Grounding a solar system - What parts do I ground?

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poot_traveller

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I've tried looking on google and YouTube for an answer, I also tried the search function on this forum - still nothing.

So I'll ask here; What parts of a solar system do I have to ground?,  I know the inverter has to be grounded because it says so in the instruction manual.  But what about the controller, battery and panel?
 
The common wisdom is to ground the negative battery terminal, plus any devices that have a grounding terminal, to the vehicle chassis. However, if you are bolting the device directly to the chassis (through a hole in a metal part of the device's body), as I did, then it is already grounded. The point is that the body of the device should be grounded to the chassis, for safety purposes. The ground connector is there for those times when the body of the device is not already connected to the vehicle chassis, such as when you mount everything on a board. Sometimes people will use a single point on said board as the common ground, and then connect a single, heavier wire from there to the vehicle chassis.

Remember: "ground" is NOT synonymous with "negative" despite the some poor instructions you may find on the internet. The ONLY negative terminal in the whole system that should be connected directly to the vehicle chassis is the negative battery terminal. Don't other negative terminals connect to this? Yes. But do not try to connect those to the vehicle chassis separately. Many instructions will tell you to just connect the negative terminal of lights and things to the chassis and the electricity will find its way back to the battery via the vehicle chassis. This is not considered best practice. It is better to spend the little bit of extra money to run that additional wire all the way back to the battery. 

Grounding to the vehicle chassis should only be for safety purposes.
 
The instructions that came with my inverter say: "On the rear panel of the inverter is a terminal fitted with a nut for connecting to the inverter and to the earth terminal of the AC output socket. Connect the inverter to the chassis of the vehicle."

So I assume I have to connect a earth wire running from one terminal to the other on the inverter. Then run a earth wire from one of the terminals on the inverter, (the instruction manual doesn't say which terminal), to the chassis.

I'll also have to run a earth wire from the negative terminal of the battery to the chassis. That means two earth wires.

What AWG should the earth wire be please?
 
No parts of any solar installation I have built have been connected to "ground". Two wires from the panel/s to to a controller or DC to DC then two wires from the output of the device to the battery. My VW uses a chassis return for the starter battery. The native electrical system uses this chassis return. All loads on the house battery are twin wires to the item to be powered.

Have never grounded an inverter case. Unless you are using the inverter through a RCD or ELCB protection system, I cannot see any reason for grounding an inverter. Same comment in the case of connecting an earth stake to a petrol generator. If you are concerned, seek advice from a licenced electrician who knows the AS/NZS3000 regs.
 
Grounding is one of the most misunderstood concepts of electrical wiring, even among professional electricians.

On the DC side, grounding refers to running a wire from the negative battery terminal to the chassis of the vehicle. On cars, vans, trucks, etc., this is done primarily as a cost saving measure, allowing the vehicle manufactures to run one wire for every device rather than two.

On the AC side, the ground wire serves two basic functions.

The first is to protect the electrical system from excess current induced into the wiring from a lightning event by providing this excess current a path to the Earth. This is why buildings have grounding rods pounded into the ground where power enters the building. Take note that I said a lightning event rather than a lightning strike. A lightning event is lightning strike in the general area, close enough to induce current into electrical systems. A lightning strike is a direct hit and will fry a building's electrical system regardless of whether there is a grounding rod present. Both of these are largely non-issues when dealing with an AC power system on a vehicle. The vehicle's tires insulate the vehicle from the ground, making a grounding rod unnecessary.

The second purpose of a ground wire is to provide a path for the AC power to flow back to it's source in order to trip the breaker or blow the fuse when something short circuits. In this case, the inverter you install on your vehicle is the source, so all your wiring needs to have three conductors. You Need a Hot, which carries electricity to your devices, appliances, etc. This wire is usually, but not always going to be black, red or blue. Next you need a Neutral which is a path back to the source. This wire should be either white or grey. Finally, you need a ground wire, which should be either green or bare copper. This wire is not needed for your electrical system to work, but is an important safety feature. It will provide a path for the electricity to get back to the source (inverter) to trip the breaker or blow the fuse in the case of a short circuit. It will also trip the breaker or blow the fuse if the Hot wire comes into contact with the metal housing of whatever device you have plugged in, possibly saving your life. Sure, it's annoying having the breaker trip or the fuse blow, but I'd much rather have that happen than get electrocuted because my toaster had a frayed wire making contact with the housing.

