Factory Inverter Wiring

[HolmBase]

I have a 2021 Momentum 395MS with the factory solar package and have been incrementally upgrading our solar setup.

We've added additional solar panels, replaced the Jaboni components with Victron, replaced the lead acid with lithium...

Our next project is to replace the factory inverter with the Multiplus II 2x 120 and wondered if anyone here has done so and could share their experience.

I started poking around the wiring today and found the inverter sub-panel under the stairs and have a couple questions:

1. I have an email in to Grand Design requesting a wiring schematic but have yet to receive a response, does anyone here have one?

2. Can anyone explain how the sub-panel is wired? I can trace power back to the "opt inverter" breaker in the main AC distribution panel but am unable to follow the inverter wires that dive into the belly of the beast without taking my house apart.

Many thanks!

[Second Chance]

In the RV industry, schemiatics are a figment of our collective imaginations - but you may get a general block diagram. @SolarPoweredRV is one of our resident experts on this topic. Perhaps he can help you out.

Rob

[SolarPoweredRV]

I have a 2021 Momentum 395MS with the factory solar package and have been incrementally upgrading our solar setup.

We've added additional solar panels, replaced the Jaboni components with Victron, replaced the lead acid with lithium...

Our next project is to replace the factory inverter with the Multiplus II 2x 120 and wondered if anyone here has done so and could share their experience.

I started poking around the wiring today and found the inverter sub-panel under the stairs and have a couple questions:

1. I have an email in to Grand Design requesting a wiring schematic but have yet to receive a response, does anyone here have one?

2. Can anyone explain how the sub-panel is wired? I can trace power back to the "opt inverter" breaker in the main AC distribution panel but am unable to follow the inverter wires that dive into the belly of the beast without taking my house apart.

Many thanks!

In the RV industry, schemiatics are a figment of our collective imaginations - but you may get a general block diagram. @SolarPoweredRV is one of our resident experts on this topic. Perhaps he can help you out.

Rob

The reason Grand Design uses a "Sub Panel" when they install an inverter is because they do not/can not power the whole 120v system with their small Inverter (1,000 - 2,000 Watt).

I presume that you have the Residential Refrigerator and that is the only circuit powered by the OEM Inverter. To check this, simply disconnect from shore power and check all the 120v circuits to determine if any are powered by the Inverter.

I am not sure how Grand Design installed the Inverter, so, you are going to need to trace the wiring to find out. There are a couple of options: 1, they could have installed an Automatic Transfer Switch (ATS) that automatically disconnects the Sub-Panel from being powered by the Inverter whenever you are plugged into Shore Power. 2, they could ignore the fact that you are plugged into Shore Power and simply continue to power the Sub-Panel with the Inverter 100% of the time, essentially, your batteries are always powering the Inverter/Fridge from the batteries (which get replenished by the Converter when plugged into Shore Power). To determine which wiring method they chose, plug into Shore Power and turn off the Inverter, if your refrigerator stops working, then the Inverter is still powering your Fridge from the batteries even if you are on Shore Power.

Since you have a breaker in the main panel labeled "Opt Inverter" I am inclined to think you have an ATS that switches the source of Fridge power from the Inverter to the Main Electrical Panel when you are on Shore Power.

Note: You might consider keeping the OEM Inverter and ATS in place and wiring your MultiPlus II into the ATS instead of direct to the main Electrical Panel. Here is why: because you have the residential fridge, you need 120v power to the fridge all the time, if you keep the OEM Inverter and ATS in place only the Fridge will be powered while you are traveling versus the entire coach (if you turn off the MultiPlus II). Additionally, the 1,000 Watt OEM Inverter might be more energy efficient than keeping your 3,000 Water Inverter running 24/7. Another added benefit is that you would have a built-in backup Inverter if anything should ever fail. If you choose this route, ensure that the OEM Inverter gets turned off whenever the MultiPlus II is turned on.

Once you decide if you want to keep the OEM Inverter then you will have the answer to how you should install the MultiPlus II.

