A few Newbie Questions about Grounding on Solar Panels and battery

charlie hepler
charlie hepler Registered Users Posts: 6 ✭
in Off Grid Solar & Battery Systems #1
Hey Guys/Gals,

I am a newbie and been lurking for a while but finnaly got my feet wet and jumped in! I have a few newbie questions and hope you folks overlook my lack of knowledge. I have done some searches but have not found a specific answer to my questions. With that said, here goes.

My Setup: These Panels are all on my Tool shed roof and run about 20 feet to my Solar Wall mounting area.

(2) Renogy 100 Watt panels
(Volts): 22.5V
(Short-Circuit Current): 5.75 Amp

Panels are paralleled at the panels and going to a Square D 30 amp breaker box on a 15 amp QO Breaker.
Morningstar Prostar 30amp CC.

(1) Grape Solar 250Watt panel
(Volts): 30.7v
(Short-Circuit current):8.72 Amp
15 Amp QO Breaker
Morningstar MPPT Sunsaver 15amp CC.

These are going to a 245AH AGM 12 Volt Battery and then hooked to a Xantrex Powerwatt Sw600 600w True Sinewave Inverter.


I have the Panel Frames, Roof Tilt Mounting System, Square D Breaker Box surface and DC/AC Inverter GREEN WIRE Connected to a Ground wire/Bar buried 8 feet into the ground.

Note: The Negative bus bar in the Square D Box is tied together in the box but isolated from the box itself. The Positive wires are seperate going to their own breakers.

My questions is:

1. Should I have the panels negative wires grounded in or to the box?
2. Should I have the Battery Grounded.
3. If they should all be grounded then do I use the same ground stake/wire?
4. Should I use a Remote TS on the Morningstar Mppt controller as the battery and CCs are only about 5 feet apart on the same wall inside my building.

Thanks in advance for any help you folks can offer!

Charlie
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: A few Newbie Questions about Grounding on Solar Panels and battery

    Welcome to the forum Charlie.

    Do you want to hear about the NEC regs requiring ground fault protection on the DC wiring now/ No, probably not; you just want it to work. :p

    My version of grounding which seems to work even if it doesn't meet code:
    Panel frames & mounts should be grounded via a separate wire running outside the building to reduce the risk of introducing stray Voltage from lightning to the inside of the building.
    Metal cases of components grounded.
    Negative battery terminal grounded.
    One side of AC on a pure sine inverter grounded.
    All these connected to the same ground rod.

    Should you use an RTS on one battery that's a few feet away from the controller? Probably, but not critical.

    Your Renogy panel specs don't make sense: 100 Watts with a Voc of 22.5 is normal, but the 5.75 Amps would be Imp not Isc. Anyway, the two together only put out <12 Amps max so the 30 Amp Prostar is overkill but leaves room for expansion.

    That 250 Watt Grape Solar can max out the 15 Amp Morningstar MPPT, but no harm done. All told you'd have just under 30 Amps peak current which would be the upper end of practicality for the 245 Amp hour battery.

    As a whole it ought to work well and give you a bit over 1 kW hour AC maximum.
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  • charlie hepler
    charlie hepler Registered Users Posts: 6 ✭
    #3
    Re: A few Newbie Questions about Grounding on Solar Panels and battery
    Cariboocoot wrote: »
    My version of grounding which seems to work even if it doesn't meet code:
    Panel frames & mounts should be grounded via a separate wire running outside the building to reduce the risk of introducing stray Voltage from lightning to the inside of the building.
    Metal cases of components grounded.
    Negative battery terminal grounded.
    One side of AC on a pure sine inverter grounded.
    All these connected to the same ground rod.

    Thanks Cariboocoot for getting back to me so quickly!

    I appreciate the welcome and the quick answers to my questions.
    I don't know the diff on the panels info for volts and amps as I just cut and pasted from the image I had from the back so I could have made a mistake. :)Should have been 5.29 Volts IMP.

    I understand most of this info but am a little confused on 1 thing.

    I have all the outside equipment going straight to the Grounding rod as you suggest.
    I have the Square D breaker panel case and the Green wire from the back of the Inverter going to ground through the floor and to the same grounding rod as the outside equiptment.

    So should I ground the CCs cases as well as grounding the battery NEG Post to the same ground wire with the Square D panel and inverter green wire?

    What about the NEG leads from the solar panels that connect to the NEG bus bar in the Square D breaker panel (currently isolated)?
    .... should they also be connected to the Square D panel case ground with the battery and cases of the CCs?

    "One side of AC on a pure sine inverter grounded"

    Is this done from inside the Inverter case?
    I am a little confused as there are 3 wires coming from the back of the inverter. Red, Black and Green?

    Sorry to sound so uninformed but I have read a lot and this grounding issue seems to be a source of confusion from all the stuff I have read.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: A few Newbie Questions about Grounding on Solar Panels and battery
    charlie hepler wrote: »
    So should I ground the CCs cases as well as grounding the battery NEG Post to the same ground wire with the Square D panel and inverter green wire?

