Multiplus II 120x2 with onboard generator wiring confusion

[WattsItToYa]

I'm trying to wrap my head around how this works...

Class A RV with a 50 amp split phase breaker panel and a Onan 5500 watt onboard generator- so 120 volt/45.8 amps max output. The generator has (2) 30 amp breakers on the control panel. Each breaker with #10 wire feeding each side of a 50 amp receptacle (no transfer switch)- I have to plug the shore power cord into the receptacle when I want to use generator power.

(Odd observation- I noticed the wires coming from the generator go into a j-box near the generator- each leg coming from the generator breakers has it's own neutral wire but then the neutrals combine in the J box then has 1 neutral wire and 2 hots from the j-box going to the 50 amp receptacle?)

So the generator wiring is essentially acting like a 50/30 amp dog bone adapter and feeding the same 120 volts thru both legs to the 50 amp plug....right?
So I'm getting a max of 22.9 amps/120 volts at max generator output to each side of the receptacle and hence to each side of the split phase breaker panel...right? (I measured generator voltage output today with no load and it was 119 volts)

I'm getting ready to run the 6/3 romex 120V power wiring from the shore power cord J-box to the Multiplus location and then a second run from the Multiplus back to the J-box feeding the breaker panel. Just confirming I do not need to install a transfer switch because the generator wiring is already combining the two legs of power together....right?

So the Multiplus will "know" if it is getting actual 240 volt from a shore power pedestal connection VS a combined 120 volt from generator power...right?

When I set the Multiplus amperage setting so it knows how much amperage is available on a real 240 volt 50 amp service I can set it at 50 amps....right?
Is pedestal 30 amp usually 120 volt of 240 volt? So Multiplus set for 15 amps or 30 amps?
Then when I'm on generator power would I set it at 22.9 amps or 45 amps?
(I know- actually reduce setting by a few amps to prevent nuisance tripping)

How wrong do I have it? Lol

 

[sunshine_eggo]

I'm trying to wrap my head around how this works...

Class A RV with a 50 amp split phase breaker panel and a Onan 5500 watt onboard generator- so 120 volt/45.8 amps max output. The generator has (2) 30 amp breakers on the control panel. Each breaker with #10 wire feeding each side of a 50 amp receptacle (no transfer switch)- I have to plug the shore power cord into the receptacle when I want to use generator power.

(Odd observation- I noticed the wires coming from the generator go into a j-box near the generator- each leg coming from the generator breakers has it's own neutral wire but then the neutrals combine in the J box then has 1 neutral wire and 2 hots from the j-box going to the 50 amp receptacle?)

So the generator wiring is essentially acting like a 50/30 amp dog bone adapter and feeding the same 120 volts thru both legs to the 50 amp plug....right?

Because you said wiring, no. The generator is wired to the L1, N and G (as applicable) MP-II input. Nothing is wired to L2.

The unit automatically passes through the same phase to both legs like 30A power when single phase power is sensed.

So the inverter/charger is acting like the 50/30 amp dog bone adapter.

So I'm getting a max of 22.9 amps/120 volts at max generator output to each side of the receptacle and hence to each side of the split phase breaker panel...right? (I measured generator voltage output today with no load and it was 119 volts)

If you have the generator wired to both L1 and L2, that's wrong.

I'm getting ready to run the 6/3 romex 120V power wiring from the shore power cord J-box to the Multiplus location and then a second run from the Multiplus back to the J-box feeding the breaker panel. Just confirming I do not need to install a transfer switch because the generator wiring is already combining the two legs of power together....right?

Do you not already have a transfer switch? to auto select shore vs. gen? You need some sort of transfer switch to ensure both sources are never connected at the same time.

Shore L1, N, L2, G to ATS input 1 L1, N, L2, G
Generator L1, N, G to ATS input 2 L1, N, G (if there are two separate outputs, they should both go to L1)

ATS out L1, N, L2, G to MP-II L1, N, L2, G input.

MP-II output L1, N, L2, G to AC panel L1, N, L2, G

So the Multiplus will "know" if it is getting actual 240 volt from a shore power pedestal connection VS a combined 120 volt from generator power...right?

THe MP-II senses whether it is fed 120/240 split phase or single phase power.

When I set the Multiplus amperage setting so it knows how much amperage is available on a real 240 volt 50 amp service I can set it at 50 amps....right?

Yes

Is pedestal 30 amp usually 120 volt of 240 volt? So Multiplus set for 15 amps or 30 amps?

