diy solar

diy solar

Grounding Check

theHouserHouse

New Member
Joined
Sep 5, 2020
Messages
27
I want to make sure we get the grounding correct on our travel trailer solar system. We have decided to go a different direction and build a kind of solar generator mounted inside the dinette bench and just plug our RV's shore power cored into it.
I've read the product manuals and here's what they have to say about grounding...

GROUNDING INFO FROM THE MANUALS

Victron SmartSolar MPPT 150/60-Tr Solar Charge Controller:
● Battery grounding: the charger can be installed in a positive or negative grounded system.
Note: apply a single ground connection (preferably close to the battery) to prevent malfunctioning of the system.
● Chassis grounding: A separate earth path for the chassis ground is permitted because it is isolated from the positive and negative terminal. (would this be inverter ground?)
● The USA National Electrical Code (NEC) requires the use of an external ground fault protection device (GFPD). These MPPT chargers do not have internal ground fault protection. The system electrical negative should be bonded through a GFPD to earth ground at one (and only one) location.
● The charger must not be connected with grounded PV arrays. (one ground connection only)
● The plus and minus of the PV array should not be grounded. Ground the frame of the PV panels to reduce the impact of lightning.

VertaMax Inverter:
The VertaMax is designed to work with grounded electrical systems. In the inverter, ground is not connected to the input terminals. .Use a copper wire to connect the grounding terminal on the VertaMax enclosure to earth ground or chassis ground. The grounding terminal is located on the DC Input end of the inverter.

Vehicle installations: Connect to the chassis of the vehicle.

Do not connect the system negative conductor to this terminal. NEC requires to use of an external ground fault protection device (GFPD). The system electrical negative should be bonded through a GFPD to earth ground at one (and only one) location. The grounding point may be located in the solar/wind circuit or the battery circuit.


After reading both of these instructions I think the following is how to ground this system.

· Ground the batteries. I believe this can be done at the battery monitor shunt, on the side of the shunt closest to the battery. The ground wire will connect to the chassis.

· Ground the frame of the PV panels. We have 8 panels: 2 pairs are mounted together. This sounds like I need to ground the 4 separate panels and the 2 pairs, 6 grounding points all together. Ground them to the chassis.

· Solar Charge Controller grounding not needed because the ground is at the battery shunt.

· Inverter grounding ?unsure? The manual says to ground at the chassis, but the charge controller says only one grounding point. So I’m thinking no additional ground for the inverter, just the one ground at the battery shunt.

In the attached diagrams, the green wire is the ground.
Thoughts?
 

Attachments

  • Wire N Equipment Diagram 1.jpg
    Wire N Equipment Diagram 1.jpg
    155.1 KB · Views: 63
  • Wire N Equipment Diagram 2.jpg
    Wire N Equipment Diagram 2.jpg
    96.2 KB · Views: 68
Talking about a small system on the average RV or Van.
1/ The shunt must have only the negative battery terminal connected to one side. The other side of the shunt has all of the other negative returns. Including the chassis.
2/ Connect the "grounding terminal on the VertaMax enclosure" to the vehicle chassis, your green wire.
3/ The inverter doesn't have to connect to mother earth ground. Your yellow wire.
4/ There is no proven requirement to wire a solar panel frame to the Van Vehicle. I guess there could be a very large system on a very large vehicle.
5/ If you are planning to plug into a grid with a shore line, the chassis must be connected to the mother earth ground with the green wire.
6/ Never bond the white neutral to anything but the shore cord white neutral wire.
7/ Always check that the pedestal for your shore line has a quality green, mother earth ground, connection to the entry panel from the grid.
 
Last edited:
These two items seem to conflict.

● The charger must not be connected with grounded PV arrays. (one ground connection only)

· Ground the frame of the PV panels. We have 8 panels: 2 pairs are mounted together. This sounds like I need to ground the 4 separate panels and the 2 pairs, 6 grounding points all together. Ground them to the chassis.
 
Neither PV positive nor negative to be grounded.
But grounding frames is good.
 
Neither PV positive nor negative to be grounded.
But grounding frames is good.

Victron is referring to taking the negative lead from the PV array and grounding that? They aren't referring to grounding the panel frame? That seems confusing.
 