Now with all this said, you really should run a wire from the ground post on the inverter to something metal on your vehicle. Once you've made that connection, your vehicle's body, frame and chassis components will become a path for the electricity to trip a breaker or blow a fuse. Once again, this could keep you from getting electrocuted when you go to open your door after the exposed wire you didn't notice on the extension cord running out your window gets blown into a lug nut by the wind.
 
brahmon said:
good.  i didnt ground anything either.
It is a lot safer that way.   The only way you get electrocuted by a non-grounded/earthed inverter is to hold a bare wire in each hand then stick one of the wires in one hole in the output socket and the other wire in the other hole while the inverter is powered ON. You need to insert yourself in the return path between active and neutral from the inverter. Less than 100mA at 230 Volts is deadly. RCDs and ELCBs as human safety protection devices trigger at less than that and faster than one cycle of AC, but quadruple your installation costs over a simple two wires from a battery to an inverter to an AC powered device.
 
I've been running my solar for six-plus years without it being grounded. I figure it's like a big solar charged flashlight or any other portable DC appliance that runs fine within its own circuit, with no external grounding.
 
I've counted up the votes, and half of people across the different forums and sub reddits say to ground the system. The other half say don't ground anything.

I guess there is no real right or wrong answer.

Since I'm only using the solar system to charge a laptop and 12V/12AH kontiki batteries, I've decided to not ground anything.
 
As Sephson said [Excellent post on the subject. I started to post and gave up.] , there are two "grounds" involved. The vehicle chassis is not connected to earth or "ground", unless it has those static discharge feelers. A vehicle can build a static charge. A grounded person touching the vehicle can receive a shock. It 's why the toll booths have a thin wire rod that contacts the vehicle before it gets to the booth.

The chassis is used as a DC negative bus. It is not a "ground", it is 12V-.

An inverter has a third smaller terminal that is to be connected to "ground". In a sticks and bricks off grid setup this could and should be done. In a vehicle I don't know what it is supposed to do or even where it should be "grounded".

If every plug you use has only two prongs then the inverter ground might be irrelevant. Plugging in a three prong plug such as on a hand drill, etc. might be different.
 
The battery and inverter aren't touching any metal parts of the campervan.  The battery is on a plywood floor, and the inverter is going to also be attached to plywood.

The inverter AC plug is three prong.
 
I hate getting shocked. Electricity has reminded me a few times why I need to respect it. I had a 12 volt shock once from a 28AH bank that broke the skin and bled across the 2 contact points. 3 amps @12 volts is widely regarded as a lethal shock.

36 watts to kill a person. That's pretty deep if ya think about it. Incandescent bulbs were mostly 40 or 60 watts. 60>36. You cant be negligent with electricity and expect safety.

That being said, I wouldnt ground a 12v DC circuit other than the negative battery terminal to the chassis.

An AC inverter I wont likely chassis mount for a multitude of reasons. 
A: the AC would see intermittent usage only and mostly with 2 pronged devices.
B: Its not an unlikely event of there being some sort of "noise" or other interference between an AC and DC system sharing a common ground. Especially with a cheap knock off Chinese inverter. I'd hate to fry the vehicles computer with some sort of spike from my $29 inverter.

If I were installing an inverter in an off grid shack I WOULD ground the inverter but not the DC system. I'd drive a long copper spike into the earth and tie the inverter ground lug into it.

My 2 cents.
 
The AC will see use with only 3 pronged devices (our plugs here are mostly 3 pronged, except for cell phone chargers). I assume that's what you mean.

Yes I'm going to ground the battery negative to the chassis. What AWG wire should I use? 6 AWG?
 
I'm new here and realize this is an old thread, and I'm not trying to be annoying, but I feel compelled to ask, because I do not understand basic vehicle electrical. I purchased a Uhaul, and I put solar panels on the roof, and I'm using a Bluetti portable power source. It has the option of grounding to the chassis. But my question is, isn't the car battery under the hood also grounded to the chassis? What are the consequences of having two separate batteries grounded to the chassis? Are the batteries now in parallel? What happens if you want to put led lights, and wire them to the car battery and not your solar (or vice versa), and put the negative from the led lights to the frame rather than run two wires. Is that a problem having two batteries share the same ground? Does the electricity go to the right place? Lastly, if both batteries are sharing the same ground, can I use the accessory wire from the car battery, constant power from the solar battery, and the black wire spliced into the black wire from head unit to keep a hardwired dash cam running 24/7?
 
The answer is easy, the house battery does not have to be grounded to the chassis.
 
It’s like having 2 different circuits grounded to Earth. There are millions of circuits using the same ground - the Earth.

However grounding to the same chassis with those separate batteries I would want some fuses properly located for separation protection in case of one of the circuits shorting and maybe affecting the other……

INTJohn
 
I keep house and vehicle circuits separate so as not to discharge the vehicle battery while parked. A circuit requires both a positive and a ground connection be made in order for it to work. You can connect as many ground wires as you want as long as the positive posts of the two batteries are isolated from each other there will be no circuit (path for the electric to travel).
 
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