AC Break Panel Mods for Dual Main Breakers

[Casa_Woody]

A few months ago I had a 600W solar system and a 3000W inverter installed with 4 BB 100Ah batteries.
The inverter is a Victron MultiPlus-II 2x120V Inverter/Charger. This inverter has an AC OUT 1 and an AC OUT 2. OUT 1 provides AC power whenever connected to shore power or when inverting. OUT 2 is only active while on shore power. The idea is to connect loads that you don’t want on inverter power to OUT2, i.e. the air conditioning units, thus saving your battery power for the essential loads such as the refrigerator and TV.



In my current setup I am not using OUT 2, all loads connected to OUT 1. I’ve come up with a what I believe to be a very clean way of splitting my AC power panel into two segment.

The power panel is a Progressive Dynamics PD55K000 (1 main breaker with 8 slots (16 circuits). PD shows an alternate configuration called the PD55K005 (2 main breakers with 6 slots (12 circuits). See below pictures.



My plan is to use a Dermal tool to cut out a small section of each bus bar so that my panel is configured the same as the PD55K005. I will then run 8ga 4conductor cable from the inverter to the second main breaker and reconfigure the breaker layout per the below diagram.
The current main breaker is a 50A.



Pros:
- All breakers remain easily accessible from the camper interior, in the original location
- Removes the AC units and fireplace from the inverter OUT1 load bank
- Minimal cost: a few breakers and some 8ga wire
- Level loading across L1 and L2

Cons:
- May require a new breaker panel is I muck it up

Any feedback on main breaker sizing? Cable size? Load balancing?
Any thoughts on my plan welcomed.

[traveldawg]

Gosh - taking a dremmel tool to a breaker box. I suppose you can do that. But how do you get new feeds into the section you separate from the original buss bars?

I had that PD55K005 box in a motorhome and it worked well. If it is same size as the t then I would think that is a better solution.

Or do what I did - just put in a sub panel. Sure, it might not be inside (I put mine in my main storage bay). But it might be a better solution.

[dryfly]

I'm with Larry on this. Sure seems like a sub panel would be easier to build and maintain, and opens the possibilities of additional circuits if needed later. That is, unless there is a reasons all breakers need to be together. How often do you even need to get to the breakers?

[huntindog]

I am not an electrical engineer. I have done my fair share of electrical work, but never modify anything like a breakerbox. I figure that those types of thing are the way they are for a reason. So I leave it to the engineers.l

[acoleman43]

I'm not an electrician either, so take this with a grain of salt.

For your intended use I think you might need a sub panel. I don't think you want to share a neutral bus with both "legs". A real electrician can correct me if I'm wrong.

The main distribution panel shares a neutral because it has one input from shore power (or an inverter). The 2 legs are for a split phase system meaning you will have a 4 wire cable with 2 hot (black and red), one neutral (white) and one ground (bare). One hot goes to one leg and the other hot goes to the other leg. Both legs share the neutral and ground. Wire size is based on max amps for one leg (other leg doesn't add additional load to the neutral, it basically takes load from the neutral). So a 50 amp split phase system means you will size for 50 amps and 120V.

Load balancing/leveling applies to a split phase system, which you are not doing. You are creating 2 separate circuits. so load balancing/leveling doesn't really apply to you (besides load balancing in a split phase system is nice, but really not necessary if the cable is sized correctly). Just make sure each leg has enough juice for what you wire to that leg. 50 amps should be sufficient.

Breaker should be sized for the max current on that circuit. If it's a 50 amp system, the main breaker should be 50 amps.

cable size is determined by length of cable. Assuming it will be 50 amps and 120V a 10/2 cable can go up to 45' with 2% voltage drop....so that's what you're probably looking at (for cable from inverter out2 to sub panel).

Also I don't know how much boondocking you do, but having AC and other high current consuming devices on a circuit that is only activated when plugged into shore power really limits your comfort when boondocking

[Casa_Woody]

#acolman43
Thanks for the input. Agree with what you are stating. The reason to split the AC units off inverter power is so batteries are not drained rapidily during a outage. It's a double edged sword. Need to keep the AC's running while away from the camper as we have pets. But if the power goes out, the AC's will be off until power is restored (I'm working on a temp senor with email notiications). With current battery capacity and solar, I believe I could only run the AC's for about 2.5 hours. If home during an outage, a generator would need to be started to run the AC's.

[Soundsailor]

With current battery capacity and solar, I believe I could only run the AC's for about 2.5 hours.

Running the A/C on battery sucks a lot of battery. You may get the 2.5 hours if the solar is helping. I recently tested running my A/C on battery, and the draw from my 3,000-watt inverter was 125 Amps. With 400 Ah of storage, you'd be OK if they were fully charged when the A/C started, but the margin is pretty thin.

[Butcher]

I recently tested running my A/C on battery, and the draw from my 3,000-watt inverter was 125 Amps.

I would concur with this. I too used around 125A, A/C on, average amount of lights on, and measured using a shunt at the battery ground.

[acoleman43]

#acolman43
Thanks for the input. Agree with what you are stating. The reason to split the AC units off inverter power is so batteries are not drained rapidily during a outage. It's a double edged sword. Need to keep the AC's running while away from the camper as we have pets. But if the power goes out, the AC's will be off until power is restored (I'm working on a temp senor with email notiications). With current battery capacity and solar, I believe I could only run the AC's for about 2.5 hours. If home during an outage, a generator would need to be started to run the AC's.

Lol, yes I get it.

About a year ago I finally had enough of the 2 way (AC/propane) fridge. inefficient, small, wind would blow out flame when using porpane....I removed and replaced with a DC compressor fridge. At the time we had 2 AGM batteries and the factory 300W solar panel. First time out with the new fridge my wife forgot to plug into shore power. By about 10 PM the new fridge was beeping and flashing error code E3. I had no idea what E3 meant. Looked it up and turned out it was a "voltage out of range" error meaning voltage was either too low or too high. Huh??

Everything in the trailer was working so what could it be....well, I tried the microwave and then it hit me. No AC power. We weren't plugged into shore power and the batteries voltage had dropped below acceptable voltage for the fridge.

So I upgraded to 1200W, 800AH of batteries and a multiplus to power the entire trailer. Even with 10K+ KWH of energy we can only manage about 7 hours of air conditioner before all batteries are dead.

Bottom line is, I think it's about being aware of energy usage/consumption and managing it properly....obviously something I'm still working on

[ItchinToGo!]

I think you had better look at the instructions on that inverter again. The Victron MultiPlus-II 2x120V Inverter/Charger provides power to both L1 & L2 when inverting. I just installed this inverter a couple of months ago and this is how it is working for me. If you don't want to use certain loads while on battery power, don't turn them on. This inverter also does load sharing when not connected to a 50 amp source.