Kevin Windrem avatar image
Kevin Windrem asked

Two Multi/Quatro system for RV accommodating in-phase legs

Not sure if this is a bug or a future request:

Multiple inverter/charger systems configured for split-phase power need to accept AC input with 0 degrees between the two legs.

The Ve.Bus System Configurator provides a selection for "Dual phase 180" and "L2 floating with return to original phase". But the the AC input is rejected if the two AC inputs are in phase.

"Floating" should accept the two AC inputs regardless of the relative phase.

Recently, there has quite a bit of discussion in other threads regarding the best way to configure Multis/Quatros for use in an RV with split-phase power inlets.

The complication arrises when split-phase power is not available. In this case, the RV must run off of a single circuit, putting the two inputs in phase.

There does not appear to be a configuration that will allow both Multis/Quatros to function with 0 degrees between their AC inputs. Rewiring the system for true parallel operation when moving between campgrounds is simply not practical.

Note that running a split-phase system on a single phase will never produce the double voltage (e.g 240 volts in the US). In most RVs however there are not any 240 volt appliances, or if there are, they would simply not function when on a 120 volt 30 amp service. This is a known and accepted situation.

Running both legs of a split-phase service in phase doubles neutral current. However, the total current available is lower than would be the case for a true split-phase service. For example, a typical RV in the US would have a 50 amp split-phase inlet. Running that inlet on a 120 volt 30 amp service would result in at most 30 amps on the neutral which is already sized fo 50 amps.

Power assist creates the potential for the Multi/Quatro output to produce greater than 50 amps of neutral current when running on a 0-phase service. This is easily handled by running separate neutral wires from each Multi/Quatro to the neutral busbar in the AC distribution panel.

multiple inverters
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2 Answers
john-ballman avatar image
john-ballman answered ·

The purpose of this information is intended to address the fact that campgrounds in the USA may provide 50 amp 240-volt split phase or 50 amp single phase shore power, and to allow the user to easily convert a duel multiplus configuration from split-phase to parallel configuration with a flip of a switch.

There are 4 components required:

  1. R1 which is a 240vac coil, SPDT 1 amp relay. R1’s purpose is to monitor the ATS output and go active if the incoming shore or generator incoming power is 240 volts. Pole #1 will provide 12vdc+ to a light located in the RV control box. Pole #2 will disable the active state of R2.
  2. Toggle Switch is a SPST make or break toggle switch that will activate R2’s 12vdc coil if the incoming power is not 2 phases, but parallel single phase. The light is to alert the user NOT to toggle the switch in the event of 240vac and R1 is a safety precaution if the toggle switch is accidentally toggled.
  3. R2 which is a 12vdc coil, SPST 50amp vac relay/contactor. R2 provides a transfer path between the two Multiplus outputs if the incoming power is single phase parallel feed. This will also activate L2’s multiplus output.
  4. The led light is 12vdc located next to the toggle switch which is to show that the incoming voltage is 2 phase 240 volts.

With this installation and utilization of the VRM, I can quickly convert from split phase to parallel configurations in less than a minute from inside of my camper. Additionally the required neutrals for the system are not shown for simplicity’s sake, and the parallel configuration doubles the load on the neutral, I suggest that the neutral from both multipluses are run to the neutral bus bar.img-0585.jpg

img-0585.jpg (495.9 KiB)
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Kevin Windrem avatar image Kevin Windrem commented ·

Very clever.

What happens if the multis are configured for parallel and presented with 120/240 shore power and visa-versa?

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JedTheFed avatar image
JedTheFed answered ·

Currently I have two multiplus wired in split phase. I have to use the Victron Connect software to load either a split phase or paralel profile before I can switch from a 30 amp to 50 amp plug or vise versa. Is it possible to do this with just a single SPDT switch and not reconfigure with victron connect?

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