside: If you remember from a previous discussion, my Flexpower panel DC breaker is 175 amps (pretty high). Thus the need for 2/0 inverter battery cables. However I also added a 100 amp terminal fuse. This is to blow first and thus protect my inverter/other panel equipment.

    Yes, the maximum power from the battery is now ~100 amp continuous (there is still a few seconds of higher surge in a dead short). Also, if you want to be "exact", you have XX amps from the solar charge controller and YY amps from the AC battery charger, etc. So--You do have a bit more current possible.

    But, in the end, the fusing current for a 6 AWG cable is around 670 amps--So, if you are well under that number--then the fuse/breakers should pop first.
    So I need to run a battery ground wire from the terminal negative post on my battery bank to the DC common ground bus bar in my panel. This wire has to potentially handle 175-200 amps (or 100-125 amps, if I always keep my terminal fuse installed?).

    Yep--In reality, you probably will not see more than the Isc-Array as the maximum shorted current possible (your only DC wiring leaving the "DC GROUND ZONE" is the solar array wiring and the grounding of the combiner box/mounting framework.
    From the common DC bus bar I can run a smaller wire to the actual ground rod. This is because the large DC surge threat is taken care of by the presence of my panel DC breaker? 9or terminal fuse) Am I getting there?

    In one way yes--And another, in my above sentence--You don't have any high current DC wiring outside of the "DC Grounding Zone".

    The most likely "faults" will be AC wiring (inverter output, other AC powered devices in the out building, etc.) shorting to the metal conduit/grounded DC cases--So that current will have to "return" back to the AC main panel via the 6 awg DC groundign wire back to the main ground rod (and then back up to the AC Mains Neutral/Earth bond point).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank

    OK, thanks for that in depth answer, and for the fusing wire current link.

    So, it's the other way around then. I can use a smaller wire, say 10awg, for the battery bank ground wire that runs from the terminal negative battery post to the DC ground bus bar (10 awg=fusing at 333 amps).

    Then at the DC common bus bar in the Flexpower, even though I have no other high current DC wires (just the Panel's Isc at around 23 amps), I need to account for AC faults from the AC side of the panel and therefore use a heavier gauge wire, say 6AWG, to go back to the ground rod? Phew, my head is spinning...
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • BB.BB. Super Moderators, Administrators Posts: 29,724 admin
    Re: Wiring the bank

    Yep--But you need to refer to the NEC for grounding wire sizing... You might be able to go as small as 8 or 10 awg wiring for grounding (and 15 amp circuits use 14 AWG wiring for their safety grounds).

    And there may be other requirements like 6 AWG minimum for buried ground wires (corrosion and strength against a shovel hit).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank
    BB. wrote: »
    Yep--But you need to refer to the NEC for grounding wire sizing... You might be able to go as small as 8 or 10 awg wiring for grounding (and 15 amp circuits use 14 AWG wiring for their safety grounds).

    And there may be other requirements like 6 AWG minimum for buried ground wires (corrosion and strength against a shovel hit).

    -Bill

    Bill how bout this for a last thought tonight. SO, to ground the batteries I connect 8 or 10 awg at the battery bank negative post (the terminal post where the negative inverter cable is also connected to the battery, right?). I run this to the common DC grounding bus bar in the flexpower.

    Now, I know you do not like mixing AC & DC grounds together, on account for DC's potential for high surge current. However, since the Panel's DC bus bar is 'protected' by a fuse and breaker, does this second 'DC ground wire run' (bus bar to rod) have to go to earth all by itself? Ie. can it be connected to another ground wire that is going to ground already?

    I know this will probably be problematic (creating a ground loop?). However, the reason for my thought is that I have tried to simplify my ground map, per Coot, but I have only been able to remove one ground (the 'backup' generator one). Five (just to the ground rod) still remain!
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • BB.BB. Super Moderators, Administrators Posts: 29,724 admin
    Re: Wiring the bank
    Surfpath wrote: »
    Bill how bout this for a last thought tonight. SO, to ground the batteries I connect 8 or 10 awg at the battery bank negative post (the terminal post where the negative inverter cable is also connected to the battery, right?). I run this to the common DC grounding bus bar in the flexpower.

