I don't understand Grounding

[BradKW]

On a house, we drive a 6 foot metal stake into the ground to give current a safe place to go...I get that. 

On a vehicle I'm running ground wires to the frame that is sitting on 4 rubber pads, effectively insulated from the ground. What's the point?

When I Google vehicle grounding, I see cautions about false ground loops, floating grounds, and electrifying the vehicle frame by mistake. 

I have a battery bank, Inverter, and Charge controller that all want me to run grounds, and I'm back to confused again   :/

 

[Goshawk]

There are many types of ground. http://www.arrl.org/grounding


Sent from my iPhone using Tapatalk

 

[minimotos95]

Household A/C "ground" to the earth for safety, Vehicles DC "ground" to the chassis/body is to save wire for the most part.

Most simplistic explanation. I am sure someone who knows more fine details l will inform us exactly why that 3rd prong and ground post became standard in S&B

I always go to the - terminal when I can instead of ground.

 

[GotSmart]

The simplest way to put it, was to keep people from being electrocuted.

 

[speedhighway46]

If you are only dealing with DC voltage, one wire to positive and one to negative (ground); no problem.

The problem is understanding AC voltage and how to wire it, as it is different for "homes" than it is for vehicles.

In simplest terms; AC wiring in a house has the grounds (green wire) and the neutrals (white wire) tied together at the service panel, and then grounded via a long copper clad stake driven into the ground.

In a vehicle, obviously, you cannot drive a stake in the ground. So you must protect the vehicle from a potential ground short of the neutral side of the AC circuit. This is easily done by what is termed "floating neutrals". In a nutshell, at NO PLACE IN THE CIRCUIT can the white neutral wires be tied to the green ground wires. The point where they do combine is at the shore power service panel.

I suggest you search the National Electric Code for a more indepth explanation; under "floating neutrals". Also search the archives here as this topic has been discussed before.

Hope this helps.

 

[Trebor English]

Post #3 by minimotos95 nailed it. Vehicular ground is to use the body/chassis for 1/2 the wire. Electrocution is a thing with 120 volts, not 12 volts. With 12 volts the necessary wire size is large therefore expensive. Cutting out most of the minus side wire saves the cost of copper.

 

[BradKW]

The simplest way to put it, was to keep people from being electrocuted.

That's how I always understood it...give the current an alternative path if the appliance "housing" becomes electrified. But in a vehicle, I don't get what the alternative path is, since there's nowhere for it to go to ground..?

 

[BradKW]

Post #3 by minimotos95 nailed it.  Vehicular ground is to use the body/chassis for 1/2 the wire.  Electrocution is a thing with 120 volts, not 12 volts.  With 12 volts the necessary wire size is large therefore expensive.  Cutting out most of the minus side wire saves the cost of copper.

I've read that, and since I've run a full neutral circuit with wires to everything, it makes me think I don't have to ground. But then I think that doesn't sound right either...  :/

 

[Every Road Leads Home]

You can always get a very long wire and ground it to the house stake.

 

[IGBT]

I think the reasoning in a RV or van or other vehicle that you may want a 12V return wire (ground) that is an actual wire and not just the vehicle chassis is for resistance.  The chassis could have rust or paint or some other issue that causes it to be a higher resistance path.  If you have a copper wire for the return (ground) wire you know what the resistance is going to be. 

By tying the vehicle chassis to the negative terminal of the battery at the battery, in addition to having a 12V positive and 12V return wire going to each appliance, you now guarantee that a short in your wiring will trip a breaker or blow a fuse instead of possibly damaging one of your appliances or causing a fire.   If the chassis is left floating, not connected to anything, then a nick in a 12V wire that touches the chassis will energize it to 12V.   Now an appliance that has it's case internally connected to the ground on it's circuit board will get 12V on the circuit ground and may go poof or in a really bad case start a fire.   If the chassis had been connected to the negative terminal at the battery, with a beefy cable, then likely the nick in the 12V wire that shorted against the chassis would trip a breaker or blow a fuse instead of frying your appliance or starting a fire.

 

[Gary68]

here is the way i understand it,on dc(edison),it flows like water,the positive needs a reason to flow,opposites attract,the ground is actually a negative attracting the positive to flow

ac(tesla) does not flow,it moves back and forth and the ground is there for safety,if there is a short the electricity goes to the rod and into the ground and doesnt electricity the appliances

 

[Mobilesport]

I've wired 12 volt vehicle electronics for over 20 years and reading some

of the posts in this thread confuses the hell out of me too.

The reason why it's confusing is because alot of people
are overcomplicating something thats so simple .

