"grounding" question

[SpitballJedi]

I'm just trying to verify if I need to "ground" my 12vdc system. i.e. do I need to bond the (-) of any part of it to the truck frame or chassis?

All of my loads have 2 wires and both wires will be ran to a fusebox connected to the battery. I see nothing to indicate any of it needs to be bonded to the frame/body/chassis for "grounding".

I have 200ah lifepo4 battery for my truck bed camper. For now, I won't be installing an inverter, solar, or dc-dc charger. The system is not connected to the trucks battery or alternator in any kind of way. All my loads are 12vdc. The only AC component is an AC charger and it will only be used while all the 12v stuff is disconnected. I have a shutoff switch to shutoff the dc system when I use the AC charger and I remove the AC charger before I turn the switch back on.

Please correct me if I'm wrong, but given my particular system, do I need to bond anything to the frame/body/chassis?

[flboy]

As long as the 12vdc circuits have a direct return to the battery, there is no need. In automobiles in particular, the battery negative to the chassis (called ground sometimes) is just a return and reduces the need for all direct wires to be run to the battery terminal. Basically, the chassis is being used as a negative bus bar to complete the circuit in this case. It is less expensive and saves alot of wiring.

Bottom line, as you have described it, no need to connect negative of 12vdc battery sysyem for truck camper to the truck chassis. Running direct returns to the battery is okay.

Sent from my SM-N970U using Tapatalk

[Sparksalot]

I kept the cabin system totally separate from the chassis system for a decade. It worked fine. I only bonded the two together when I rewired the connection to the TV as a 7 wire cable to assist in charging the battery.

[John61CT]

Yes, both the engine DC circuits and House bank should share a common "chassis ground"

This of course is not true earth ground, just a shared common reference potential.

Any important or high current DC loads should have a Negative Return wire path back to source, not relying on the chassis.

None if this has anything to do with AC. IMO the charger should be the only item plugged into shore power, all AC devices run off the House bank via inverters.

Anything more complicated hire a pro sparkie, marina guys usually more au fait than the RV ones.

[SpitballJedi]

Thanks for the responses and confirmation of what I already suspected.

Yes, both the engine DC circuits and House bank should share a common "chassis ground"

This of course is not true earth ground, just a shared common reference potential.

Any important or high current DC loads should have a Negative Return wire path back to source, not relying on the chassis.

None if this has anything to do with AC. IMO the charger should be the only item plugged into shore power, all AC devices run off the House bank via inverters.

Anything more complicated hire a pro sparkie, marina guys usually more au fait than the RV ones.

I'm not using an inverter and my house DC circuit is completely separate from my engine DC circuit and I have no AC loads on my house circuit. In my case, why do I need the engine and house circuits to share a common "chassis ground"?

[John61CT]

A purely "floating" House system is super unusual, and even if perfectly safe today may cause problems as changes are made in future.

Really in departing from mainstream conventions, I would rather ask "what reason do you have not to"?

The only cost is a length of robust wire properly terminated both ends.

Separate topic, why would you not want to be able to charge / jump your Starter from House inputs when needed?

Or take advantage of alternator charging House while driving?

Not much complexity involved, just a bit of learning.

[Capebuild]

I had asked the same question a while back. You may find it helpful to revisit that thread.
viewtopic.php?f=30&t=74051#p1281706

FWIW, I did not ground to the chassis.

John

[bdosborn]

The AC battery charger case is required by the NEC to be grounded to the vehicle frame.

NEC 551.4
(B) Voltage Converters (120-Volt Alternating Current to LowVoltage Direct Current). The 120-volt ac side of the voltage converter shall be wired in full conformity with the requirements of Parts I, II, and IV of this article for 120-volt electrical systems.

(C) Bonding Voltage Converter Enclosures. The non–current carrying metal enclosure of the voltage converter shall be connected to the frame of the vehicle with a minimum 8 AWG copper conductor. The voltage converter shall be provided with a separate chassis bonding conductor that shall not be used as a current-carrying conductor.

It provides a current return path for the AC circuit breaker supplying the charger that will open the breaker if there is a hot wire to frame fault. This prevents you from being the current return path if somehow the hot wire of the charger touches the frame and then you touch it. Now, the probability of this happening is pretty low but people have been know to drive a screw into a hot wire accidentally. That's why the metal skin of a camper is required to be bonded to the frame too. I used a #12 to the frame in my camper since its a 20A shore connector and not a 50A.

Bruce

[SpitballJedi]

A purely "floating" House system is super unusual, and even if perfectly safe today may cause problems as changes are made in future.

As unusual as it may be, I believe it's what I will have. I can always address any changes I may make as I make them.

Really in departing from mainstream conventions, I would rather ask "what reason do you have not to"?