    As far as I know--I would "earth ground" at the ground bus in the FlexPower... I don't see any reason to run a 8-10 AG from the battery negative post up to the FexPower when you have a 2/0 (or whatever) battery negative battery cable a few inches away.
    Now, I know you do not like mixing AC & DC grounds together, on account for DC's potential for high surge current. However, since the Panel's DC bus bar is 'protected' by a fuse and breaker, does this second 'DC ground wire run' (bus bar to rod) have to go to earth all by itself? Ie. can it be connected to another ground wire that is going to ground already?

    As long as the 8-10 AWG Green wire goes from the FlexPower negative bus to the main AC Ground Rod, there is no "mixing" of AC and DC grounds.

    If, for example, you had the 10 AWG green wire from the FlexBus to the Solar Charge Controller Chassis Ground and then headed off to the main ground rod--That would be mixing of grounding and using too small of AWG wire for the Charge Controller safety ground (or at least close to too small of AWG).
    I know this will probably be problematic (creating a ground loop?). However, the reason for my thought is that I have tried to simplify my ground map, per Coot, but I have only been able to remove one ground (the 'backup' generator one). Five still remain!

    I agree with simple... Makes the chances of ground loops less, and no confusion about where fault currents flow (120/240 VAC fault currents energize near by metal and go to AC green wire path to main panel, then to ground rod). DC faults energize DC Grounded metal to common battery negative bus bar...

    The Main Ground Rod to DC Ground Bus connection is not really a "high current" connection and 6-8-10 AWG is usually more than enough to trip an AC main panel breaker.

    If, for example, there was no 120.240 VAC connection from the outbuilding to the main house--Then you would not even need to connect to the house main ground rod. As there is no way for House's 120 VAC to fault/energize anything in the outbuilding.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank
    BB. wrote: »
    As far as I know--I would "earth ground" at the ground bus in the FlexPower... I don't see any reason to run a 8-10 AG from the battery negative post up to the FexPower when you have a 2/0 (or whatever) battery negative battery cable a few inches away.

    As long as the 8-10 AWG Green wire goes from the FlexPower negative bus to the main AC Ground Rod, there is no "mixing" of AC and DC grounds.

    If, for example, you had the 10 AWG green wire from the FlexBus to the Solar Charge Controller Chassis Ground and then headed off to the main ground rod--That would be mixing of grounding and using too small of AWG wire for the Charge Controller safety ground (or at least close to too small of AWG).

    I agree with simple... Makes the chances of ground loops less, and no confusion about where fault currents flow ...
    The Main Ground Rod to DC Ground Bus connection is not really a "high current" connection and 6-8-10 AWG is usually more than enough to trip an AC main panel breaker.

    If, for example, there was no 120.240 VAC connection from the outbuilding to the main house--Then you would not even need to connect to the house main ground rod. As there is no way for House's 120 VAC to fault/energize anything in the outbuilding.

    -Bill

    Bill,
    Thank you for working with me on this one. Grounding is one of the most challenging aspects of Solar/Off Grid, no doubt. By the way, to clarify, I don't have a 'outbuilding,' my solar room is located on the 1st floor of my house.

    When you say "I would 'earth ground' at the ground bus in the flexpower," I am not sure what you mean. Do you mean that my 2/0 inverter cables are a sort of ground wire as well, and I don't need a dedicated ground wire coming from my batteries? Ie that I just need a ground wire installed from my flexpower panel DC ground bus bar to the ground rod? No need to do anything else? That would be a little simplification.

    Again, from re-reading all of the posts I still count 5 unique grounding runs to my one grounding rod, and that still seems to be complex.

    Here they are:
    1) Panels/rails direct to rod
    2) Combiner box direct to rod
    3) Flexpower AC to rod (incorporates both the flexpower AC earth plus the generator earth)
    4) The regular house earth (plugs, lights etc) to rod. This ground wire runs from the main house breaker panel direct to the rod
    5) The DC ground bus bar to rod.

