Truck mounted shelter grounding questions

[quickfarms]

When using a grounding rod, you may want to drive it at an angle so that it can be pulled out using the vehicle when leaving. Don't use a ground rod when hooked up to the utility co service, one or the other, not both.

Why not use an additional ground when hooked to utility power? Every sub panel is required to have a grounding rod. There is an issue with grounding the neutral when you are using a GFI and with certain wiring.

 

[cranetruck]

Why not use an additional ground when hooked to utility power? Every sub panel is required to have a grounding rod. There is an issue with grounding the neutral when you are using a GFI and with certain wiring.

Intuitively I'm thinking there is something wrong with multiple grounds, say if the house becomes grounded via the puny ground rod by the van exclusively for some reason, but I'll check into the facts and come back to you.

 

[Aswayze]

More grounds is fine. In robotics, we put ground rods all over the darn place just to quiet things down and get rid of kooky signalling issues.

If it was me:

Rely on "Shore Power" to provide the ground when on an RV hookup.

Drive a ground rod at the gen when running off the gen.

 

[C Big]

BTW jw4x4 I know a guy who remain nameless that had neighborhood kids that would not leave his truck alone after numerous warnings, he hooked it up to a solar fence charger. They don't play on his truck anymore.

I worked at this place where we had to park next to a lot that had a basketball goal in it. The local teenagers would play "street ball" they were always sitting on our cars and sitting in the back of our pickups so I got the bright idea to hook up a 12 volt electric fence charger. I drove a ground rod in the ground installed a remote on/off, locked it in my trunk, turned it on and walked away. When I came back all the windows were broke out and the tires were cut. I bet it would have been funny to watch, but I think one of them took it personally. Was pretty expensive. They did stop sitting on our cars though.

 

[KsM715]

I like it.



But a fence charger is DESIGNED to NOT be lethal. High voltage, very low amperage.



120v circuits kill people on a pretty regular basis.





That's about 4 people per day, and that's JUST for consumer products. It doesn't count deaths when working on house wiring, for example.


Ground that sucker.

I can not count the number of times when working on something I'll ask where the breaker is or ask if the circuit is off. It never fails, some smart a$$ contstruction worker will pipe up and say "why, its only 120?" but the same guy will absolutley refuse to grab onto the wire when I offer him one end and ask him to just touch it.

Yes, you can get shocked by 120 a hundred times and not get hurt. You can also get shocked one time and stop your heart dead.

 

[steelandcanvas]

Every sub panel is required to have a grounding rod.

NOT TRUE! Electrical sub panels are required to have the Neutrals (grounded conductors) isolated from the grounding conductors. Grounding is done at the Service Entrance or Main Panel. DO NOT install or connect to any other ground rods when connected to the utility, all grounding MUST be done at ONE point. FIX the problem with the shelter, DON'T try and put a band-aid on it.

Also Gentlemen, it's not the voltage that stops your heart, it's the current. In the right conditions, 1/10th of 1 amp can stop your heart. Anybody that says "it's only 120 volts" is a Moron.

More grounds is fine. In robotics, we put ground rods all over the darn place just to quiet things down and get rid of kooky signalling issues.

You are most likely "bonding" to eliminate stray signals, not grounding...two different tasks.

 

[MarcusOReallyus]

Yes, you can get shocked by 120 a hundred times and not get hurt. You can also get shocked one time and stop your heart dead.

In the right conditions, 1/10th of 1 amp can stop your heart. Anybody that says "it's only 120 volts" is a Moron.

I've taken 120v across my chest, from one hand to the other. That's about the worst configuration for 120v, as it goes right across the chest. I thought I was working with 12v on a boat. Didn't know there was shore power riding on the same bus. I'm here to tell about it. It got my attention, but that's about it.

But I'm not stupid enough to let that one rare instance make me think I can be careless with 120v. I treat it VERY carefully. In fact, I've been called a sissy for being careful. (Double checking breakers, checking my self when I think there's reason to not trust someone else's word, etc.)


That's not being a sissy. That's being NOT STUPID.


For reasons I'll never understand, some people equate being stupid with being manly.

 

[steelandcanvas]

Marcus: I have also taken 120 Volts from "hand to hand", that's an experiance I don't want to repeat. It was "homeowner" wiring, somebody ran the Neutral through a switch to the garbage disposal, instead of the Hot. I saw the switch was in the OFF position and continued to reinstall the new disposal. BAM! I was lit up for what seemed like hours. My bad, I didn't take my Fluke and check the Hot to Ground, just Hot to Neutral. That was years ago and now I'm like you, checking everything twice. Call me a Sissy, but you won't get the chance to call me a dead Sissy.

