Expanding AC distribution panel

Andonso wrote:

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The only difference is when I previously tested the one of the green wires and found continuity to ground the other green wire wasn't connected to 12 volts to supply power to the frigs pcb.

So either my first test wasn't correct or providing power to the first green wire connected to the frigs pcb effected the second green wire.

I really need to go over and test everything and double check my initial findings, which performed quite quickly.

However the fused wires are currently too short to connect the PD dist panel, so I want to first lengthen them before continuing my tests and find where the other wires go to.

I'm going to take a look at my neighbors fuse panel to determine what size fuses his RV is using.

Continuity is fairly simple it just means there is an electrical path or connection between two points in a circuit.

Most DMMs have a continuity tester built in where all you need to do is touch the probes on two different points in a circuit and if the two point are connected then the DMM will beep.

Continuity testers are used to test for DC ground continuity to determine if a wire has a ground short (path to ground).

While testing for continuity from AC to DC I found the AC neutral to have continuity to DC neg- which is also chassis ground. I guess that's one thing AC and DC have in common is chassis ground

Since AC continually reverses polarity, if the AC is active you should find some very quick beeping when putting a continuity tester between AC neutral and DC neg- ground.

So AC uses a closed loop sometimes referred to as a ground loop. This is where things become a bit more complicated as AC actually has an alternating current path to ground that potentially causes interference in electronics. There are NEC codes that state how many grounding rods a pud service requires. At one time services used for RV had an additional grounding rod however NEC changed that so now homes also need to be better grounded with additional grounding rod or rods that need to be spaced so many feet apart, etc.

Poor grounding can sometimes lead to problems with electronics such as e.g. a stereo receiver that produces a humming sound or static noise. What is sometimes helps is installation of a ground loop isolator on the audio inputs. However ground loop isolators don't always work.

One potential reason you may get different readings of continuity with a multimeter is that you checked with the leads reversed one time and the circuit has a semiconductor of some sort (a diode or transistor) that only conducts in one direction.

I think you're a little bit confused on the AC stuff. There should not be a connection between the AC neutral and chassis ground on the RV with the shore power cord disconnected; they are supposed to be entirely separate on an RV. If you do have a connection, that's a ground fault and should be fixed. When plugged in, you will see continuity there because the AC neutral and ground are bonded together at the main service panel.

AC neutral is a current carrying conductor, of course, but it's at ground potential, so you won't have (significant) voltage present getting from the AC service to the DC system due to that. Even if you did, it wouldn't affect the DC system particularly because the +12V would just be offset from the varying chassis ground voltage; the entire DC system would float at varying voltages, but the voltage applied to the loads would remain constant.

None of this has is affected by whether the system is properly earthed or not, though that is an important safety consideration for other reasons. (Of course, in a system with bad or missing earthing, the neutral and chassis ground could be floating to some arbitrary voltage relative to earth, but the relationships between them and between the chassis ground and 12V system voltages would not be affected.)

Audio ground loops are a rather different topic, and not particularly related to what you're looking at. A normal AC circuit generally won't have a ground loop, though I don't think that would be strictly prohibited by the electric codes. I may be wrong about the code requirements.