    Coot suggested that

    a) The panel frame/mount ground should go directly to the rod, without entering the house (just like you did).

    b) The ground of the combiner box would connect to the AC and DC grounds of the Flexpower, where the Neutral-Ground bond is and then to the ground rod (aside, that would be a little simplification since the PV ground would "share" the Flexpower DC run in this case. By the way Coot, in the outback ground map the ground from the combiner box goes to the DC ground bus. Also, the Neutral-ground bond in the Flexpower is located in the AC enclosure - dont know if that helps).

    c) The generator's wiring with its N-G bond would connect to the AC side of the Flexpower via the transfer switch. You have no GFCI on the generator output so there should be no problem there (ground loop is contained). If there is, leave out the ground wire from the gen to the Flexpower and let it "float". (aside: help, dont have a tester, will just have to run the genny when I charge the batts tomorrow and see if the GFCI in the flexpower panel pops. I will keep the genny's earth on - dont want to leave it unearthed).
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank

    Signing off for tonight (a little confused but very grateful for the help):

    I have not installed all the earths and the panels yet. However, I feel I have to charge the batteries soon (tomorrow).

    This is what I have done today in order to set up the generator to charge my bank:

    1) attached the generator to the "AC in" side of the flexpower panel (live, neutral and earth wires)
    2) attached the AC ground in the flexpower panel and run it to the ground rod (this is ground "D on my grounding plan)
    3) installed the battery temperature sensor
    4) wired the battery bank (will attach inverter cables to the batteries just before charging - negative cable 1st I believe). When I flip the breaker this will power up the panel.

    From today's chat (thanks BB) I realize that I need to have my DC Bus bar grounded with #8 or #10 AWG. This would ground my batteries (assuming that the inverter cables are also part of this equation).

    When this last step is done I should have:
    a) grounded the Genny through the AC side of the Flexpower
    b) grounded the AC side of the flexpower panel
    c) grounded the DC side of the plexpower panel (ie the batteries).

    Hopefully this will work. Hopefully the only G-N bond is in the Flexpower panel, that my genny has a floating neutral, and that the house also does not have a floating neutral.

    -Gnite. :-)
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • BB.BB. Super Moderators, Administrators Posts: 29,724 admin
    Re: Wiring the bank
    Surfpath wrote: »
    Bill,
    Thank you for working with me on this one. Grounding is one of the most challenging aspects of Solar/Off Grid, no doubt. By the way, to clarify, I don't have a 'outbuilding,' my solar room is located on the 1st floor of my house.

    Oh... OK. Was not sure--thought it may have been a detached garage.
    When you say "I would 'earth ground' at the ground bus in the flexpower," I am not sure what you mean. Do you mean that my 2/0 inverter cables are a sort of ground wire as well, and I don't need a dedicated ground wire coming from my batteries? Ie that I just need a ground wire installed from my flexpower panel DC ground bus bar to the ground rod? No need to do anything else? That would be a little simplification.

    Yep--You have your 2/O battery negative lead going the the FlexPower ground bus (I think). So, attaching the 6-10 AWG green wire from the FlexPower Ground Bus to the main ground rod is just fine.

    There is (usually) nothing magic where you attach the Green Wire for your single point of ground. Ideally--The Ground connection is supposed to be such that it does not become disconnected accidentally (for example, say you ground at the battery--Now, if you unbolt the 2/O battery cables for some reason, you have lifted the safety ground from your power panel too.

    By the way--Just to make it clear, I am assuming that the FlexPower DC Ground Bus is also connected to the sheet metal box (electrically). Just want to make sure--The Ground bus could be electrically isolated too and there is another "green" screw intended for "metal box/chassis safety ground".

    Again, from re-reading all of the posts I still count 5 unique grounding runs to my one grounding rod, and that still seems to be complex.
    Here they are:
    1) Panels/rails direct to rod YES
    2) Combiner box direct to rod YES (could also be connected via #1 if it is a pretty direct run)
    3) Flexpower AC to rod (incorporates both the flexpower AC earth plus the generator earth) NOT SURE (#5 vs #4)
    4) The regular house earth (plugs, lights etc) to rod. This ground wire runs from the main house breaker panel direct to the rod YES (Neutral Bus Bar/Ground Bar common)
    5) The DC ground bus bar to rod.
    Probably YES. Lets talk....[/QUOTE]

    Sorry--I don't know the FlexPower product--So I may be saying some dumb stuff/asking the questions that have already been answered.

