"Ground" is a different concept in AC and DC circuits.
DC circuits have a hot and a ground conductor while AC circuits have hot, neutral conductors and a ground wire. This is confusing to beginners because the return wire in a DC circuit is called a ground wire but in an AC circuit the return is the neutral. The ground wire in AC circuits is only a safety feature and will only carry current when there is a short in the circuit. The fact that DC grounds carry current and AC grounds don't explains why you can (and should) ground your AC panel to the body.
Without an AC ground to the bus body the body can become a 120 volt conductor if a loose AC hot wire were to come in contact with the steel body (search on "RV hot skin"). The ground wire enables the AC breaker to sense the short and trip the breaker. With no AC ground connection a short won't trip the breaker and anyone outside touching the bus could get a nasty shock if they were decently grounded.
Definitely ground your AC breaker panel to the bus body.
With respect, I think you are misunderstanding and misusing some of the terminology and concepts in a way that is adding to the confusion.
Specifically I think your understanding of the term DC 'ground wire' has led to erroneous conclusions about the DC grounding system.
Both AC and DC circuits have two
current carrying conductors. Generally referred to as
Hot and
Neutral in a single phase AC system and
Positive (+) and
Negative (-) in a DC system.
The terms are unimportant so long as you differentiate the concepts. It is incorrect to say that the return wire in a DC circuit is called the 'ground wire' unless the return path flows through a common ground (such as the vehicle chassis).
Both AC and DC systems can be grounded or ungrounded. It is nearly universal to ground AC systems, with DC, grounding is commonly employed but it is more situational. In both cases, the
grounding conductor is not normally a current carrying conductor.
The exception to this (and the source of your confusion I think) is situations like vehicle wiring or some integrated electronics where traditionally the grounding conductor and the negative conductor have been one and the same and both purposes are served by the same conductor. This is only the case in certain applications. It is important to understand that in these situations one conductor is filling both roles.
Confusing the terms confuses the concepts. The negative conductor in a vehicles electrical system came to be referred to as a ground wire because it
is a ground wire in that it bonds the negative side of the circuit to common ground. In a system that does not use chassis-return (or a common return path) it is inaccurate and misleading to refer to DC negative as ground. They are fundamentally different concepts.
Technically the terms are:
"grounded conductor" = AC Neutral or DC negative (in a negative ground system), these
current carrying conductors are bonded to ground and thus at the same potential / reference voltage as ground.
"grounding conductor" = The grounding system conductors (green, green-yellow, or bare copper) that bond the 'grounded' conductor to ground, or that connect the metal cases of components to ground or the grounding system ('equipment grounding conductors')
In practice is more common we use the terms Neutral or Negative wire for the grounded conductor and 'ground wire'
Further, a DC system does often need a safety grounding system for many of the same reasons an AC system does (safety, fault current path, etc). Discrete DC grounding systems are required and recommended in marine electrical systems, PV systems, RV house systems, etc. If you look at any reputable inverter designed for mobile systems
(for example), you will notice the DC side has three terminals Positive, Negative, and a grounding lug for an
equipment grounding conductor. And if you read the documentation you will see instructions are given for DC side grounding.
This is not the only component that is often grounded on the DC side, the National Electrical Code requires PV arrays to be grounded, battery banks are frequently bonded to ground with a dedicated grounding conductor and many manufacturers recommend or make provisions to ground solar charge controllers.
The long and short of it is whether AC or DC, the negative current return path and the path to ground are different concepts with different purposes, sometimes they overlap but frequently they don't using the term 'ground wire' confuses these concepts and is not applicable outside of the limited areas where ground and negative are the same thing. Skoolies and RV's straddle this line, on the vehicle side, ground=negative, but on the house side (AC and DC) ground and negative are not the same thing. If you look at any of house side components in your system or solar components you will see the terminals are marked + and - or positive and negative, and on at least a few of them you will see a separate connection for ground. Using the terms interchangeably leads to a lot of confusion, particularly for newbies but even for experienced DIYers. One thing that I agree with you about is the DC side can be different and more confusing than the AC side--one of the reasons I think proper terms are important.
I wish I could convey this in a more clear and concise manner, unfortunately that is not my strong suit. I have consulted the NEC code, the ABYC and USCG code, as well as documentation from a small handful of electrical component and wire manufacturers and am fairly sure none ever conflate or call the grounded current carrying conductor (negative or neutral) a 'ground wire' or anything similar. All of the resources I mentioned can be found
here
about misuse of the term 'ground wire' as it is so frequently misinterpreted and misunderstood, which greats a snowball of misunderstanding.