Talking about a small system on the average RV or Van.
1/ The shunt must have only the negative battery terminal connected to one side. The other side of the shunt has all of the other negative returns. Including the chassis.
2/ Connect the "grounding terminal on the VertaMax enclosure" to the vehicle chassis, your green wire.
3/ The inverter doesn't have to connect to mother earth ground. Your yellow wire.
4/ There is no proven requirement to wire a solar panel frame to the Van Vehicle. I guess there could be a very large system on a very large vehicle.
5/ If you are planning to plug into a grid with a shore line, the chassis must be connected to the mother earth ground with the green wire.
6/ Never bond the white neutral to anything but the shore cord white neutral wire.
7/ Always check that the pedestal for your shore line has a quality green, mother earth ground, connection to the entry panel from the grid.
I have never had anyone call our plans a "small system" before. We've been told that we are on the low end of large for an RV.
#1 I will move the ground wire to the other side of the battery monitor shunt. Thanks.
#3 my yellow wire - in not a ground wire. it's the wire for the 30 amp outlet.
#5-7 Our travel trailer's existing electrical system is factory installed and has it's needed grounding wires when plugged into the power pole at the campground. We're not touching any of this stuff. None of the wires in my diagram are part of the RV's existing electrical system. I'm just talking about plugging the shore power cord into the 30 amp outlet that we intall on the inverter and getting our power to the RV from there when we are boondocking.
 
These two items seem to conflict.

● The charger must not be connected with grounded PV arrays. (one ground connection only)

· Ground the frame of the PV panels. We have 8 panels: 2 pairs are mounted together. This sounds like I need to ground the 4 separate panels and the 2 pairs, 6 grounding points all together. Ground them to the chassis.
The manual also says " ● The plus and minus of the PV array should not be grounded. Ground the frame of the PV panels to reduce the impact of lightning." As I understood the manuals description, they are referring to not grounding the positive wires coming from the PV array and not the frame of the panels.
 
  • Like
Reactions: Dzl
The manual also says " ● The plus and minus of the PV array should not be grounded. Ground the frame of the PV panels to reduce the impact of lightning." As I understood the manuals description, they are referring to not grounding the positive wires coming from the PV array and not the frame of the panels.

That makes sense. On my trailer, the frames of the original solar panels were not grounded, so I didn't ground the new panels either.
 
#3, sorry, I missed that. Probably I was expecting three wires from plug to inverter and did not bother to read your labels.
#5,6,7. Always is good to check stuff.
 
Victron is referring to taking the negative lead from the PV array and grounding that? They aren't referring to grounding the panel frame? That seems confusing.
Victron--a company Ilike-- has atrociously vague and (possibly poorly translated) grounding advice in a lot of their documentation. And generally will not clarify or advise on their support site due to liability concerns. While I understand this, pretty much every other top tier manufacturer gives explicit but generalized guidance (to be fair, we (North America) are a secondary market for Victron, and a primary market for many of the other top tier brands)

I started a thread on trying to understand the language on grounding in the smartsolar manual a while back. I did not get a good answer in that thread, and did get some wrong ones, but it may be worth reading through anyways. I started another thread on the same topic but more generally related to grounding and dual pole breakers here. This post over at AZ wind and sun is tangentially related
Why? On a vehicle? I agree on a S&B.
A question I have often wondered. Context is often the missing component in our discussions on grounding.

Because PV panels are current limited to Isc, and because a short to ground or to anything else can't trip OCP, is it reasonable to infer that the purpose of grounding PV arrays has nothing to do with shorts/faults and more to do with lightning and dissipation of static charge?

In either case, It seems like the panels will usually be grounded by default, actually I'm going to take that back mid sentence. They would be grounded by default if attached to the metal roof of a vehicle, on a boat or RV or fiberglass camper shell they may not be bonded to the vehicle body/chassis


As to your general questions (OP) here is a simple diagram from Victron Wiring Unlimited showing a basic typical offgrid installation, it illustrates how you can properly ground your component cases with Equipment Ground Conductors (EGC's) while only having one bond between your system and chassis or earth ground:

Screenshot_2020-04-23 Wiring-Unlimited-EN pdf.png


There is no shunt shown, but as @Zil mentioned, it would usually go between the battery negative and everything else. An important distinction to understand is equipment grounding vs system grounding. Equipment grounding is the concept of connecting the not-normally-energized parts of electrical components (such as metal cases) back to the designated grounding point and DC negative. System grounding is the single connection between your system and earth or chassis ground (in the example above the ground symbol to the right of the battery is the system grounding point, the green wires between inverter and the system grounding point, and the smartsolar and the system grounding point are EGC's)

This gets confusing because usually people just talk about 'ground' and 'grounding' without differentiating between the two. I think our lack of clear language makes the topic more confusing than it needs to be. I should note, I am far from an expert. Just a beginner who has tried hard to research and understand grounding.
 
In my search for a new RV, I've been on or poked my head onto a lot of roofs. I have yet to see a solar setup with a wire running from the PV panel frame to a ground. I'm not saying that's right, just that it's very common.
 
  • Like
Reactions: Dzl
In my search for a new RV, I've been on or poked my head onto a lot of roofs. I have yet to see a solar setup with a wire running from the PV panel frame to a ground. I'm not saying that's right, just that it's very common.
@RandyP has a copy of the RV electrical guidelines, if he is still around on the forums he might be able to shed some light on whether the guidelines give any guidance on this topic. But I agree, anecdotally, I can't recall seeing actual EGC ground wires on small mobile PV systems

But logically, with the limited info I have, I think Zil's answer makes sense. What works for a fixed structure (or even a boat) does not always translate to a mobile system.

