Split 50a cables for parallel inverters

[jledwards0117]

I am adding a 2nd Victron Multiplus-II 12/3000/50 2x120 to my 5th wheel and will parallel the two inverters. I know from Victron documentation and from reading many threads on this forum how the wiring should be run, but kindly ask some guidance on the specifics of how to split the incoming 50A AC 6/3 cable (B-R-W-G wires) into two cables going to the inverters and, similarly, how to combine the output cables into one going back to the main breaker panel.

In other words, what type of splitter or combiner or breaker apparatus would I use in the junction box to make these connections and, hopefully, keep the footprint as compact as possible since we are talking about an RV? I just need to know what to ask for or order to get the right equipment for the project.

TIY,
Jim

 

[DIYrich]

Busbars - Victron Energy

Busbars are used for high current distribution and at the same time they provide connections for batteries and/or DC equipment. We offer a number of...

www.victronenergy.com

DC Distribution systems & Fuses - Victron Energy

Victron Energy's DC distribution systems monitor the state of charge of your battery and the state of each fuse. View products now.

www.victronenergy.com

 

[#40Fan]

Run your incoming 240 into a panel and add two 120 volt breakers, making sure each breaker is fed from a different leg of the 240. From those 120 volt breakers to the inverters.

Connect the out going wires from the inverters to another panel's 240 volt in, and run your loads from that panel with added breakers.

Edited to add: You likely already have a panel that the incoming 240 volt attaches to. You could remove all of the loads from that panel (heater, stove, microwave, etc) and use two 120 volt breaker inside of it to run to the inverters. Add a second panel that you will now attach your loads back into, and run your inverter into it.

 

[MisterSandals]

Connect the out going wires from the inverters to another panel's 240 volt in, and run your loads from that panel with added breakers.

Asking because I do not know:
Without incoming grid 240 (2 legs, split), how do the 2 Multipluses know what the others’ phase is?
Doesn’t there need to be some connection/communication between the two?

 

[#40Fan]

Isn't that how all paired inverters work? Tied together with communication cables.

 

[MisterSandals]

Isn't that how all paired inverters work? Tied together with communication cables.

I thought so, I just did not see a mention of it and the wording, to me anyway, suggested there might not be such a communication cable.

 

[jledwards0117]

For those who asked, yes, the two inverters will be connected by an communication cable so that they can sync to one another. My only issue with the setup is how to split the feed and output cables so that each inverter gets both hot wires, a neutral and a ground.

Jim

 

[MisterSandals]

...hmmm, rethinking my comment.

 

[DIYrich]

For those who asked, yes, the two inverters will be connected by an communication cable so that they can sync to one another. My only issue with the setup is how to split the feed and output cables so that each inverter gets both hot wires, a neutral and a ground.

Jim

https://www.grainger.com/product/POLARIS-Insulated-Multitap-Connector-34UH88

 

[DIYrich]

Asking because I do not know:
Without incoming grid 240 (2 legs, split), how do the 2 Multipluses know what the others’ phase is?
Doesn’t there need to be some connection/communication between the two?

One inverter has to be designated the "master". It will be the grid forming inverter. The rest will follow, just like being grid connected.

The communication cable is to moderate production (which unit is producing how much), charging, etc.

 

[jledwards0117]

Run your incoming 240 into a panel and add two 120 volt breakers, making sure each breaker is fed from a different leg of the 240. From those 120 volt breakers to the inverters.

Connect the out going wires from the inverters to another panel's 240 volt in, and run your loads from that panel with added breakers.

Edited to add: You likely already have a panel that the incoming 240 volt attaches to. You could remove all of the loads from that panel (heater, stove, microwave, etc) and use two 120 volt breaker inside of it to run to the inverters. Add a second panel that you will now attach your loads back into, and run your inverter into it.

According to Victron, both legs of the incoming power (plus neutral and grounds, of course) need to go to both inverters. The two 120v breakers, as you described in your post, would not make that kind of connection. Similarly, the output from each inverter (both hots, neutral and ground) must be combined to go back to the main breaker panel.

 

[jledwards0117]

https://www.grainger.com/product/POLARIS-Insulated-Multitap-Connector-34UH88

Yes, I found those connectors but thought there would be something more straightforward (and less expensive) for making a jumble of connections like this. This would require 4 of those connectors for the AC in cable and 4 connectors for the combining of the AC out cables back to the load center, and I see no way to fasten them down in a junction box or otherwise, except maybe quick-ties.

 

[#40Fan]

From what I've read, the Victron can be used in both 120V and 240V modes. Wire it like I said, and when paralleled, you'll have 240V of output.

BTW, I was also thinking that if you want to only use the panel you have now, you could install a 240V bypass breaker with an interlock. Run your power from both inverters back to the panel using that breaker.

Install another single 240V breaker to power the inverter when you want to charge batteries with shore power.

The wiring would be about the same as before, minus the extra load panel.

240V breaker fed by shore power -> One leg to Inverter 1 - One leg to Inverter 2

One output leg from Inverter 1 and One output leg from Inverter 2 -> 240V bypass breaker

 

[jledwards0117]

From what I've read, the Victron can be used in both 120V and 240V modes. Wire it like I said, and when paralleled, you'll have 240V of output.

BTW, I was also thinking that if you want to only use the panel you have now, you could install a 240V bypass breaker with an interlock. Run your power from both inverters back to the panel using that breaker.

Install another single 240V breaker to power the inverter when you want to charge batteries with shore power.

The wiring would be about the same as before, minus the extra load panel.

240V breaker fed by shore power -> One leg to Inverter 1 - One leg to Inverter 2

One output leg from Inverter 1 and One output leg from Inverter 2 -> 240V bypass breaker

Thanks for the input. I plan to follow Victron's suggested configuration for the wiring so I will follow a version of your recommendations. I plan to install a small panel with 2 double-pole 50a breakers, in order to split the feed for each inverter. Then, I'll do a separate subpanel to combine the two outputs back to the main breaker panel.

Panels will take up more real estate than I had hoped but they will be up to standards and will accomplish the goals.

Thanks again for your help. I really appreciate it.
Jim

 

[DIYrich]

I see no way to fasten them down in a junction box or otherwise, except maybe quick-ties.

Buy Triple Wire Lugs (3 wires per lug, at LugsDirect.com

Buy triple wire triple barrel terminal lugs. Allow 800 kcmil to 14 AWG copper or aluminum wire, and are CSA certified and UL listed. Aluminum with tin plating. Made in the USA from domestic and imported parts

lugsdirect.com