 

[zout]

The purpose of using a ground rod on a service is for lightning protection not to handle fault current, the ground wire is bonded to the neutral at the point of service so fault current has a good solid low resistance path back to the point of generation. The ground rod will provide a path but it will be high resistance and vary depending on the moisture in the soil, the ground rods most important job is the help with lightning protection because the point of generation is the earth not the generation plant. When you are running your generator it is the point of generation so the ground wire and frame should be bonded to the neutral at that point. When you are shore power the separate ground wire not neutral will go all the way back to the point of service where it's bonded to the neutral and ground rod for a good fault current path. So no you don't need a ground rod unless you are worried about lightning and then you don't want to be the best ground around anyway, your tires are good insulators and just put plastic or wood pads under your stabilizers to help isolate the rig from the ground and enjoy.

 

[quickfarms]

NOT TRUE! Electrical sub panels are required to have the Neutrals (grounded conductors) isolated from the grounding conductors. Grounding is done at the Service Entrance or Main Panel. DO NOT install or connect to any other ground rods when connected to the utility, all grounding MUST be done at ONE point.

Where did you find that in the National Electric Code?

They require a grounding rod on each separate structure in most cases. Additionally the grounding rod needs to be 8 feet in length.

Please read the code.

 

[AN/ARC186]

And now a few words from an Electrical Inspector,
1) if you have current between earth and the metal of the shelter then you have a problem, installing a ground rod will just shunt that current to the earth. Find out what is causing the issue.
2) a vehicle mounted shelter is NOT considered a separate structure, it falls under the rules for RV's and the like, there is no requirement for a supplemental ground rod for the electrical branch circuit supplying the shelter.
3) The cabling supplying the power to the shelter should provide the grounding path for the shelter when on shore power.
4) You should under no circumstances "leave it like that" you'd be setting yourself up for more trouble than you can imagine.
I can send you all the applicable articles from NFPA 70 if you PM me.

 

[tim292stro]

The purpose of using a ground rod on a service is for lightning protection not to handle fault current, the ground wire is bonded to the neutral at the point of service so fault current has a good solid low resistance path back to the point of generation...

No that's incorrect, and this mis-information is especially dangerous if the circuit you are referring to gets its power fed by a transformer (like most homes) or a generator (like most remote camp sites). The ground rod is an essential part of maintaining a reference voltage at a low-level - a transformer feeding a residential load, or a generator powering a remote load must have a REFERENCE to a known potential, otherwise it's floating to an unknown voltage. We drive a ground rod under NFPA 70 to a low impedance load to bring the "0-volts" potential to a level in reference to the environment around the circuit. This is an important distinction, and is why you can get shocked by a truck that has an improper ground on an AC circuit - if its reference potential vs the actual ground you walk on is higher than the voltage required to jump through your skin barrier, you can even get shocked by the neutral. On the home-side of a residential power transformer, the power company may install a ground rod at or near the pole, but you are also required to place a rod at or very near your Main-Point-of-Entry (MPoE) to reference your home to the local ground - your power company may vary in its ground to neutral bonding practices, but in general it's done in the meter box or at the main breaker (before the breaker). [EDIT 2:] I should also point out that NONE of the standard services provided by power companies include a ground wire. Go out and look at your power feed on your home - if it's single phase, you have two hot black wires and one bare conductor - that bare conductor is the neutral, not ground, and it's just a center-tap of the transformer (120 below and 120 above - giving you 240 across the black wires). On three-phase Delta, there are only three black wires no neutral is provided typically, and certainly no ground. On three-phase Wye, there are three black hot wires and one neutral, and this neutral is usually not bare - but still no ground wire. [/EDIT 2] Outbuildings need a separate grounding-rod/electrode under the '08+ code, but you should not have a second ground-neutral bond at the sub-panel as this WILL create a parallel current path with your neutral from the main panel to the sub panel (loop is between the two bonds). If you feed the sub-panel with a GFCI, it will trip constantly (probably never allow you to reset it either).

Neutral is a current carrying conductor, while ground is a fault carrying conductor.

The point of GFCI is to identify if current which is sent out over a hot is completely returning via the neutral (single-phase systems) or the other hots (three-phase systems). If a GFCI device detects that more than 6mA or 20mA are escaping (depends on the type of circuit, residential is 6mA, commercial with motors is 20mA), the GFCI device will open the circuit to stop the flow of power. Obviously in a system like this you want to have a ground WIRE going to the outlets from your load-center/breaker-panel, but you still need the ground rod, and neutral bond to reference the supplied voltage to the local conditions.

