mcubberley wrote:They are not tied together. The items you pointed out supply the AC power to the converter unit (think of the converter as an appliance that needs an outlet) as well those are two separate bus bars so the greens and whites would not be intermingled. This is what sends ac power to the battery tender/charger so the AC neutral, hot, and ground never interacting in a way that would suggest they are common to anything on the DC side.
When I did my install I screwed up and tried to use the green bus bar in that picture to serve as the negative (black) side of my DC circuits. This lead to a current leak on my AC ground which was not a good thing. One needs to connect the DC black (-) directly to the battery or at the point where the battery black (-) connects to the unit with heavy gauge wire. This closes the DC circuits. Again referring back to my blunder connecting them to the AC ground bus bar or the negative bus bar did not work and caused the current leak across my AC ground.
So the AC neutral(white), AC ground (green), and the DC - (black) should all be treated as separate and different things because they are different and should not be treated as a bunch of negatives, grounds or neutrals.
This is all just based on my experience and also with scouring the various posts I researched on this site.
Like I said I don't have this converter, so I'm just going by drawings and the owners manual on the internet.
I agree, AC-Neutral, AC-Ground, and DC(-) are all different things and the differences should be respected.
Since, as you point out, in this converter they are not tied together, that leads me to conclusion that *at the converter* the DC(-) is floating.
So lets take a look at all the potential (no pun intended) "grounds" in this system:
1. TOW VEHICLE CHASSIS GROUND -- The tow vehicle will have its BATT(-) tied to the frame/engine block/body. The charging system (alternator) will be grounded to the engine block. The towing harness will have a ground wire attached to the body or chassis providing a return path back to TV-BATT.
2. SHORE POWER EARTH GROUND -- To get a complete picture, we have to go back to the service drop at the "telephone pole". The top wire on a telephone pole is a ground wire. If you pay attention, every few poles there is a cable running down to the ground. This puts the ground potential at the highest elevation for lightning protection of the distribution lines. But this ground doesn't run to your house/building.
2a) On the pole (let's assume a simple residential case) there is a split-phase transformer that steps the voltage down to two 120VAC phases, 180 degrees apart, for 240VAC between the phases, and a neutral. The output of this transformer is floating (i.e. no ground reference) and three wires are run to the main AC panel of the building. The two "HOTS" (L1 and L2) are connected to two terminals of a ganged circuit breaker (assume 100A each). The output of the circuit breakers are attached to the two hot buses, to which other breakers can be installed. The NEUTRAL from the transformer runs into the panel and is connected to the neutral bus bar in the panel. Right now the AC system in the house is floating, i.e. no reference, and very unsafe, so a long metal rod is driven into the ground right outise the building where the AC panel is and a fat cable is connected to it. This EARTH GROUND cable is run into the AC panel and it is tied to the AC-Neutral (aka BONDED or BONDING). Sometimes there are separate neutral and earth ground buses, but they are bonded together here for safety (this prevents the AC-Neutral from "floating" and creating a shock hazard.
2b) From the AC panel three wires (L, N, G) at 120VAC are run to the pole (shore power pole) in the campsite. Usually these wires are buried using cable rated for "direct burial". It can be a long way (a couple hundred feet) from the AC panel to the pole, so this is why I would always use GFCI breakers or outlets in a trailer. This is a measure of protection, cuz ground over there won't be quite the same as ground over here.
3. TRAILER CHASSIS GROUND -- chances are all the tail lights and possible the running lights of the trailer don't have a DC return wire (or maybe a really short one) and they depend on the chassis (frame) of the trailer for current to get back to the wire harness and back to the TV-BATT(-). If the trailer lights aren't attached to the chassis (as is the case in many teardrops), then the builder will need to run return wires back to the "ground" connection of the wire harness.
3a) Many RV/auto appliances will use TRAILER CHASSIS GROUND for their return path.
3b) It appears from the wiring diagram that the PD 4045 (no DC return bus), that they are relying on the builder to us TRAILER CHASSIS for the return path.
3c) To accomplish this the, TRAILER BATT(-) is terminal connected to the TRAILER CHASSIS GROUND.
3d) RV manufacturers, because of all the non-conducting goo they put on seams, they BOND the metal framework/skin to the TRAILER CHASSIS GROUND also, so that lights and stuff have a return path.
3e) When the wire harness is connected (and to an extent, when the trailer is on the hitch), the TV and the trailer will have the save reference potential and TV CHASSIS GROUND = TRAILER CHASSIS GROUND.
4. CONVERTER GROUND -- The AC wiring coming into the trailer will connect the EARTH GROUND of the AC mains to the converter at the ground bus. I wouldn't say it's "floating", but it is a long way back to the stake in the earth.
4a) The PD 4045 drawing shows that there is a L, N, and G wore going to the converter/charger. L and N go to a transformer and I will assume this is completely "isolated" (there is no common terminal for AC-N and DC NEG on the transformer), so the battery output (and the battery) will be "floating" (i.e. it has no ground reference) unless the BATT(-) is tied to something. That something should be the trailer chassis.
4b) The EARTH GROUND wire going from the ground bus to the converter/charger circuit is probably tied to a metal box (cage) that encloses the charger circuitry. This protects you in case of an insulation fault/short within the charger (the circuit breaker will open).
5. For safety I would personally also EARTH GROUND the trailer chassis to the the EARTH GROUND. This will protect you (the breaker will open) in the event of a AC insulation failure.
You say you had a current leak? I wonder where it was coming from and where it was going? Nothing in the foregoing would, in an of itself, cause a current leak.