"30A" is 120V, 30A. Set input to 30A

Then when I'm on generator power would I set it at 22.9 amps or 45 amps?

45A

 

[WattsItToYa]

Thanks for the reply!....

1) There is no transfer switch- just a receptacle so there is no way to connect grid power and generator power at the same time.


2) The generator is set up so one leg feeds L1 and one feeds L2 on the receptacle. So essentially when I plug my shore power cord into the receptacle it is the same as if I were using a dogbone adapter and plugging into a 30a pedestal.... right?

This diagram is from Onan (Cummings). Mine would be most similar to the bottom diagram except I have a receptacle instead of the transfer switch. I think the reason there are two neutral wires coming into the Jbox closest the generator is in case it were to be connected like the top diagram- with one leg going straight to an a/c unit and one leg going to the breaker panel.



My next concern would be regarding the neutral ground bonding. I know the Multiplus has a switching relay in regard to the n-g bonding when running on generator power. Not sure how that will work considering my seemingly unconventional generator set up?

But in general I don't think not having an ATS is a bad thing is it? It seems pretty fool proof and reliable. I will mostly be boon docking so I don't feel it will be any inconvenience for me to have to physically unplug from generator and plug into shore power when needed.

Just trying to avoid having to move my thread to the "Up in smoke.....Learn from my mistake!" thread when I connect up my Multiplus.

Again....thanks for any input!

 

[sunshine_eggo]

Thanks for the reply!....

1) There is no transfer switch- just a receptacle so there is no way to connect grid power and generator power at the same time.
View attachment 285532

AH!!! So you plug your shore power into the "50A" outlet from the generator (shown above). I had a 30A RV with that too, and forgot about that option.

2) The generator is set up so one leg feeds L1 and one feeds L2 on the receptacle. So essentially when I plug my shore power cord into the receptacle it is the same as if I were using a dogbone adapter and plugging into a 30a pedestal.... right?

I would re-wire both generator legs exclusively to L1.

This diagram is from Onan (Cummings). Mine would be most similar to the bottom diagram except I have a receptacle instead of the transfer switch. I think the reason there are two neutral wires coming into the Jbox closest the generator is in case it were to be connected like the top diagram- with one leg going straight to an a/c unit and one leg going to the breaker panel.

View attachment 285533 View attachment 285538View attachment 285543View attachment 285544View attachment 285545 View attachment 285542

My next concern would be regarding the neutral ground bonding. I know the Multiplus has a switching relay in regard to the n-g bonding when running on generator power. Not sure how that will work considering my seemingly unconventional generator set up?

The MP releases its N-G bond when fed AC input. If your generator does not provide N-G bond, you will not have a N-G bond and may have a hot skin.

 

[WattsItToYa]

I would re-wire both generator legs exclusively to L1.

??? I was looking at this wiring diagram from a Progressive Dynamics xfer switch and it shows the generator hots both connecting to L1 and L2. Its not specific to my generator but I assume it is a 120 volt generator...so this would be the same as plugging the shore power cord into my generator receptacle the way its wired now.
I'm thinking the Multiplus will sense that it is the same 120 volt input on L1 and L2 and respond accordingly? IDK

The MP releases its N-G bond when fed AC input. If your generator does not provide N-G bond, you will not have a N-G bond and may have a hot skin.

Looks like it does show the n-g bond on the diagram so I should be GTG.

 

[sunshine_eggo]

??? I was looking at this wiring diagram from a Progressive Dynamics xfer switch and it shows the generator hots both connecting to L1 and L2. Its not specific to my generator but I assume it is a 120 volt generator...so this would be the same as plugging the shore power cord into my generator receptacle the way its wired now.

You keep referencing diagrams, but I don't see any that pertain to a 2x120V MP-II.

I'm thinking the Multiplus will sense that it is the same 120 volt input on L1 and L2 and respond accordingly? IDK

I'm not confident at all, I don't think it will cause any problems, but when on generator, and you want to charge, and when on generator, you want to charge as fast as possible, you will only charge from the L1 leg.

I would rather be able to charge with 40A instead of 20A.

You can try it as-is and see what happens. If you only get 20A of charging, then you'll want to wire it as I recommended.

Looks like it does show the n-g bond on the diagram so I should be GTG.
View attachment 285561

I can't read that diagram, but I'll take your word for it. I would expect it to since RV generators should provide it given the configuration.