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Just ordered my multiplus ii 2x120 (currently being shipped to me) and now I found out it will be an issue with my onan 5500 in my toy hauler 5th wheel. I’m on shore power about 10% of the time so this will obviously be an issue when boondocking. I read there is a work around but haven’t seen any concrete information. I asked the question to my Victron dealer but haven’t heard a response. Can someone please advise?
The MultiPlus ll 2x120 can do standard split-phase 120/240VAC, with 180 deg phase angle between L1 and L2 input. This is commonly 240V exactly.
This can range to 180-280VAC between L1 and L2. This is approx. a 120 deg phase angle of 120V lines , which is two legs of a 3ph supply, but accommodates for individual line voltages in the range of 90-140VAC.
If the MP 2x120 senses only 90-140VAC on input, it will only allow L1 to connect (The min/max input is adjustable to a finer range with software), as this is considered a 1ph supply voltage range.
The blocking of L2 when a 1ph supply voltage range is detected is intentional, as the MP 2x120 measures the phase shift in order to calculate the current passing through the neutral.
When the phases are in sync, this can no longer be measured, which could potentially be dangerous, as more current could pass through the unit than it was designed to handle.
Theoretically, allowing in phase lines to pass through the MP 2x120 could be possible through a software update, but only if there can be a guarantee that the unit would not see current above what the relays and internal wiring are designed to handle.
Victron does not seem to have a solution at this time, but they are aware of the issue here and brainstorming ways to resolve this.
Best,
Caza G.
For my Onan 5500 I just took the L1 and L2 hots and combined (parallel) them into L1 on my ATS. My ATS will work with only L1 hot. You'll note that L1/L2 from the genset are really just 2 - 30A circuits in phase and share the neautral. Neutral should alread have been sized to carry both circuits which will max out at 46A on the 5500 (not 30A + 30A of the breakers). But with the 25A boost from MP2 you'll achieve +/- 70A shared by L1/L2. The finished product is actually producing more available amperage than the genset alone.
This works great for RV panels that use no 220v distribution breakers.
PS - if your ATS doesn't work w/o power to L2, just add a jumper from L1 to L2 (I'd recommend removing the jumper on the L2 output side of the contactor that jumps L2 to L2 on the output side of shore and genset contractors).
It depends on the output configuration of your generator. If it is 120 volts, then the Multi will see it as such and switch the output to two legs of 120 volts with 0 volts between them. Generally OK in an RV unless there are 240 volt loads.
This is also what happens when there is no shore power or generator.
If the generator output is 120/240 split phase (180 degrees between legs), this would work also with the Multi. L2 will pass through the Multi. L1 will benefit from the inverter assist.
If your generator has two 120 volt outputs that are in phase, then you would only be able to connect one of these outputs to the Multi. I seem to recall from another post that there might be a modification to the Onan 5500 generator to change it’s output to something more compatible.
Have read through other posts regarding it, but no resolution.
Shaner,
My answer above is based on running shore power and genset to ATS and then the ATS output to the MP2 2x120. That is my configuration (alomg with the changes in my other post.
