Charging RV with inverter running

[Butcher]

I did a search and I did not find the exact information I am looking for.

I have a 50A 5th wheel. I have an auto transfer switch and the inverter will be powering one leg of the 50A circuit. The other leg is not being used. The leg not being used supplies power to the second A/C, 100A converter, fireplace, etc. Basically everything I do not really need when the inverter is on.

I believe the white wire [neutral] is still switched with the transfer switch is engaged. The hot wire is what is not being switched. Is it possible to run shore power to that leg so the converter could be charging the batteries [not interested in using the other consumers on that leg] or will the common neutral be effected in a way that the inverter will not work or be ruined.

I guess in simple terms can a common neutral be used for two different phases on A/C power?

Sorry if this has been asked before, but I honestly searched and my skills may not be up to par with others.

 

[John Frum]

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[John Frum]

I believe the white wire [neutral] is still switched with the transfer switch is engaged.

Does that mean the neutral is switched with the hot(s)?
Is the ATS split phase?
I've never seen an ATS that doesn't switch the hot(s).

 

[time2roll]

Generally both hots and neutral switch together and will be getting power from the inverter input only. The second hot will not be powered if the inverter is not connected to provide the power. The utility cord is fully isolated and will not provide power to the RV main panel until the inverter is switched off.

I recommend a separated charger or converter to be powered through a separate extension cord to the pedestal or generator. This will put power direct into the battery independent of other systems.

 

[Butcher]

I wired the transfer switch up and it's basically back together so I'm not willing to take it apart to take pictures of the transfer switch.

How it is hooked up now is that there are two hot leads shore power, 1 neutral shore, and one ground shore. The inverter only uses one of the hot leads, neutral, and ground. When the inverter is on, it transfer switch turns on, it will transfer both hot, neutral, and ground but there is only one hot that is live. The other one has nothing hooked to it.

If I power up the second circuit with shore power, shore neutral, and shore ground, will the inverter get upset with another phase on the neutral circuit?

I thought about using a second converter or even get a separate transfer switch for the converter I already have. That will be my plan B if I cannot do what I'm thinking about.

 

[TacomaJoe]

Not sure about the reason to do this. If you're running on the inverter, then I'll assume no shore power. If you do have limited shore power and want to keep the batteries charging, then I agree that the simple way would be a separate charger.

 

[Butcher]

Run a generator to charge the batteries while the rest of the 5th wheel is working on the inverter. That is the reason.

The generator I have is small. It certainly would not keep up with the 5th wheel. The 3k inverter should. The 5th wheel would never run 3k for hours so I believe the small generator could charge the batteries once they get low.

I understand this may not be something others think about, which is why I could not find what others have done.

 

[time2roll]

Yes I do same. I have a small 700w propane generator for if situation gets difficult. I have a separate 25 amp power factor corrected charger ready to deploy when needed. Even my small 35 amp converter will overload the generator due to poor power factor needing 30% additional apparent power.

 

[TacomaJoe]

I get the plan. So the generator that you mention isn't trying to take over from the inverter is it? I don't have have any transfer switches in my rig so I'm not 100% on their operation. My fix would wire the converter to a transfer switch so that normally it gets power from the shore cord. When the generator fires up it would transfer the converter circuit from shore power to the generator. It might be easier to get the whole leg #2 circuit to transfer and as you say just don't use the other loads.

 

[time2roll]

Is it an on-board generator? Or portable? Split phase? 120v only with 2 hots?

With an on-board generator it would generally have its own transfer switch to the utility cord and bypass the inverter. When the generator is shut down the inverter would take over.

Hard to know what is needed until we know what the system is and what needs to be accomplished.

 

[Butcher]

Basically, I need to know if I run one leg with an inverter can I run the other leg on either shore power or a small generator at the same time. The only thing in common would be the neutral leg. Can the neutral leg accept the AC signal from the generator and inverter at the same timing. The legs would not be in phase since they are coming from different sources.

I would like to keep the 5th wheel working with the batteries and the small generator supplying the second leg [that would keep the converter charging the batteries].

I understand that if I unplug the converter and plug it into the generator, that would suit my purpose but I would rather supply power, neutral, and ground to the second leg and not screw up the first leg. The only thing in common would be the neutral and ground.

Sorry if I'm not making myself clear.

 

[time2roll]

I believe having two sources with a shared neutral is the wrong thing to do.

 

[Butcher]

That is what I was thinking but I have yet to read that. In theory, the electrons that go in/out of the inverter would know where they go back to, as well as the source power. So, I think it would work.

I do know that you cannot share the hot leads. The frequency patterns must match.