    #3 --- FlexPower AC to Rod... Not sure what that is. Is that the bonding of the AC Neutral from the Inverter? Or just some sheet metal ground connection to the inverter's AC earth ground? Normally, the AC Inverter's "White/Neutral" wire is tide back to the home's Main Panel Neutral Bus Bar (grounded to earth). The Black wire would be switched with an AC transfer switch, typically inside the AC inverter.

    #5 is as I guessed before... A block of copper or brass that is bolted electrically to the metal box with a bunch of connection points for the Battery negative cable and other DC negative wiring.
    Coot suggested that

    a) The panel frame/mount ground should go directly to the rod, without entering the house (just like you did). YES
    b) The ground of the combiner box would connect to the AC and DC grounds of the Flexpower,

    To be really clear--There are probably two "Grounds" in the combiner box. There is usually an insulated ground bus bar that is connected to the solar negative wiring. And the positive wiring from the breakers goes to second DC positive bus bar--also insulated. And there is a second ground connection (typically a Green Screw with a ground symbol stamped in the sheet metal or a ground label).

    There is no (direct) DC ground connection to the negative bus bar in the combiner box--The "black and red" bus bars connect to the solar charge controller panel input terminals.

    The direct to local ground rod connection is from the green screw/box sheet metal ground.
    where the Neutral-Ground bond is and then to the ground rod (aside, that would be a little simplification since the PV ground would "share" the Flexpower DC run in this case.

    I am a bit confused here... "Neutral" is, in theory the AC white wire (center tap of a 120/240 VAC transformer).

    The PV Ground--Which one are you talking about?

    There is the PV Frame ground (direct to local ground rod for lighting ground).

    The other one is the Black (negative) and Red (positive) wiring from the solar array to the Solar Charge Controller. Typically, the Red and Black PV wires simply attach to the PV Input of the charge controller... No other connections are made (no earth/DC grounds--There are some variations here--But we can ignore them for now).
    By the way Coot, in the outback ground map the ground from the combiner box goes to the DC ground bus.

    Yes, I have seen drawings which show the Combiner Box Green Wire (to box sheet metal ground) going to the sheet metal ground screw/bus in the DC power panel.

    If the combiner box is near the solar array--I would bring the sheet metal box ground directly to the ground rod.

    If the combiner box is mounted inside the building, then you could bring the box sheet metal ground to the flexpower green wire/chassis ground.
    Also, the Neutral-ground bond in the Flexpower is located in the AC enclosure - dont know if that helps).

    If this was a stand-alone off grid installation, then you could have the AC Neutral/Ground Bond in the FlexPower box or local AC encloser (main panel).

    If this is a backup power system with AC from the house utility panel to the AC inverter (or to the AC Transfer Switch) then to a sub panel (where you 'protected' loads are connected), then you would not want the second Neutral to Earth bond.

    c) The generator's wiring with its N-G bond would connect to the AC side of the Flexpower via the transfer switch. You have no GFCI on the generator output so there should be no problem there (ground loop is contained). If there is, leave out the ground wire from the gen to the Flexpower and let it "float". (aside: help, dont have a tester, will just have to run the genny when I charge the batts tomorrow and see if the GFCI in the flexpower panel pops. I will keep the genny's earth on - dont want to leave it unearthed).

    I think the code is Generators under ~3.5 kW have floating neutrals. And Geneators over ~3.5 kW are supposed to have neutral tied to generator's frame ground, which then is supposed to be tied to a ground rod/cold water pipe, etc....

    The confusion is that the code for each device assumes it is the sole source of power (AC Main Utility Panel; Large Off Grid Inverter; Large Genset, etc.)... When you connect all of these together in one place--it causes lots of issues.

    You can lift the Neutral bonds in a couple of the devices, or use a multipole AC transfer switch (and some inverters have one or more internal transfer switches).

