Confused about grounding terminal connection in RV

[chilly]

I have a Morningstar TS-MPPT-45 charge controller I'm installing in an RV.

There is a grounding terminal in the controller chassis. I guess in a house or something you would connect this to an earth ground (?) - as it's grounding the device itself in case of a short or something (?)

They say "Do not connect the system negative conductor to this terminal". But in my system, system negative is a wire running to the frame, then to the battery negative. Obviously I don't have a true earth ground rod in an RV. What else can I do with this terminal? All I can think is that they mean not to connect the system negative conductor ***ONLY*** to that terminal. That of course wouldn't work. But in my case, does it make sense to connect the system negative wire to both connectors - serving both as the charging circuit and the chassis ground?

I can't fathom any other options.... seems ridiculous to run another parallel wire from the box to the same point on the frame as the battery line is already going.

[inetdog]

I have a Morningstar TS-MPPT-45 charge controller I'm installing in an RV.

There is a grounding terminal in the controller chassis. I guess in a house or something you would connect this to an earth ground (?) - as it's grounding the device itself in case of a short or something (?)

They say "Do not connect the system negative conductor to this terminal". But in my system, system negative is a wire running to the frame, then to the battery negative. Obviously I don't have a true earth ground rod in an RV. What else can I do with this terminal? All I can think is that they mean not to connect the system negative conductor ***ONLY*** to that terminal. That of course wouldn't work. But in my case, does it make sense to connect the system negative wire to both connectors - serving both as the charging circuit and the chassis ground?

I can't fathom any other options.... seems ridiculous to run another parallel wire from the box to the same point on the frame as the battery line is already going.

If current if flowing in the negative system conductor (which it is most of the time) then that terminal will not be at exactly the same voltage as the earth/ground terminal with a non-current-carrying wire. This assumes that the CC does not just connect the two together internally but handles them separately. (I.e. the CC is not a hard negative ground system).

[Sunking]

Circuit conductors carry normal load currents. Bonding (formerly ground) are forbidden to carry any normal load current. Ground conductors only carry current in a fault condition.

There are really only two good reasons to ground a system or ground an equipment chassis.

1. Provide a planned fault path for current to return to source with a low enough impedance to operate a current over protection device.
2. Minimize touch potential differences under normal operating conditions.

But to answer your question is to define what GROUND MEANS. Well it basically means nothing, but by definition: Ground is Earth or a Body in place of earth. So with an RV ground is the vehicle chassis.

[chilly]

@intedog - the 'ground' and the negative terminals are indeed separate (although the negatives for the battery and the panels are common)

@sunking - I'm not sure what you mean by "2. Minimize touch potential differences under normal operating conditions."

Note that my negative lead is a 4awg 10' run to the frame, then to the battery, which should be fine for any type of fault my 45A the system could conceivably see (100A should be fine over that run). And I don't plan on using any ground fault systems.

So I'm still not sure what I should do with this lug. Maybe I should call Morningstar Monday. I see a lot of pics of DIY installs not using it (RV). I also read of some guy who says he accidentally touched the hot remote signal line to the chassis and fried the controller. Would it be a bad idea to just jump this to the negative wire, rather than run yet another fat wire all the way to exact same grounding point (that kills me!).

[Sunking]

Touch potential means voltage.

You have two options for the Ground Terminal. Sense this is a 12 volt system forget it. Of like I said Ground in a vehicle = Frame and Chassis.

[Svg09851]

Help with grounding please :

Main question is would you ground the inverter chassis to the rv chassis given there is a grounding terminal provided on the inverter chassis which looks like it would accommodate about 16 awg wire (is that big enough?) also would you ground the 12v battery bank to the rv chassis directly from the negative terminal of the bank? Or is it better to have a floating system (no grounding at all) (hope terminology is correct)

[Mike90250]

Floating battery ground requires each battery terminal be fused

Grounding the inverter. Only if it's a pure sine inverter and is Mobile Rated, and the manual calls for it to be grounded. In a fiberglass RV, 3rd wire ground may not always prevent shocks. Small inverters cannot reliably trip household circuit breakers.
Usually, mobile inverters have GFIC outlets to protect the user. But when all else fails, read the inverter manual