If you decide to keep the OEM Inverter operational, then you will need find out where the Shore power wires are connected to the Electric panel and ATS and run those wires as input to your MultiPlus II. Your Output wires are then connected to the same spots as the Shore Power wires were attached.

If you decide to eliminate the OEM Inverter, you will take the Shore Power wires as the input wires to the MultiPlus II and the output wires will go directly to the Electrical Panel (one line will feed 1/2 of the panel while the other wire will feed the other 1/2). You will then need to remove the OEM Inverter and Sub-Panel to wire the refrigerator direct to the breaker in the electrical panel (you will need to relabel the breaker from "Opt Inverter" to Refrigerator).


PS: Congratulations on installing your Solar System/Battery system in phases. This is a good way to not get overwhelmed by the scope of the project and to keep the project wallet friendly by spreading the cost over a few camping seasons.

It would be helpful if you posted a play-by-play on your build as an example of installing a system in phases.

Good Luck and please let us know what you discover once you get into the Inverter install.

[FT4NOW]

Note: this post is not complete, my power just went out in the house and my UPS is about to fun out, I will edit this when I get the power back on...

I find it ironic your house power turns off and your UPS is running out as you are replying to a thread recommending to turn off the power to the inverter. Hope everything works out OK.


I haven't traced the wiring in my 398 fully yet, but I don't have a dedicated sub-panel for our inverter. GD used empty breaker spots in the box and most likely disconnected the bus bar on the inside of the box. It's weird, I have an inverter breaker, then a separate main breaker that only controls a few loads with associated breakers. The main breaker I mentioned is separate from the actual main breaker. It was fun trying to figure out which breakers I needed on just to run my converter and fridge while plugged into my house.

[MoonShadow_1911]

I find it ironic your house power turns off and your UPS is running out as you are replying to a thread recommending to turn off the power to the inverter. Hope everything works out OK.

I haven't laughed this hard in a while!

To be clear, I'm not laughing at @SolarPoweredRV but at what @FT4NOW wrote.

[HolmBase]

Thank you for taking the time to offer your input! This certainly helped kick start some more thinking!

To your points above:

We do not have the residential fridge, I've had a couple Samsung refrigerators succumb to an untimely death in our sticks and bricks so I didn't have much faith in one lasting long getting pulled down the road full time. We have the Norcold 2118 and so far haven't had any issues other than replacing a couple internal fans. We try to harvest host or boondock as much as possible and the ability to run on propane sure takes a load off the batteries.

You are correct; I took another look in the front bay and found the ATS for the inverter circuit, it was hiding in plain sight. Our sub-panel has three circuits; Refrigerator, GFCI and General (which appears to be all remaining outlets).



I like the idea of leaving the factory inverter in place for some redundancy and really just simplifies the install.

Shore power -> ATS
Generator----> ATS
ATS---------> Multiplus
Multiplus-----> AC distribution panel

The sub-panel wouldn't know the difference as the circuits are essentially powered the same.

In regards to our system we started with the factory 320w panel and the Jaboni 30amp charge controller. Our first addition was a couple Lion energy UT1300 batteries in hopes of powering the fridge on moving day and leaving the propane off. It wasn't quite enough so we then added two more 320w panels and a Victron 150/100 with the smart shunt and Lynx distributor and two more UT1300 batteries. This is where things started getting real and had to really dig into the front bay and make the best use of limited space...

We have come to the realization on some extended dry camping trips we are still struggling with inadequate battery capacity and the ability to recharge them in a reasonable amount of time. Our 960 watts on the roof in the winter sun doesn't get it done and the generator charging through the factory converter is a joke.

I look forward to the Multiplus charging capabilities, powering more items with the inverter and the power share feature when mooch docking or on 30amp.

I still have much to do in regards to cleaning things up but this had been a work in progress...





The multiplus is test fitted above the generator enclosure, I don't really like it there but I don't have a lot of options as this model doesn't have a drop frame so the basement storage is nonexistent. I also just picked up a Cerbo GX so monitoring everything locally and remotely should be much easier.