My RV setup: MPII 48/3000/120 with AC/DC distribution panel, and a 100AH battery (48V of course). 30 amp. I’ve done hours of internet research and am still unsure how to proceed.
Question 1: There is lots of conflicting info online about correct protocol for grounding MPII system to vehicle chassis. I initially planned to have one positive and one negative busbar for the whole system, with the negative busbar connected to vehicle chassis, but am now not sure about that. Am I supposed to have two separate chassis ground wires, one each for DC and AC which meet at a common point on the chassis, or is it OK to ground everything via the negative busbar to the chassis?
Question 1A: My internal cabling is 2awg copper, but my current vehicle chassis ground is 4awg aluminum clad (I only had the 4awg on hand when I was laying out wires and I had read that one size smaller was OK for chassis ground. I can’t change that run now, but can of course add a new one). Also, the internal cabling runs are short, but the ground wire is about 10 feet. Would that ground be sufficient to ground everything, or sufficient for either AC or DC individual grounding if it turns out I need two separate vehicle chassis grounds?
Question 2: What am I to do with the shore ground input wire and my AC1 output ground wire? I’ve seen people say that one or both should be connected to a vehicle chassis busbar, and I’ve seen people say that one or both should be connected to the ground bus on the AC distribution panel.
Question 3: Do I ground the MPII case to the vehicle chassis or to the distribution panel AC ground bus?
Question 4: I currently have a 250A/58V fuse between battery & MP, individual DC fuses in the distribution panel, and AC breakers. Is that all the fuses I need, or am I missing something?
Thanks in advance for any help. I really did a lot of research but can’t find definitive answers….and I want to make sure I do it right the first time bc I’m full time in this RV.
yes, its fine to do this. Just make sure the ground connection is well executed, and capable of carrying the DC current. Also use an rcb for the Ac loads.
Aluminium cables can only carry a smaller current than copper. you say this is aluminium clad? what is the base metal?
You probably need to add a second ground wire. In mobile situations, all cables should be fine stranded copper, preferably tinned.
You should also be using an isolating transformer, or you will have problems with input ground leakage devices tripping. The incomming ground terminates in the isolating transformer, the case of which is connected to your local ground bar.
whichever is more convenient. All AC grounds on the MP2 are internally connected to the case.
See RCB above - residual current breaker, GFI or similar device.
I disagree with this, but i guess thats where the root of the uncertainty is, both sides/opinions have their arguments and pros/cons.
Grounding connections are a safety component, that under normal circumstances do not carry any current, but a negative busbar is an active component that usually carries current. A negative busbar should only have a single connection to ground. If you want to distribute multiple grounds to other things, use a dedicated ground busbar rather than connecting everything to the same negative busbar.
Theres lots of RVs out there that use the ACin directly, without issue. However, you are then relying on the AC source for it to be properly grounded (and also its neutral to be grounded somewhere) which is not always certain on some camp sites. An RCD on the input side can mitigate some risk, but yes, an isolation transformer and your own grounding rod would be ideal (but very uncommon in RVs, at least to me)