Speaking only for myself, its very possible there are factors I am overlooking or not aware of. The inclusion of a GFPD is one possible factor (but most people seem to skip this too).
 
I do have the RVIA / LV ANSI standard somewhere around here. Just Cannot find it right now. Wish I could.
I think Solar panel equipment grounding should be done. I have not seen it done on mobile equipment, but think that it should be done. Maybe I can find my copy of that standard soon.
I think the answer lies in other ANSI, NFPA standards for solar panels. The RVIA / LV standard is a short document, dealing mostly with a 12v mobile electrical system.

But do note that grounding a solar panel metallic frame in any way will not change the lightning protection for the mobile equipment. If the solar panel frame is effected by lightning strike, it will be burned up along with the mobile equipment. Lightning protection is laid out in another NFPA standard, it has to do with grounded discharge points around the equipment to be protected from lightning. These discharge points are generally located higher above earth than the protected equipment and are isolated from the protected equipment.
 
Here are a few of the grounding wiring diagrams for Magnum Power equipment. This first one is for a PT-100 SCC device. Not the PT-100 includes a internal GFDI2 device (Ground Fault Detection Interuption device). This drastically changes the system grounding wire diagram.

elec system ground pt100 jpg.jpg
______________________________________________________________________________________________

Heres another Magnum grounding wire diagram, this time for a smart hybred inverter, including AC and DC grounding.

elec system ground MHS M jpg.jpg

As you can see, there are very specific instructions given by mobile electrical equipment manufacturers. I would suggest you follow the instructions given by the equipment manufacture you are installing.
 
  • Like
Reactions: Dzl
I completely fail to see how a mother-Earth Ground could have any relation to any vehicle DC or inverter system. The only time mother-Earth Ground would be relevant is when plugged into a grid electric supply. My inverter has a GFCI outlet. It refers back to the inverter case. The case of the inverter is connected to the chassis and battery negative.
 
Only mother nature would know what a 'mother earth ground' is.
 
I completely fail to see how a mother-Earth Ground could have any relation to any vehicle DC or inverter system. The only time mother-Earth Ground would be relevant is when plugged into a grid electric supply. My inverter has a GFCI outlet. It refers back to the inverter case. The case of the inverter is connected to the chassis and battery negative.
Consider pass thru inverters with smart hybrid features. Power is taken from the battery under certain conditions and inverted to 120v ac in sync with the shore power 120v ac to supplement loads greater than the shore power can accommodate. In this case the shore power supply is providing the N to G bond with grounding electrode (earthing ground). The inverter continues to isolate its neutral to ground connection because the shore power is providing the N to G bond and earthing. There is only one N-G bond allowed in ac electrical systems per the NFPA/NEC.
 
Last edited:
  • Like
Reactions: Dzl
In this forum, as in most, one must differentiate between the use of the word "ground" as so many use it to mean the negative side of a dc circuit. So "mother-Earth Ground" should help some of the confused muthers around here. :)
If RandyP would go back and read the second sentence in the post he quoted. He may notice that is what I said.
I do know "pass-through inverters" in RV use. They pass grid power past the inverter to the RV and also charge the battery. But it must be a very expensive unit that will do more than pass grid power to the RV and charge the battery. Can any one link to a unit that can synchronize the ac side of the inverter with the grid cycles?
 
In this forum, as in most, one must differentiate between the use of the word "ground" as so many use it to mean the negative side of a dc circuit. So "mother-Earth Ground" should help some of the confused muthers around here. :)
If RandyP would go back and read the second sentence in the post he quoted. He may notice that is what I said.
I do know "pass-through inverters" in RV use. They pass grid power past the inverter to the RV and also charge the battery. But it must be a very expensive unit that will do more than pass grid power to the RV and charge the battery. Can any one link to a unit that can synchronize the ac side of the inverter with the grid cycles?
Magnum MHS 3012 M inverter/ charger. I think Victron has a few also.
Here's a little info about the magnum product:
You may have to restart the video at 0 to get the whole message.

I think that when you say "mother-earth ground" you are referring to the Grounding Electrode (GE).
"• Grounding Electrode (GE): A conducting element that establishes an electrical connection for
a common ground reference. In vehicles, it is usually the chassis or frame; in vessels, it is the
largest metal item onboard, usually the main engine frame."
And in a sticks and bricks setup, it is sometimes a copper clad steel rod driven into the earth, about 8' long.

System grounding has been cussed and discussed for many years. Terminology has evolved, that if learned by all and used consistently, puts us all on a level playing field. Inventing new terminology could just be counter productive, in my honest opinion.
 
Last edited:
Back
Top