The ground bond in every metal box and conduit is intended to "capture" the return current from a bare wire to the ground reference - this prevents the box from becoming energized and potentially arcing to an object outside the box, which could kill someone or cause a fire (and this is really why NFPA is the group doing the NEC).

The added bonus you get from bonding everything and providing multiple ground rods around a facility are better containment of RF emissions from the electrical system. The military has know of this for some time, as to most HAMs.

...The ground rod will provide a path but it will be high resistance and vary depending on the moisture in the soil, the ground rods most important job is the help with lightning protection because the point of generation is the earth not the generation plant. When you are running your generator it is the point of generation so the ground wire and frame should be bonded to the neutral at that point. When you are shore power the separate ground wire not neutral will go all the way back to the point of service where it's bonded to the neutral and ground rod for a good fault current path. So no you don't need a ground rod unless you are worried about lightning and then you don't want to be the best ground around anyway, your tires are good insulators and just put plastic or wood pads under your stabilizers to help isolate the rig from the ground and enjoy.

This is an NFPA 780 system, and yes it will need a ground rod (several usually) as well as a a bond to your electrical system's ground and any structures in an area are expected to be bonded, and you may need to install a ground grid if the soil requires it - they are most worried about the step voltage with lightning, meaning there can be enough voltage potential across the ground just by taking a step, that you can have several thousand volts from foot-to-foot (and zzzaaaapppp!!!!). It's also why they want you to tie in chain-link fences and other things into your lightning protection system.



MWMULES - if you're getting a good jolt from the shelter when you touch the shelter while touching something which is grounded, you probably have another fault you want to locate, so turn the power off first. I'd suggest first, installing a ground rod locally (nearest to the shelter) and grounding the shelter to it. [EDIT:] In the post above, AN/ARC186 represents himself as an electrical inspector - under his item #2 he is correct that there is currently no requirement for a ground rod for an RV - but I feel I should give that an additional context: If you are running HAM gear inside the shelter to an antenna outside the shelter, you need that ground (probably many actually), and you should know this if you are a HAM. Adding a non-required ground rod to an RV or temporary shelter while powered by shore-power is not a safety reducer - and if your shore power connection is long, or travels over various soil condition changes which affect the soil's conductivity, you SHOULD install a ground rod to match the ground conductor to the local ground conditions of the shelter [/EDIT] If you are feeding the shelter from shore power at your home, first check how that's being done, it could open a can of worms. You are required to have a neutral and a ground conductor from your main panel to any sub-panels, if you don't have that - it's your first issue. You should also be feeding any outdoor circuits with a GFCI, if not that's your second issue. If you are using temporary power cabling to power your shelter (the NEC term for "extension cord"), check that first visually, then with a multi-meter to make sure it's not shorting out anything. Back at your shelter, MAKE SURE YOU DON'T HAVE ANOTHER NEUTRAL/GROUND BOND, if you do the GFCI feeding your shelter shouldn't let you have power and if it does it should trip immediately. Having a neutral/grond bond on a sub-panel, like the inlet from "shore power" in a shelter powered by a home, will turn your shelter into a neutral conductor (not ground). This is especially dangerous if someone f-d up the wiring in the feed to your shelter and swapped neutral and hot (now your entire shelter is a hot conductor).

VERY IMPORTANT - those cheap 3-led outlet testers don't always tell the truth, and the one case where they fail to catch a wiring mistake is one of the most dangerous. Over a decade ago, if the electrical system had no ground wire, it was unfortunate common practice to tie the ground pin of the receptacle to neutral AT THE OUTLET - if they also f-d up the wiring and swapped the hot/neutral (so tying the ground to hot instead of neutral) they just installed a landmine in a playground . The 3-LED type tester will indicate that there is only potential between the hot pin (which is incorrectly wired to neutral) and ground (which is incorrectly wired to hot), and the hot pin (which is incorrectly wired to neutral) and neutral (which is incorrectly wire to hot). Decode those two LEDs on the table and it shows: CORRECT!!

[Edit 3:] I firmly believe that pictures are worth more than words, and I am aware that many understand things better when shown them rather than told them, so here is an article that has a picture to go along with an explanation of this issue, and here is a youtube video showing how difficult this is to find if you're not aware of it:

[/Edit 3]

You really need to understand the electrical system to be able to troubleshoot it - this is why good electricians charge more if it's their first time to a site, they want to completely know what they're dealing with. Assume something is done right by someone else and your assumption will make you pay the price a eventually.

This goes for wiring you've done yourself by the way , hate to admit how may times I've caught my mistakes after a good night's rest and a fresh cup of coffee ("Who the F did this... oh - right.").