Flexmax 60 grounding

waynec5

My RV's chassis is grounded to the grid power, I've mounted the flexmax 60 directly to the rv wall which means it's also grounded to the grid, is that okay? 

BB.

That should be fine... I am guessing your RV wall is metal and not wood like many in the USA are (you are in South Africa?).

Many times with vehicles, the metal to metal bonding is not very good (frame rails to rubber vibration mounts to chassis sheet metal, motor thru rubber mounts to frame/chassis, doors on hinges with poor conduction, etc.). So, many times, if you have something you want "grounded"--You may have to jumper frame to chassis with heavy wire/braided wire, etc. (frequently done with HAM radio in vehicles to lessen the chances of random pops and static).

The other grounding issue to discuss is the battery bank. Mostly, we negative ground the battery to the metal chassis/frame (same issues with above need to carry grounds through to various "pieces" of the vehicle).

Then back to a fundamental question... To major reasons to ground "things". One is to prevent electrocution. You don't want a (for example) metal sink (or metal chassis of solar controller) to get crossed with a "hot lead" and electrocute somebody washing dishes/touching a metal stove, ete. Another example would be a metal RV on rubber tires--Gets crossed with 120/240 VAC hot lead and no grounding. Person grabs the metal door handle after a rain (puddles, wet grass) and gets electrocuted. The "Ground Connections" back the shore power source needs to be heavy/good enough to short circuit the hot connection and trip the shore power/RV circuit breakers. 

This can be addressed with a GFI / RCD device at the shore power (or on RV sockets). The GFI / RCD measures the current through the AC hot wires and if the Hot/Return current is not equal (i.e., some current is going to green wire safety ground), then the GFI / RCD faults and disconnects the AC loads (GFI=Ground Fault Interrupter--North America; RCD Residual Current Device for much of rest of world).

https://en.wikipedia.org/wiki/Residual-current_device

In North America, GFI protection is required for an AC outlets near water (sinks, outside, etc.).

Another major reason for grounding is lightning. You want the lightning current to flow "outside" of the living area and directly to earth. If this is a permanent installation (trailer park), and you have lightning issues--You may want to review how to address that issue (such as a ground rod/plate buried in the earth then connected to your main power panel with (relatively) heavy wire/cable, using surge protectors, etc.).

With RVs that have alternate power sources (shore power, AC inverter, genset, etc.)... In North America, we connect the Neutral+Grounds together in one location (typically the main power panel) for safety. Gets complicated when Shore Power has N+G bond, Genset may have N+G bond, AC inverter may have N+G bond--Or they may not). Multiple N+G bonds are not standard and can cause issues. No N+G bonds can cause issues with protection against electrocution/short circuits).

-Bill