Forum Discussion

joe6789's avatar
joe6789
Explorer
Oct 10, 2019

Wiring neutral/ground when splitting panel for MultiPlus?

Trying to install a Multi Plus Compact 2000w inverter/charger in my RV. The shore power connection has four wires: two 50A hot legs (red and black), neutral, and ground. Since the Multi Plus inverter will only power one hot leg, my plan is to "split" my existing breaker panel so that one leg (about half the panel) is powered direct from shore power and the other leg runs through the Multi Plus.

Let's say I leave AC line 1 as the non-inverter side, going straight from shore power into the breaker panel. Then AC line 2 would go from shore power, to the Multi Plus AC-in, then from the Multi Plus AC-out to the second leg of the breaker panel.

But how do I wire the neutral and ground?

Normally AC line 1 and 2 share a neutral and ground (since 1 and 2 are out of phase, their currents cancel each other out on the neutral). But now line 2 gets sent to the Multi Plus while line 1 goes straight to the breaker panel. Is it fine for the neutral and ground wires to simply follow line 2 through the Multi Plus before arriving at the breaker panel? Or does line 1 now need its own neutral/ground? Do I need to split the neutral so that one neutral wire follows AC line 1 into the breaker panel and another neutral wire follows AC line 2 through the Multi Plus? If so, do I need to isolate the two neutrals by cutting the existing neutral bar in the breaker box?

I've read that a better solution is installing a sub-panel, but I'm trying to go for the simplest solution, which I believe would be keeping everything in the existing breaker panel.

Advice would be much appreciated.
  • enblethen's avatar
    enblethen
    Nomad
    Oct 10, 2019
    The neutrals would be from different power sources and must be kept separate.
    The inverter neutral should (shall) be grounded where the shore power connection cannot be grounded in the rig and must be complete separate.
  • joe6789's avatar
    joe6789
    Explorer
    Oct 10, 2019
    enblethen wrote:
    Grounds can be on a shared buss. Neutrals must be on a separate buss.
    Your idea is a very bad idea! Your output from the inverter should be in a separate sub-panel. Leave the 50 amp shore power as is. Second leg normally powers other systems such as water heater, washer/dryer, or second AC unit.


    Enblethen, if line 1 and line 2 currently share a neutral bus, why must they be on separate neutral buses after the inverter is installed?

    Why do you say splitting the existing panel is a bad idea? It basically creates two breaker panels within the one box. Jack Mayer describes the method here (scroll most of the way down to "Splitting" a 50-ampere Load Center): http://www.jackdanmayer.com/Wiring.html
  • joe6789's avatar
    joe6789
    Explorer
    Oct 10, 2019
    larry cad wrote:
    All the grounds tie together. Keep in mind that a 2000 watt inverter can only supply about 15-16 amps. A #14 wire can carry that much so your concerns about overloading a neutral are unfounded. However, feeding half of your breaker panel is not necessarily wise. That is why most times the inverter has a separate feed from a 20 amp breaker in the panel, and the output from the inverter is fed to a "sub" panel. Keep in mind that your original panel is also a "sub" panel, meaning the ground and neutral are NOT bonded together in your panel because the ONLY permitted bond occurs at the campground service panel. Hope this helps.


    Larry, yes, the neutral and ground bars are not currently bonded and they will stay that way. Regarding the current level, there could potentially be more than the 15-16 amps -- when NOT inverting (when connected to shore power) the current still passes through the inverter to get to the breaker panel, and that could theoretically be up to 50 amps.

    Why is feeding half the breaker panel not wise? The method is described by Jack Mayer in the "Splitting" a 50-ampere Load Center here: http://www.jackdanmayer.com/Wiring.html . He warns against it if the inverter only has a 30 amp transfer switch, but my Victron MultiPlus has a 50 amp switch so that's not a concern.
  • enblethen's avatar
    enblethen
    Nomad
    Oct 10, 2019
    Grounds can be on a shared buss. Neutrals must be on a separate buss.
    Your idea is a very bad idea! Your output from the inverter should be in a separate sub-panel. Leave the 50 amp shore power as is. Second leg normally powers other systems such as water heater, washer/dryer, or second AC unit.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Oct 10, 2019
    Proper inverter install

    Main panel 30 amp branch----inverter---Sub panel--Inverter powered loads

    And that is how it's done on my RV... the sub panel powers the entainerment circuit (includes this computer) GFCI chain (Kitchen, bathrooms, patio and dining room table) and the microwave. Optionally (I added a manual transfer) the bedroom outlets and Fridge (same circuit) Original plan was to power fridge on electricity when driving ... Did nto work.. Powers fan while sleeping and charges phone though .
  • larry_cad's avatar
    larry_cad
    Explorer II
    Oct 10, 2019
    All the grounds tie together. Keep in mind that a 2000 watt inverter can only supply about 15-16 amps. A #14 wire can carry that much so your concerns about overloading a neutral are unfounded. However, feeding half of your breaker panel is not necessarily wise. That is why most times the inverter has a separate feed from a 20 amp breaker in the panel, and the output from the inverter is fed to a "sub" panel. Keep in mind that your original panel is also a "sub" panel, meaning the ground and neutral are NOT bonded together in your panel because the ONLY permitted bond occurs at the campground service panel. Hope this helps.

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