Mobile/RV frame ground

[wesbrew]

Looking for advice regarding multiple voltages, AC, and DC chassis grounding on my 5th Wheel RV. Like most I guess, my RV factory 12 volt system is grounded to the RV chassis - the battery negative is connected to the RV chassis. I also have a 240v minisplit and a 4-1 PV combiner with surge arrestor...both which recommend grounding to the chassis. I also have the EG4 6000EX 240v inverter. The PV surge arrestor leaks some minimal DC current in normal operation as I understand by design - the case gives a little tingle shock. I am wondering what is the effect if the 12 volt DC negative is connected to the chassis and also the surge arrestor. For some reason this does not sound like a good idea to me. Next then, the minisplit is mounted to the chassis also so, as a side effect, the chassis DC negative current will be present on the minisplit case. Now then comes the AC green earth ground...but I have no ground rod in my off-grid RV. Should it also be connected to the chassis frame? Then also, assuming the inverter bonds ground and neutral when unplugged from shore power...there is always some unbalanced AC spilling over to the 120v neutral and thus the bonded earth ground. This all seems like a meltdown in the making to me. What is the safe approach to this problem?

 

[12VoltInstalls]

case gives a little tingle shock

I’m not sure that is actually ‘normal’
There is likely lethal voltage from the panels . You don’t want that leaking.
Something is not right.

I have no ground rod in my off-grid RV. Should it also be connected to the chassis frame

Yes

assuming the inverter bonds ground and neutral when unplugged from shore power...there is always some unbalanced AC spilling over to the 120v neutral and thus the bonded earth ground. This all seems like a meltdown in the making to me. What is the safe approach to this problem

there should be no current on the G/green/bare/ground EVER. Period.

It sounds like something (s) is seriously in need of troubleshooting.

 

[Checkthisout]

Looking for advice regarding multiple voltages, AC, and DC chassis grounding on my 5th Wheel RV. Like most I guess, my RV factory 12 volt system is grounded to the RV chassis - the battery negative is connected to the RV chassis. I also have a 240v minisplit and a 4-1 PV combiner with surge arrestor...both which recommend grounding to the chassis. I also have the EG4 6000EX 240v inverter. The PV surge arrestor leaks some minimal DC current in normal operation as I understand by design - the case gives a little tingle shock. I am wondering what is the effect if the 12 volt DC negative is connected to the chassis and also the surge arrestor. For some reason this does not sound like a good idea to me. Next then, the minisplit is mounted to the chassis also so, as a side effect, the chassis DC negative current will be present on the minisplit case. Now then comes the AC green earth ground...but I have no ground rod in my off-grid RV. Should it also be connected to the chassis frame? Then also, assuming the inverter bonds ground and neutral when unplugged from shore power...there is always some unbalanced AC spilling over to the 120v neutral and thus the bonded earth ground. This all seems like a meltdown in the making to me. What is the safe approach to this problem?

What?

 

[wesbrew]

I’m not sure that is actually ‘normal’
There is likely lethal voltage from the panels . You don’t want that leaking.
Something is not right.

Yes

there should be no current on the G/green/bare/ground EVER. Period.

It sounds like something (s) is seriously in need of troubleshooting.

I’m not sure that is actually ‘normal’
There is likely lethal voltage from the panels . You don’t want that leaking.
Something is not right.

Yes

there should be no current on the G/green/bare/ground EVER. Period.

It sounds like something (s) is seriously in need of troubleshooting.

the combiner box is the 4-1 from watts247 with surge arrestor. I talked Ian about the case giving me a shock. he said this is how lightning surge arrestors work, the case needs to be grounded to the Chassis. I agree the shock could be lethal with full sun power. but the RV 12 V loads, like LED lights slide outs and leveling jacks, are all rated for 12 V. If the combiner box is grounded to the chassis also and leaks voltage, it seems those 12 V devices would experience higher voltage than rated for. no? my panels produce 400v.

My point about connecting the green earth ground conductor to the chassis is this. If an appliance became faulty with a hot wire, touching its case, like a toaster, then that short circuit current would travel onto the chassis frame also. That would then put AC and DC on the Chassis at the same time.

do i understand this correctly? with 240 volt, there is 2 120 volt legs supplying different circuits. if the load is balanced exactly between those two hot legs then the white neutral leg is balanced to zero current. However, if the load is unbalanced between the 240 hot legs, then the white neutral will serve is the path for the current Delta. do i understand this correctly? then, if the green earth ground is bonded, with the white neutral that provides a path for current to the green earth ground. Then, if the green earth ground is connected to the chassis, the chassis wheel didn’t have AC current on it together with its 12 V DC current from the battery system.

 

[Checkthisout]

Why do you need a surge arrestor on your solar array?

 

[wesbrew]

Why do you need a surge arrestor on your solar array?

The surge arrestor is built in to the 4-1 watts247 combiner box I purchased...I assume only for lightning?

 

[Checkthisout]

The surge arrestor is built in to the 4-1 watts247 combiner box I purchased...I assume only for lightning?

Yeah but if lighting strikes your RV, I can assure you that the surge arrestor will not stop anything from getting cooked.

I would just get rid of it.

It's more likely to fail closed and shock you with panel voltage than it is to protect or the equipment from lighting.

In my opinion of course.

 

[12VoltInstalls]

seems those 12 V devices would experience higher voltage than rated for. no? my panels produce 400v.

The presence of voltage is not an indication of current.

Anyway, I’m getting lost in your description and can’t figure out what’s relevant

 

[mikefitz]

that short circuit current would travel onto the chassis frame also. That would then put AC and DC on the Chassis at the same time.

A correctly installed AC system would have overcurrent protection that would trip under the above conditions.
Without the PE connected to vehicle metal, any AC hot accidently connecting to the vehicle metal would cause an ongoing situation where this was undetected, until someone touches the vehicle metal and a metal bodied appliance at the same time.
To be really safe, the AC should have overcurrent and GFCI protection, and with vehicle metal bonded to AC PE. ( and a neutral to PE bond at the AC source.)

 

[12VoltInstalls]

GFCI protection

That’s the first thing I put behind the inverter when I started out with 200W of panels and a 1200W inverter. “Maybe there’s a problem in some system or fixture?” is what I thought, and until discovered I had a level of separation between me and the circuit to a casket.