Wiring 12 volt electronics is super simple ,

1: forget everything you know about wiring a residential house.

2: battery has a red positive post and black negative post.

3: all 12 volt components such as invertor,  car stereo TV etc. Etc. have a red wire and a black wire.
To power any 12 volt component just run its red wire to positive battery post and black to negative 
battery post  .
red wires should have appropriate fuse inline the red wire close
 to the battery.
Use proper gage wire.

4: just think of the chassis ground as a big wire that you can use if you
want to . See the picture that I posted.
Look in the picture and you'll see 4 ground wires going from the
components and all that the chassis is doing is completing the
ground circuit. I could wire these 4 components like in the picture with my 
grounds running through the chassis or I could run them 4 wires to the
negative side of the battery,  either way I would accomplish the same goal which is positive  to
positive and negative to negative 


That's how simple 12 volt electronics are , run red wires to positive battery post and
black wires to negative battery post , use the chassis if you want to ,,, that is it.

As for the 110 volt appliances, ,,, simply plug them in , sometimes using a 
extension cord or a power strip.

 

[Mobilesport]

I forgot to mention that some components don't draw many
amps like led lighting and then there's components that draw 
high amps like fans and water pumps , low amp components very
simply red to red and black to black.

High amp draw components like fans and water pumps require a relay.
Here's a picture of how to simply wire a high amp draw component .

 

[frater secessus]

I have a battery bank, Inverter, and Charge controller that all want me to run grounds, and I'm back to confused again   :/

Thanks for asking this question, Brad.  I've been having periodic "shower thoughts" and reading the responses has been informative.

Ordered used copies of Moeller's RV Electrical Systems and Calder's Boatowner's Mechanical and Electrical Manual but they haven't arrived yet.  I've seen them both recommended for DIY RV folks.

 

[Optimistic Paranoid]

As for the 110 volt appliances, ,,, simply plug them in , sometimes using a 
extension cord or a power strip.

Except that your chassis and body really need to be connected to the third (or safety ground) wire of any ac coming into your vehicle to protect against a potentially fatal "hot skin" condition.  See:

https://www.amazon.com/No~Shock~Zon...TF8&qid=1487530782&sr=8-2&keywords=Mike+Sokol

 

[BradKW]

I forgot to mention that some components don't draw many
amps like led lighting and then there's components that draw 
high amps like fans and water pumps , low amp components very
simply red to red and black to black.

High amp draw components like fans and water pumps require a relay.
Here's a picture of how to simply wire a high amp draw component .

What's a relay exactly, and why do they need it? And what happens if it isn't present?  ty....

 

[Mobilesport]

What's a relay exactly, and why do they need it? And what happens if it isn't present?  ty....

The relay is put into the high amp draw circuit to protect the on / off switch,  if there 
was no relay in that circuit the water pump would draw amps from the battery and when
those high amps flowed through  that on off switch the switch would burn up..
I've had times of when I wanted to pump fuel out of a gas tank using a 
inline electric fuel pump , I would run a positive and a negative wire from the
fuel pump to a battery using alligator clips , in this case I used no
relay because there was no switch or other electronics to protect , just using that as a example. 

You should download that picture I posted of how to wire a relay and keep it for reference , any time you
want to wire up something that draws alot of amps like , flood lights , fan , water pump etc. just use that picture and just wire in your high amp draw component to were I have the water pump in the picture.

 

[Mobilesport]

Except that your chassis and body really need to be connected to the third (or safety ground) wire of any ac coming into your vehicle to protect against a potentially fatal "hot skin" condition.  See:

https://www.amazon.com/No~Shock~Zon...TF8&qid=1487530782&sr=8-2&keywords=Mike+Sokol

Does this pertain to generator and invertor or just shore power ?  Thanks

 

[ArtW]

I'm no expert on this, but my old Travel Trailer explicitly says in the owner's manual to make sure the tongue jack rests directly on the ground if possible
I don't recall seeing this in the manual for the Shasta, but the Road ranger was wired with totally separate 12 and 120 systems that had no connection to one another
full disclosure, the manual for the Shasta is much fatter, and I skimmed it rather than really reading it, the way i did the manual for the RR

 

[Gary68]

damn you brad,make me go reading sternwakian stuff from guys with letters after their name but in fact a 12 volt system has no "ground" it doesnt  go to the ground/earth,something about old times,not understanding electricity and since the term is used in ac they incorrectly used it for dc and it stuck,i think it should referred to as the "common"?

looked at a few sites,heres one,have fun
http://electronics.stackexchange.com/questions/123906/ground-vs-earth-vs-common-vs-negative-terminal