30 amp plug in a 3000 watt inverter?

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Gary RV_Wizard

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Agree, Wally. Looks like it was designed to accommodate an ATS, but none is there.

Where do those two orange-sheathed wire bundles go to? Is one of them the shore cord connection? And the other that outside box shown in post #8? How does power get from that box to the 30A load center?
 

Oranjoose

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Agree, Wally. Looks like it was designed to accommodate an ATS, but none is there.

Where do those two orange-sheathed wire bundles go to? Is one of them the shore cord connection? And the other that outside box shown in post #8? How does power get from that box to the 30A load center?

I don't think I explained it very well before. Maybe this labeled picture might help.

IMG_20210415_170901__01.jpg

The orange-sheathed cable labeled with the blue arrows comes from the outside box pictured in post #8. It goes into that metal box behind the wall.

The black cable labeled with red arrows is the shore cable. You can't really see it behind that wood block below, but it also enters that metal box behind the wall.

The orange cable labeled with yellow arrows comes out of that metal box behind the wall and goes behind the power center, ultimately connected to the Main 30 amp breaker.

Is there not an ATS in that box? It seems there must be some kind of switch going on in there, right?
 

Old_Crow

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Not sure they'd go to the expense of adding the switch unless it had the generator.
You really have to access the box and open it up, anything else at this point is pure speculation.

That being said, I suspect you'd find the shore cord tied to the romex labeled in yellow(going to the power center)and the romex labeled in blue just capped off. If the blue line was actually tied into the wiring inside that box, it would be hot with 120v back near the generator compartment when the coach was plugged in to shore power. Not a good thing.
Although, I do suspect the ground wire in the blue set is probably screwed to the box like it is at the other end.
 

Gary RV_Wizard

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If the blue line was actually tied into the wiring inside that box, it would be hot with 120v back near the generator compartment when the coach was plugged in to shore power. Not a good thing.
That was my thinking as well. Earlier it was stated there was only 500 mv on that box/wire when plugged to shore power, but maybe that was inaccurate? It also said there was a slight change in the voltage there when no shore power at all.

Not a good thing.
Potentially a very unsafe thing unless great care is taken to have no exposed connections (male plugs). Shore power backfeeding into the wiring or the generator itself is scary. There are ways this could be done safely, e.g. a relay is installed to open the generator circuit if not in use (aka, an auto-transfer switch). A 30A auto-transfer switch would have been simple and cost-effective. Or even a manual DPDT switch.
 

Oranjoose

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That was my thinking as well. Earlier it was stated there was only 500 mv on that box/wire when plugged to shore power, but maybe that was inaccurate? It also said there was a slight change in the voltage there when no shore power at all.


Potentially a very unsafe thing unless great care is taken to have no exposed connections (male plugs). Shore power backfeeding into the wiring or the generator itself is scary. There are ways this could be done safely, e.g. a relay is installed to open the generator circuit if not in use (aka, an auto-transfer switch). A 30A auto-transfer switch would have been simple and cost-effective. Or even a manual DPDT switch.

I managed to open up the metal box behind the wall, and this is what I found:

img_20210417_171941-jpg.145671


Definitely looks like an automatic transfer switch. I think the underside of the lid gives it away:

IMG_20210417_172040.jpg

I guess I still don't know for sure that it's all been wired up. I mean, it'd be pretty lame if they wired the inlet into this ATS, but then capped it off inside without actually wiring it. The wires are really densely packed, so it's hard to see, and I am nervous to mess around in there, because even though shore is disconnected, who knows how long this thing holds energy?

One piece of the puzzle I forgot to mention is that I stripped off more of the wire in the inlet box and pressed the multimeter probes harder against the conductors and measured a consistent 3.1 Mega-ohms between live and neutral (while shore was disconnected and Main break switched off). I'm definitely not an electrician, so I don't know what that means exactly, but maybe it has to do with how the ATS is detecting a load in order to switch power sources?

My last question for now is, supposing that this inlet is all wired up correctly with the ATS, can I install a common 30 amp RV receptacle (Nema TT-30R) into that inlet box, and then fashion a 30 amp cable to the inverter and have that plugged into the inlet receptacle? Would that work?
 

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Old_Crow

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Sure, but then you'd end up powering the entire coach off that inverter. If that's your goal, don't forget to at least unplug or throw the breaker for the converter so you don't get into a charging loop.

Just a note about running a big 30 amp coach on solar:
We camp hosted at a spot that only had a solar setup for host power. It was 8 or 10 giant panels on a pedestal with tracking capabilities, 8 big batteries(new that year)and a giant inverter. There was also a backup generator tied in for cloudy days.
Just plugged the coach into this setup like a normal power pedestal. Worked fine during the day(altitude was around 7500' so we never needed the a/c's the whole summer), but by 8pm most nights the solar batteries hit the low voltage threshold and the TV went off...usually in the middle of a good show and 3 hours before our normal bed time.
We ran the fridge on propane the whole summer, shut the countertop ice maker off at dusk, and did everything we could to reduce 120v usage, but there it was. I hated waiting for the 6 am generator hours in the morning to brew my coffee when I normally rise at around 4:30.
 

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