Expanding AC distribution panel

I believe I said green for the frig. When I removed the 6300 I remember two green wires on the same fuse.

After removing the 6300 I tested all the wires that were connected to fuses for ground continuity i.e. to determine if any of fuse wires were somehow had a path to ground and found two or three wires that beeped when I touched one DMM problem to the wire and the other to the #8 neg- or ground wire.

One of the green wires produced a beep and the other green wire I found had continuity to the frigs pcb 12 volt wire that connects to the PCB to supply power.

I now have the one green frigs wire that supplies 12V to the frigs PCB connected to my Xantrex charger along with several other fused wires such as lighting and other found to be connected to the some of the controls of the range hood such as for water level, hot water heater, etc.

However I just went over and tested the other green wire that was on the same fuse as the other green wire and now it has no continuity to ground.

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.

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.

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.

Thanks for the explanation. I thought continuity was not related to pos-neg, just that it was not "open". Anyway, you can have more than one negative connection and more than one positive connection using parallel pos or negs. Maybe that is the situation with your mystery wires. Of course two pos would make a pos fuse on one useless.

Perhaps this is the time to have the power on to check actual on or off instead of no power continuity? You just want to get things to work or not.

If all the negs are too short, you can use the original neg buss and run a single fatter wire to the new neg buss. If the positives are too short, you have to extend them to their individual fuses.

(I had the furnace and fridge mixed up. Well, they both start with f)

I know RV inverters have a "chassis ground" (to the RV frame) on the outside of their metal casings to reduce radio interference. I ASSume the chassis ground on a deck mount converter is for the same reason, don't know.

DrewE wrote:

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.

I didn't say AC neutral and chassis ground have a full continuity connection "with shore power disconnected". While checking continuity ("with shore power connected") using a DMM the DMM started to beep very rapidly with one probe connected to AC neutral and the other prob connected to DC neg- chassis ground. (same rapid beep with probes in either direction.

One explanation is the DMM (set to ohms/beep) is detecting differences in potential (VOLTAGE) between a current-carrying conductor (NEUTRAL) and a non-current-carrying conductor (GROUND).

I think the only reason I mentioned it is because I added it to my continuity tests of the entire system, (with shore power connected and disconnected) which included disconnection / connection of 12VDC from the batteries. Chassis ground is one commonality between AC and DC however which are essentially separate electrical system types until you convert AC into DC.

It's been a while since i've installed PUD service panels and re-wired an entire RV (removed old alum. 2 wire upgrading the entire RV to copper three wire with hot-neutral-ground.

But I remember grounding using NEC codes which at the time there were differences grounding a RV vs a house. I think NEC has since changed some it's grounding codes for homes.

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DC systems existed prior to AC which has primarily replaced DC due to AC being able to travel cost effectively over longer distances, not requiring larger cabling.

I do remember reading about certain types of high voltage carrying systems DC is preferred over AC. IIRC some types of extremely high voltage system DC is sometimes preferred.

There are very high voltage current carrying systems that are DC. Various factors are involved such as cost, some systems it's more cost effect to use AC while others DC. But I'm not really up on all the details, I would need to find and re-read the article(s) again.

Anyway I'm currently am trying to figure out what size fuses to use and which wires should be together on the same fuse. I have an idea of which size fuse to use but I think I'm going to take a look at my neighbors RV to see what size fuses their RV is using.

Well I found all my dc lighting and bathroom fan plus some other equipment that uses DC.

The only 12 volts DC I actually use is the rv lighting and the frig. The only other 12 volts I've used while full timing is the 12 volt cig. lighter outlet once in a while.

My micro is on a separate circuit. My water heater isn't originally gas/electric, has 400 watt (AC) rod that installed that plugs into an AC outlet. It's thermostatically controlled and only on if the water drops below a certain temperature.