Hello, I have a 5th Wheel that is setup with a MP-II 12/3000 2x120v with a Cerbo GX. I have noticed a few times the Grid Icon will show a green arrow (see below). I believe this means its feeding back to grid. I do not want to do this. I have the MP programmed to “None” on grid code, No Assistants or Virtual Switches are used. Why is this happening?
I did noticed that in System Setup AC Input 1 was set to “Grid” instead of “Shore” and that AC Loads was set to “Input and Output” instead of “Output Only.” Would this affect anything?
Double check your wiring. If you have grid code “other” then the back-feed relay isn’t going to be engaged. Did you at some point ever change the grid code from none to something else and then back? It’s not likely you did that, so I think you have something weird going on with your chassis bonding as a “ground”. Or you have a neutral-ground bonding issue.
Did you have this professional installed or was this a DIY project?
So… I am the professional… so trying to figure this out on here. I guess the tag should have said as much.
But as far as I know the wiring is correct. Split phase 50a RV with Onboard Generator. Both input sources go through a 50A Transfer switch, then into the MP-II. Then into the AC Panel where the ground bus bar is connected to chassis grounded.
Programming:
-Ground Relay Checked
-Grid Code has always been “None”
-No VS, No Assistants
-Working on updating to v555 firmware, currently on v510.
I believe it might just be a zero point error as Ludo mentioned.
I hope that’s the case. I’ve not seen this happen before on these kinds of installations, but it could be just as he says or maybe a quirk in the FW or new UI.
Double check that you haven’t bonded neutral and ground in the transfer switch. The Onan generators are typically N-G bonded and of course the shore power connection should have N-G bonding. The relay setting enables the N-G relay on the Multi when no AC input is connected.
If you also have a N-G bond somewhere else on the AC input side then you could possibly see weird behavior like this. I’m not saying it’s a certainty, but when I see wonky behavior like this on the input or output side 9 times out of 10 it’s a grounding or N-G bonding issue.
Please reply back and let us know what the result is. It’s good learning for all. Thanks!
Updated to v555. Still no luck. I am not local to the customer right now, so I cannot verify Transfer switch or Generator wiring, but I would be extremely surprised if there was a N-G wiring issue. I think at this point its a quirk of the new GUI/Venus OS.
Next time I have the system in hand, I will verify wiring and software as needed.