The only cost is a length of robust wire properly terminated both ends.

I don't believe in doing unnecessary work or adding unnecessary components and parts. I can do it when and if becomes necessary.

Separate topic, why would you not want to be able to charge / jump your Starter from House inputs when needed?

Or take advantage of alternator charging House while driving?

It's not that I don't want to do those things, it's that I don't need to do those things. Adding those capabilities means buying different new equipment and doing more work to accomplish something I have no need for. If my 200Ah lifepo4 is fully charged before I leave home, it's way more than I need for the 1 or 2 nights I would be using it. Way more. As for jumpstarting, I already have a jumpstarter pack. But, this is getting off topic. The topic is about my system as I have it planned.

This is my AC charger https://www.amazon.com/gp/product/B08C2JN76Q/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1.

[SpitballJedi]

The AC battery charger case is required by the NEC to be grounded to the vehicle frame.

NEC 551.4
(B) Voltage Converters (120-Volt Alternating Current to LowVoltage Direct Current). The 120-volt ac side of the voltage converter shall be wired in full conformity with the requirements of Parts I, II, and IV of this article for 120-volt electrical systems.

(C) Bonding Voltage Converter Enclosures. The non–current carrying metal enclosure of the voltage converter shall be connected to the frame of the vehicle with a minimum 8 AWG copper conductor. The voltage converter shall be provided with a separate chassis bonding conductor that shall not be used as a current-carrying conductor.

It provides a current return path for the AC circuit breaker supplying the charger that will open the breaker if there is a hot wire to frame fault. This prevents you from being the current return path if somehow the hot wire of the charger touches the frame and then you touch it. Now, the probability of this happening is pretty low but people have been know to drive a screw into a hot wire accidentally. That's why the metal skin of a camper is required to be bonded to the frame too. I used a #12 to the frame in my camper since its a 20A shore connector and not a 50A.

Bruce

This is my AC charger https://www.amazon.com/gp/product/B08C2JN76Q/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1. It's not the kind you may be thinking of. I don't see a way to do what is described above. I really only plan to use it at home to make sure my 200Ah lifepo4 is topped off. I will carry it in the truck just in case though.

[SpitballJedi]

I had asked the same question a while back. You may find it helpful to revisit that thread.
viewtopic.php?f=30&t=74051#p1281706

FWIW, I did not ground to the chassis.

John

I'm likely not going to either unless I get a compelling reason to do otherwise.

[Tom&Shelly]

I'm late to the party but also didn't ground our DC system to the chassis. Works great!

We've never had trouble with our wiring, but, in my opinion, if we did, having dedicated wired returns would make trouble shooting easier.

As Bruce mentions, if you have a shore power connection, the chassis needs to be tied to the AC ground for safety (and to meet code). but with the charger you're showing, it's not a problem.

Tom

[SpitballJedi]

I'm late to the party but also didn't ground our DC system to the chassis. Works great!

We've never had trouble with our wiring, but, in my opinion, if we did, having dedicated wired returns would make trouble shooting easier.

As Bruce mentions, if you have a shore power connection, the chassis needs to be tied to the AC ground for safety (and to meet code). but with the charger you're showing, it's not a problem.

Tom

Thank you. That's the sentiment I seem to be getting on another forum as well.

[dmdc411]

bdosborn, you brought up something I never thought of. The exterior aluminum skin needs to be grounded to the chassis ground. Especiallyif the aluminum skin is attachedto a wood structure like most of us use. It never occurred to me. I'm not a "licensed electrician", I'm a "registered unlicensed electrician". Just another way for the state to take mo money, and track my work under my employers master electrician. Without the skin grounded to the chassis ground, an ac power short to the skin would be bad. As in, if your shore power, that passes through the skin if you use an rv shore power plug, some how was to be damaged, the skin could be hot!

Sent from my SM-G970U using Tapatalk

[SpitballJedi]

bdosborn, you brought up something I never thought of. The exterior aluminum skin needs to be grounded to the chassis ground. Especiallyif the aluminum skin is attachedto a wood structure like most of us use. It never occurred to me. I'm not a "licensed electrician", I'm a "registered unlicensed electrician". Just another way for the state to take mo money, and track my work under my employers master electrician. Without the skin grounded to the chassis ground, an ac power short to the skin would be bad. As in, if your shore power, that passes through the skin if you use an rv shore power plug, some how was to be damaged, the skin could be hot!

Sent from my SM-G970U using Tapatalk

Fortunately, I won't have an aluminum skin and there won't be any wires running through the walls of the truck or shell. Eventually, If I add solar, I'll have to run wires through the skin of the shell, but it's wood, XPS, and PMF. I'll worry about all that if I every decide to do it.