    A multi pole AC Transfer Switch can also switch the Neutrals (use generator ground neutral when generator is running, use AC Inverter neutral when it is running, use the AC main utility neutral, etc.)...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank

    "Yep--You have your 2/O battery negative lead going the the FlexPower ground bus (I think)"

    The 2/0 negative lead is actually bolted to a shunt on the inverter. Here is a snapshot of the Flexpower wiring (OFF-grid).
    The PV negative connection is right in the middle of the diagram.
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • BB.BB. Super Moderators, Administrators Posts: 29,724 admin
    Re: Wiring the bank

    From the drawing:

    The green wire in the combiner box just goes into the box, connects to sheet metal grounding screw and goes back out--It does not connect to the negative bus inside.

    There are two grounding buses in the FlePower panel... The one below the inverter should be the main DC grounding bus--and should be electrically connected to the FlexPower box sheet metal (DC Safety Ground in my terms).

    The upper AC grounding bus bar should be insulated from the rest of the metal box. If it is grounded then it is identical to the DC Safety Ground bus and it is "impossible" to install the system without creating a ground loop as drawn.

    Of course, if you use metal conduit for your AC (or some DC) wiring--Then you have the metal conduit/EMT carrying your ground too. And another source of ground loop (Conduit goes back to AC main panel carrying the sheet metal ground of the FlexPower system--which is technically at DC Safety Ground. And would be in parallel with the DC Safety Ground to main ground rod connection).

    In some ways, it is "overkill" to get this deep into the grounding discussions. From a people point of view, having all exposed metal (that anybody can touch) tied together with copper wire/metal conduit and somehow tied back to the earth ground rod (and cold water pipe) is as safe as you can get... It is almost impossible to touch two pieces of metal and get a shock--A good/safe installation. And a short circuit cannot "energize" any exposed metal as it will trip a circuit breaker/fuse in the circuit.

    The issue of ground loops... What you want to avoid is tying the DC Negative cable and an Earth Ground electrical path (green wire or metal conduit, etc.) together in two places. This can cause load current to flow in two parallel paths. Normally these type of connections only occur if there is a short circuit (say an inverter - DC cable gets a cut on a sharp sheet metal hole). It is also a "possible problem" with AC power circuits too--Just the nature of the beast and there is no easy way to prevent/detect this problem other than doing a safe installation with smooth metal surfaces and bushing to protect wiring going through holes/conduit ends.

    Where this can become a "real issue" is when using 12 volt appliances designed for automotive use... For example, a 12 volt car radio has the + wire input and uses the metal case for ground return. As well as the ground for the antenna wiring.

    Here is a point at which 12 volt return is "tied" to 12 volt ground. And there is no "good way" to wire up a car radio to match the ideal of power wiring. Instead, you have the choice of wiring +/- wiring to the radio and "float" the ground. Or tie +/ground to the radio and have power returning via the "green wire".

    And if you tied + and -/green wire together--You have a ground loop where you could get current from the return wire (negative) finding a second path through the green wire back to ground rod and then back up to the battery common negative bus ground. This is what you want to avoid.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Wiring the bank

    Surfpath, does your flexpower have a DC GFDI (ground fault Detector Interrupter)? It is two (or more) circuit breakers ganged together. One of the breakers will be rated for an amp or half amp and have a resister across its terminals.

    If you do have this setup, that GFDI is your DC bonding to ground. You do not want or need another DC bond.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank
    vtmaps wrote: »
    Surfpath, does your flexpower have a DC GFDI (ground fault Detector Interrupter)? It is two (or more) circuit breakers ganged together. One of the breakers will be rated for an amp or half amp and have a resister across its terminals.

    If you do have this setup, that GFDI is your DC bonding to ground. You do not want or need another DC bond.

    --vtMaps

    Yes the flex does have a DC GFDI. The Inverter + cable connects to it on the above wiring chart.

    Here are some other certainties.
    • Per the electrician who helped build my house there is no ground to neutral bond anywhere in the house wiring.
    • My generator is the Yamaha6300ISE and does not have any GFDI outlets (the US 6300ISDE version does). Aside: perhaps this means it has a floating neutral?

