Victron MultiPlus 12/3000/120

[jbailey]

All,
I am doing the research on a charger/inverter and was thinking about the Victron MultiPlus.
https://www.victronenergy.com/invert...48v-800va-3kva

But I have a question: the Pass Through/Auto Transfer switch is only 50 amp, does this mean I would need two of them to handle each leg of the 50 Amp service (really 100Amp) coming into the trailer?

Thanks in advance for any advice/knowledge you share.

Ben

[Wizbangdoodle]

If the inverter has provisions for both L1 and L2 then that should be all you need.

[Luv2Ski]

Chris and Cherie at Technomadia.com use this unit as the house inverter on their bus conversion. They have online blogs about it and are pretty responsive to questions. This summer I plan to install that same unit myself and would like to know what you find out.

[carnolddsm]

It only handles one leg.

Here is a link to our installation

http://www.mygrandrv.com/for...Momentum-397TH

[jbailey]

Steve, I reached out to Victron and confirmed that its only Single Leg. Colan's post describes the difficulty in splitting the dual leg RV input to a single leg branching out to two locations. As of now, I plan on doing something similar to Colan, but without the transfer switch as I don't have a generator.

Colan, thank you for the link to your post. I would love to see some more pictures of your instillation of the MuliPlus, if you have them.

Thanks, Ben

[Luv2Ski]

My MultiPlus will be fed by L1 from the factory transfer switch. I'll have to contact Victron to get the sync time spec - the time it takes to sync the inverter output frequency and phase to the sudden appearance of AC coming from the factory transfer switch. In my case, the power from the factory transfer switch comes from either shore power or from the 5KW Onan genset. It could be split phase or L1 & L2 bonded together depending on the type of shore power.

Regarding splitting the dual leg through the load center and what that means to the neutral leg currents, here's my analysis:

1) When hooked to a 3-wire split phase source (i.e. 50A shore power or in my case, the Onan 5KW genset) L1 & L2 will be 180º out of phase with 220v potential between them. Each does have a 110v potential to the neutral of course.

2) When hooked to a 2-wire 110v source (30A RV service, 20A or 15A), L1 & L2 are effectively bonded and in phase. They should have no significant voltage difference measured between them beyond the usual IR drop. They do have 110v potential to the neutral of course.

3) Since I will never have any 220v appliances that use L1 & L2 together when on split phase power there are no concerns here relating to load center splitting.

4) In all cases before an inverter is added to the mix, the current flowing on the neutral conductor is the vector sum of currents flowing on L1 & L2. In 3-wire 50A split phase, the vector sum is L1 amperage minus L2 amperage because they are 180 degrees out of phase. When hooked to 2-wire power (i.e. 30A, 20A or 15A) the neutral current is L1 amperage plus L2 amperage because they're in phase. If you think about it, the highest current that would theoretically appear on the neutral is 50A in the 50A split phase shore power scenario and that is assuming current is flowing over just L1 or just over L2 - very unlikely. It also assumes resistive loads for simplicity (A/C units are not pure resistive loads and therefore the peak current could be somewhat higher).

5) Introducing the Victron Multiplus charger/inverter, let's assume it's fed by L1 and let's refer to the inverter output as L1a which is normally in sync with its L1 input (from shore power or genset) when present. It's not germane here but the inverter is powered by the battery bank plus any other active DC source such as solar or wind. A very important distinction in this case is that the neutral current would now be the vector sum of L1, L1a and L2. The 3KVA MultiPlus inverter can provide 2.5KW continuous @ 75ºC into a resistive load. That's about 23A @ 110v. Our new worst case neutral current would occur when on 50A shore power and L1a is synced to L1, shore is supplying L1=50A, L1a=23A (from battery + solar + wind) and L2=0A. This yields a total neutral current of 73A steady state. If there is any current on L2 or if L1a is at any other phase other than 0º to L1 (as would briefly be the case the moment shore power is connected) the vector sum of currents traversing the neutral would be less than 73A.

For 2-wire shore service, the current from L1 & L2 is limited to the supply source's amperage. So worst case neutral current is L1a is synced to L1 with total neutral current equaling L1+L1a+L2. Since L1 + L2 can be no more than 30A the total current on the neutral is 30A ++23A from L1a when the inverter is drawing from its DC source. That's 53A steady state.

If the neutral is sized right, there will be little IR loss to cause any side effects to loads from other legs. Loads connected on L1a will see a phase shift occur during the sync up period when shore or genny power comes online.

Hope this makes sense. I still need to think through how the MultiPlus will get configured and whether or not it belongs downstream of the load center driving its own sub panel or just how this should work. Neutral bonding to ground also needs to be done right and that changes depending on where the power is being sourced. Bonding should be external to the RV for shore power I believe and at the genset when it's powering the rig. When only the MP inverter is running with L1 cold, should it bond neutral to ground.

[emcclure]

I still need to think through how the MultiPlus will get configured and whether or not it belongs downstream of the load center driving its own sub panel or just how this should work. Neutral bonding to ground also needs to be done right and that changes depending on where the power is being sourced. Bonding should be external to the RV for shore power I believe and at the genset when it's powering the rig. When only the MP inverter is running with L1 cold, should it bond neutral to ground.

I’m planning to install the same Victron inverter/charger in my rig and would love to know what you decided on here. This remains the one big open question to my design as well: Does the Victron need to drive it’s own sub panel, or can it sit between 50 amp shore power and the main AC panel?

Thank you in advance!

[offtohavasu]

Go Power has a unit that will do 50 amp pass through on both phases if that's what you're looking for.