Inverter Install

[CRoots]

I don't need an adapter, it's a regular three prong for shore power, so I did use a regular extension cord from inverter to shore power plug and got the same ground fault.

It seems like if I apply the power at or before the junction box (from perspective of shore power) I get a ground fault, but if I apply power passed the junction box everything is good. Hmmm...seems the junction box is an issue... I have not tried to power the system the way it was designed (shore power, no inverter), but maybe I should and see if it works...

Another idea I had is to use the suicide cord and connect to the back of an outlet, essentially the same as doing the male to male, but with hard connections instead of a plug. That would take the junction box out of the picture.


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[madmax718]

do a continuity test on the ground from the shore power line to one of the battery posts. Someone may have just used the body as a common ground plane.

 

[verdesardog]

The truck chassis should be earth ground on your shore pwr cable so that when plugged into real shore power the chassis IS grounded to a real earth ground. If you are having problems pluging your shore pwr into your inverter and getting gfi faults but it works with real shore pwr then it's an issue with your inverter. Maybe the gfi doesn't like the 12v ground and "supposedly" earth ground together. Make sure the wiring in the vehicle 110v does not have neurtal and ground connected together somewhere.

If you don't know what you are doing get a professional to do the job right so no one gets electocuted!

 

[G35Vortec454]

I don't need an adapter, it's a regular three prong for shore power, so I did use a regular extension cord from inverter to shore power plug and got the same ground fault.

It seems like if I apply the power at or before the junction box (from perspective of shore power) I get a ground fault, but if I apply power passed the junction box everything is good. Hmmm...seems the junction box is an issue... I have not tried to power the system the way it was designed (shore power, no inverter), but maybe I should and see if it works...

Another idea I had is to use the suicide cord and connect to the back of an outlet, essentially the same as doing the male to male, but with hard connections instead of a plug. That would take the junction box out of the picture.


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OK, so the problem is a ground fault. But before tackling that, it looks like your shorepower cable is also homemade, not a built-in RVIA shorepower cable installed in the original motorhome/RV. As far as I know class B rv/motorhomes came with 30A shorepower service cables.

Anyway, are you getting a ground fault as reported by your inverter, and it shuts of?
Or are you getting a ground fault when you connect an appliance to a GFI outlet in the RV, and it trips?

Which one?

 

[CRoots]

Negative on the homemade shore power. Keep in mind this vehicle is model year 1972. All wiring is very integrated into the vehicle.

When I was getting the fault (inverter connected in junction box or farther up stream), it was an immediate fault and the inverter had no load (nothing plugged in). The fault happened just a split second after turning on the inverter.


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[G35Vortec454]

Negative on the homemade shore power. Keep in mind this vehicle is model year 1972. All wiring is very integrated into the vehicle.

When I was getting the fault (inverter connected in junction box or farther up stream), it was an immediate fault and the inverter had no load (nothing plugged in). The fault happened just a split second after turning on the inverter.


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So are you saying the inverter IS the ONE tripping on ground fault? If so, check and follow all installation instructions for you Samlex inverter. Then I suggest the following steps:

1. Unplug the shorepower cable from the inverter.
2. Turn on the inverter. If ok, proceed.
3. Turn off or remove all the fuses in the distribution box/panel, which I hope has one for your 1972 rv, if not, stop and it's time to install one.
4. Plug the shorepower cable to the inverter. If ok, proceed; otherwise the problem is in tha section of the ckt. Fix it before proceeding.
5. Turn off inverter and put one fuse, turn on inverter. If ok, proceed.
6. Repeat #5, installing one fuse at a time, until the inverter faults.

Also, if there is a GFI receptacle in the motorhome, check it to make sure it's not shirted or leaking. If it's 30 years old, throw it away, replace it.

I hope this will help you isolate the problem ckt.

 

[G35Vortec454]

do a continuity test on the ground from the shore power line to one of the battery posts. Someone may have just used the body as a common ground plane.

RVs could either have a floating neutral or the neutral bonded to ground.

OP, check your Samlex inverter if it requires a floating neutral or the other.

 

[CRoots]

The fault is given by the inverter (little red light comes on), but caused by something external to the inverter.

As I said earlier, inverter works fine until the shore power cable is plugged in, then it registers the fault and kills the voltage. Same thing when suicide plug is used in the junction box (distribution box). There is only one circuit breaker in the box (there is only 4 outlets powered by the whole system, that's it).

I need to dig into the wiring in the junction box more...there are no labels on anything, so without power on it (what I'm trying to do), it is unclear what is what. But I just need to get in there and figure it out, probably using continuity.


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[G35Vortec454]

So it looks like you have one / main circuit breaker and that's it. Then for my troubleshooting suggestion above, instead of pulling individual fuses, you'll have to disconnect/reconnect black/hot load wire from the junction box one at a time.

 

[madmax718]

try this: take the battery out of the truck, attach inverter, plug in shore power line.

If it doesn't tripp the inverter fault light, then you've got some wacky wiring. that is connected to the battery.

floating neutral not so familiar with, but I know its not supposed to be good for a residential home!

 

[verdesardog]

All US Navy ships have floating neutral but I've never seen a GFI on any of them....