    So the only G-N bond should therefore be in the flexpower panel. Hopefully.

    I feel I must run the genny today and charge those batteries. I am a little nervous. Lots and lots of effort and money to get that gear.

    For this initial charge a ground wire from the genny goes into the flexpower AC enclosure (attached to the common AC ground bus bar just like in the diagram on post 50). The panel then has a ground wire that goes to the earth rod (again, just as in the diagram). I believe I also need a battery ground. After reading BB's post, I am not quite sure how to do this. Do I just wire the DC ground bus bar on the lower enclosure of my panel direct to ground with a 10 AWG wire (thus relying on the Flexpower inverter cables to make the rest of the ground connection?). Or do I need another wire from the batteries themselves?

    I have the PV + and neutral wires connected to the flexpower panel, but they just go in conduit to the roof above (dry eave, coiled up waiting for the panels to be mounted. Obviously, the AC out switch on the panel will remain OFF during this initial charge.

    I hope this initial "charging" set up will work. -SP
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Wiring the bank
    Surfpath wrote: »
    Yes the flex does have a DC GFDI.
    <snip>
    I believe I also need a battery ground. After reading BB's post, I am not quite sure how to do this. Do I just wire the DC ground bus bar on the lower enclosure of my panel direct to ground with a 10 AWG wire (thus relying on the Flexpower inverter cables to make the rest of the ground connection?). Or do I need another wire from the batteries themselves?

    Then you do not need to ground the battery negative. Your PV negative and your battery negative are in continuity (at the charge controller). If either is bonded to ground, then both are. And they both are bonded to ground by the DC GFDI. This is how Outback recommends to do it. It meets the NEC. It has been discussed quite a bit on this forum as well as the Outback and Midnite forums, and its a bad and dangerous aspect of the code. One of the several bad things about it is that when it trips, it breaks the bond to ground which means that your entire DC system may be floating at Voc above ground. You could get a lethal shock from touching a DC light fixture or even your negative battery cable.

    The sad thing is that when you finally figure out and understand what to do about grounding, you find that the industry's way of meeting code is dangerous and ought not to be allowed. In some ways ignorance is bliss:cry:

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Wiring the bank
    Surfpath wrote: »
    I feel I must run the genny today and charge those batteries. I am a little nervous.
    <snip>
    I hope this initial "charging" set up will work. -SP

    Surfpath, we're all waiting to hear how it went...
    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank
    vtmaps wrote: »
    Surfpath, we're all waiting to hear how it went...
    --vtMaps
    OK, fairly challenging stuff. Imagine not having any reliable on-site electrical help, ordering equipment you can't return (regardless of warranty), spending as much in duties and shipment as the cost of the system itself. Receiving batteries after a month long transit that need a charge soon, not knowing where the G-N bonds really are, and trying to read and make sense of 9 Outback manuals.

    Well, we flipped the battery breaker and, with a "new electronics wiff" in the air, the system sprung to life....50 little Trojan volts. Then we inputted the parameters into the mate, started the generator and flipped the AC breaker switch. After 30 seconds it scooped up those generator electrons went straight to absorb...phew.

    After an hour of absorb (like many advised) we started a 3 hour EQ. My logbook is at home, but SG's went from about 1.225 (before charge) to 1.250 (around start of eq) to 1.260 to 1.270/1.275 at the end of the EQ, We stopped when they seemed to slow down and not want to raise much more.

    It took about 58 Amp hours (about exactly what you said BB), but ~ 5 hours charge instead of 2.2. What was surprising was how little power the EQ took from the Genny (it can put out ~23amps at 230v). I guess because the FX tapers it. I should have tracked the numbers, but it went something like 14 amps for the first 15 minutes then 11 amps for half an hour, 9 amps (15 mins), 7 amps (15 mins), 5 amps (45 mins), and then 2-3 amps for an hour. I remember reading about how some outback inverters have difficulty charging in honda-yamaha "eco" more, but I switched to eco for the last hour and everything seemed fine. I am pretty sure eco could have handled the whole event. At peak charge, 3 bars on the (6 bar?) power charge led were on.