    Yes. This is the electrical safety ground. In case something shorts to one of those cases the ground will cause the current to go high enough to trip the circuit protection. BTW, if you don't have fuses/breakers on the positive wiring what happens is a fire.
    What about the NEG leads from the solar panels that connect to the NEG bus bar in the Square D breaker panel (currently isolated)?
    .... should they also be connected to the Square D panel case ground with the battery and cases of the CCs?

    There is no need to separately ground negative wiring on panels, charge controller, et cetera; it is all "pass through" wiring and connects to the negative battery post.
    "One side of AC on a pure sine inverter grounded"

    Is this done from inside the Inverter case?
    I am a little confused as there are 3 wires coming from the back of the inverter. Red, Black and Green?

    The is for the AC output. Depending on just what the inverter is, there are three wires to the AC side which are Hot, Neutral, and Ground. The ground is nothing as far as the inverter is concerned until it is connected to the grounding rod. The Neutral is also hot until it is connected to the ground. Some inverters have this N-G bond built in (especially those with plug outlets instead of hard-wired output) and some can not have it (most MSW type inverters). You really have to check the specific manual for your inverter on this, as you only want one N-G bond (if any) in one location.

    Your red, black, and green wires are most likely the DC in (positive, negative, and ground respectively).
    Sorry to sound so uninformed but I have read a lot and this grounding issue seems to be a source of confusion from all the stuff I have read.

    That is probably the ultimate truth! It doesn't help when they change the regulations so that previous grounding rules get negated. To say nothing of those rules which don't make sense from an engineering point of view. Hard to follow rules that change and don't make sense. :p
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #5
    Re: A few Newbie Questions about Grounding on Solar Panels and battery

    The one question I have, Marc, is not about the grounding, but with the Grape PV with its 30.7 Vmp being so far off from the probable 18-ish Vmp of the two others. If the two 100 W PVs were seriesed for 35.5-36 V Vmp, this would be about 15% off from the two 100s in series.

    Perhaps I have not had enough coffeeeeeeeee this AM. What am I missing? 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.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: A few Newbie Questions about Grounding on Solar Panels and battery
    Vic wrote: »
    The one question I have, Marc, is not about the grounding, but with the Grape PV with its 30.7 Vmp being so far off from the probable 18-ish Vmp of the two others. If the two 100 W PVs were seriesed for 35.5-36 V Vmp, this would be about 15% off from the two 100s in series.

    Perhaps I have not had enough coffeeeeeeeee this AM. What am I missing? Thanks, Vic

    You're missing that he has that one connected through a Morningstar MPPT 15 controller.

    Better get that second cup! :p
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #7
    Re: A few Newbie Questions about Grounding on Solar Panels and battery

    OH, Yea, now I see the PWM ... OOOPPppppssss Thanks off for coffee. 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.
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  • charlie hepler
    charlie hepler Registered Users Posts: 6 ✭
    #8
    Re: A few Newbie Questions about Grounding on Solar Panels and battery
    Cariboocoot wrote: »
    Yes. This is the electrical safety ground. In case something shorts to one of those cases the ground will cause the current to go high enough to trip the circuit protection. BTW, if you don't have fuses/breakers on the positive wiring what happens is a fire.

    I do have all the Positive wires Fused from the CCs to the batteries (20Amp) and from the battery to the DC/AC Inverter I have a 140amp breaker on the positive wire.
    Cariboocoot wrote: »
    The is for the AC output. Depending on just what the inverter is, there are three wires to the AC side which are Hot, Neutral, and Ground. The ground is nothing as far as the inverter is concerned until it is connected to the grounding rod. The Neutral is also hot until it is connected to the ground. Some inverters have this N-G bond built in (especially those with plug outlets instead of hard-wired output) and some can not have it (most MSW type inverters). You really have to check the specific manual for your inverter on this, as you only want one N-G bond (if any) in one location.

    Your red, black, and green wires are most likely the DC in (positive, negative, and ground respectively).
    It appears that the cases on the Morningstar CCs are plastic? The Inverter shows you connecting the chassis ground green wire to ground only. It has 2 of the 110v GFCI plugs on the front of the unit.

    Cariboocoot wrote: »
    That is probably the ultimate truth! It doesn't help when they change the regulations so that previous grounding rules get negated. To say nothing of those rules which don't make sense from an engineering point of view. Hard to follow rules that change and don't make sense. :p

    I have my Arays connected to my tools shed to run it and have a little backup if the power goes out but have no intention of going on grid. I guess if I change my mind I would then have to get a professional to do the work as I can't make any sense out of all the NEC stuff that changes constantly as you mentioned.

    Thanks again for the replies and to let you know I got the system running yesterday with both arays and was seeing some great AMP/Watt #s coming from the panels!

    charlie
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