Common AC and DC Ground?

[Fishyhead]

My camper has a shore power AC circuit and a PV circuit and battery. The DC circuit is completely independent of my truck's electrical system.

Currently, all camper DC circuits ground to a bus bar that's tied to the battery but I want to tie that bus bar to the camper's chassis. I believe the AC circuit is grounded to the chassis as well.

Can I use the same chassis ground for both DC and AC circuits? If yes then I plan on running a ground wire from the DC bus bar to the AC panel's ground bus.

 

[rando]

Electrically you can and should use the same ground and tie it to the chassis, that way any AC fault where a hot wire comes in contact with a metal part of the camper will trip the breaker/GFCI and not just energize your frame with 110V.

However, mechanically it may be better to use physically separate bus bars - one for the DC negative connections and a different one for the AC ground wires and then have those electrically bonded. This is just to keep it clear which system is which, you don't want to accidentally tie a DC wire into an AC circuit.

 

[Fishyhead]

Thank you. I'll ground the DC bus bar to the chassis near the battery.

Follow-up question - some of the DC devices like the inverter, AC-DC charger, and PV controller have a separate grounding lug. Should those lugs tie back to the same DC bus bar or to a separate one that then grounds to the chassis? It seems that if the current bus bar that the battery is tied to is also grounded to the chassis that it will be OK to ground those lugs there.

 

[rando]

Yes, you can tie those to the same bus bar.

 

[Vic Harder]

Tying all the DC loads to a bus bar is much preferred to having many grounds all over the camper. Ground wires can fail, and then you are using the framing of the camper to regularly carry current, which could lead to corrosion.

Also, knowing where all the grounds are makes troubleshooting a whole lot easier down the road.

Plus, it is visually more clear where the Shunt for your battery monitor needs to go.

Vic

 

[Jon R]

When you talk about the "ground" for your AC power I hope you mean the safety ground and not the neutral current carrying wire. I would not connect the AC shore power neutral to anything other than the neutral of the AC loads.

 

[ntsqd]

In a house the AC Neutral and the ground terminals are common at the breaker panel. Nowhere else, just there. It was a licensed electrician who pointed this out to me as he thought it ironically amusing.

 

[Jon R]

That he found it ironically amusing seems to indicate he doesn't understand there are good reasons to only tie the neutral to the safety ground at one location, which is a little scary given he's a licensed electrician.

 

[ntsqd]

He found it amusing because people make such a big deal out of keeping them separate when they're electrically common. If they're electrically common then they're electrically common and where that happens really is of no consequence. That you might not want it to happen more than once was a given, but that everyone gets so wound up about where it happens amused him.

I'm pretty sure that he fully understood the reasons behind it. It was the people getting wound around the axle about it that amused him.

 

[Machinebuilder]

I would find it amusing when he has a problem with a GFI receptacle blowing up because downstream there is a connection from neutral to ground.



I stumped me for quite a while. I found 1 stray strand hanging from the neutral contacting the grounded metal box.

so yes they are the same electrically, BUT a ground should never carry current.

I believe that current code requires a separate buss bar for ground and neutral, They are only bonded at the main breaker box, if there is a sub panel they are separate. I don't do household electrical work for other people so I don't keep up on codes.

 

[ntsqd]

That would fall under the more than one connection exception. He went from working on house wiring to industrial wiring to working as an electrician at a power plant where they think of 4180 VAC as "low voltage" (that still requires Arc Protective gear to make or break connections). I think he has a pretty solid grasp of what to do and what not to do.

When we had to re-wire code put in breakers like that of some sort. Sneezing near an outlet would trip them. Never mind trying to trying to run a vacuum cleaner from an outlet in the Hallway. That just wasn't going to happen, the breaker would trip every single time and in the process it shut off my WtW access. Sitting out in the storage container they no longer trip at all. I'm OK with new features that make something safer, but when those features interfere with or restrict the normal usage then I'm no longer OK with them and they're gone. The sensor that stops the table saw blade before it can draw blood is awesome, but the guard that would bind up and destroy the work piece on any cut more than a 45° must have gotten lost somewhere......

 

[Machinebuilder]

That would fall under the more than one connection exception. He went from working on house wiring to industrial wiring to working as an electrician at a power plant where they think of 4180 VAC as "low voltage" (that still requires Arc Protective gear to make or break connections). I think he has a pretty solid grasp of what to do and what not to do.

When we had to re-wire code put in breakers like that of some sort. Sneezing near an outlet would trip them. Never mind trying to trying to run a vacuum cleaner from an outlet in the Hallway. That just wasn't going to happen, the breaker would trip every single time and in the process it shut off my WtW access. Sitting out in the storage container they no longer trip at all. I'm OK with new features that make something safer, but when those features interfere with or restrict the normal usage then I'm no longer OK with them and they're gone. The sensor that stops the table saw blade before it can draw blood is awesome, but the guard that would bind up and destroy the work piece on any cut more than a 45° must have gotten lost somewhere......

I work on industrial machines as my vocation.
I am sure he is very good at his job, I'm glad I don't deal with more than 460V systems.

Industrial electricians and residential electricians are very different.
Industrial machine electricians are very different than both.

I believe you are referring to Arc Fault interrupters, I wouldn't think about using them in my house.
I also do the work myself and don't need permits and inspections.

I sometimes wish I had the saw stop table saw, but my 60? year old powermatic with no safety anything works really well and it is a vary occasional use.