    So, we have lights without generator noise after 5 months of 2.6 amp hour power tool battery light. Amen. It was weird going into a room and turning on a light. We will turn on the fridge/use the washer after the PV panels are installed over the next week. I think I have assembled a neat mounting system.

    Thank you my NAWS friends. Coot, BB, Vt, Vic, Inet, Wayne esp. I feel very blessed to have your support and guidance.
    -SP
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Wiring the bank
    Surfpath wrote: »
    I remember reading about how some outback inverters have difficulty charging in honda-yamaha "eco" more, but I switched to eco for the last hour and everything seemed fine. I am pretty sure eco could have handled the whole event.

    I never read about Outback chargers not working with eco mode. My experience with Outback is that it is a relatively soft start and my eu2000 handles it easily in eco mode.

    btw, A couple of posts back I explained that your flexpower comes with a bond between ground and your Battery negative, and that it is a controversial method of bonding. Here is a good read: http://midnitesolar.com/smf_forum/index.php?topic=142.0

    Although the thread is at Midnite it is relevant to you, they do their DC-ground bonding the same dangerous (but to code) way as Outback, Magnum, and most others.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • SurfpathSurfpath Solar Expert Posts: 393 ✭✭✭
    Re: Wiring the bank

    A quick update: I am still charging the bank with the genny. Eco mode has been working out well. However....

    The tail end of the charge process is a pain in the tail.

    I am only using LED lights (and an inverter in NON-Search mode:p). Typically I only draw down the batts to 75% SOC (1.225). It takes me about 4 days to get this point.

    My 5.5 hour charge process usually involves a 5 hour absorb, but this only brings up SOC to 1.260. I don't get to the 1.277 that Trojan recommends, mainly because I don't have the time to monitor the genny for longer than 5-6 hours (busy time now, not at home much). I wish I had my panels up now to do the tail end of this process. Hope to get them up in a few weeks time.

    When I first got the batts a month or so ago, I performed an EQ, which brought them to 1.270/1.275.

    For the past 5 charge cycles I seem to be going from 1.225 (75%) to 1.260 (low 90's). The last 2-3 hours of my current 5 hour charge process is at 100-300 watts of generator power.


    Is not getting them up to 100% consistently hurting my new batts?

    Should I make the effort to run that 5.5kw Yammy (on eco mainly) for 8 hours?
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • BB.BB. Super Moderators, Administrators Posts: 29,724 admin
    Re: Wiring the bank

    As long as you get the batteries >90% several times a week and have them spend a little time as possible below ~75% state of charge (i.e., recharge >80% next day)--You should be fine.

    There is no need to get to 100% multiple times a week--especially if it means running your genset for hours on end at very low charging currents. Equalization (charged battery, lots of bubbling, batteries getting hot) is hard on batteries.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Wiring the bank

    I think you already know the answer. If they were mine I'd be doing a short EQ on them to get the SG up. If you do it every 10-20 cycles, once a month, every six months the longer you wait the bigger chance you'll start getting crystallized Sulfate that causes to lose capacity over time.

    In your case you can raise the charging Voltage and see if you can get it up. The 2 things you can change is Time and Voltage, doing a EQ just breaks the Charging Profile of your regular routine by raising the voltage. The Time you can't do much about because the batteries are limiting the current they will accept. Watch the temperatures and make sure they are below 115 F.

    Everything you do or don't do is a Tradeoff with a Battery.
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Wiring the bank
    Surfpath wrote: »
    Is not getting them up to 100% consistently hurting my new batts?

    That's a very good question. I wish I knew the answer. Bill (BB.) says "Equalization (charged battery, lots of bubbling, batteries getting hot) is hard on batteries". That may also apply to daily full charging. Stephendv has written about how SMA controllers and chargers do NOT do a full charge every day.

    On the other hand, most battery manufacturers suggest that every discharge-charge cycle should be to full charge.

    One thing seems clear to me... gassing is what cures electrolyte stratification. If there is any stratification, the SG you measure is lower than the actual SG at the lower plates. The higher SG on the lower portions of the plates promotes sulfation on those plates.

    Bottom line: gassing is hard on the battery and not gassing (= stratification) is hard on batteries.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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