CharlesK: Interesting project you have there. I'm considering something similar myself, since I have the opportunity to get an older RV from a good friend. I do want to make a comment or two on inverter mini splits. I'm not that familiar with LG, but am very familiar with Daikin, Fujitsu and Mitsubishi. Most of the units I've worked with have a significant efficiency advantage for the 1 to one units. In other words, not a multi-head compressor. The last project I did the 1 to one units were all above 33 seer, and the multi-head were around 21-26 seer. I don't know if this is the route you are taking, but I've also read other posts where people were considering more than 1 unit. Two compressors takes up more space, but many of the multi-head compressors are much larger. Don't know about fitting one in your space.
It does make a difference if you oversize them too. Efficiency drops rapidly. I'd personally go with 2 smaller units, and run both of them. I've stayed away from ceiling cassettes, because of servicing. Some of them are horrid. There are also wall mounted cassettes, but have never used one.
I see you plan to insulate your coach. Good idea...do as much as you can, you won't regret it. I also second your process to get rid of all the propane stuff.
I missed why you decided to go with 48v. If so, do you need (2) 5k units? Could you use (2) 3k?
Just asking, because your decision process interests me.
Good luck with your project!
The minisplits and new Victron equipment have not yet been purchased. I am currently working on the interior remodel such as upgrading plumbing, wiring, cabinetry, flooring, insulation, etc. I am staying with 12VDC and 110VAC for the coach interior. Therefore, the choice of a 24VDC vs. a 48VDC battery bank is a separate issue. I am pretty well set on 48VDC at this point in time.
Meanwhile, comments and suggestions are welcome.
Given that, thank you for your comments. Let me address your questions.
1) Mini-splits: I have not yet made a final decision on the sizings. I have settled on LG because the outdoor unit will fit in the former propane tank basement compartment. This compartment is already open on the back and bottom, so there will be plenty of air flow. If needed, I can modify the compartment door for additional air flow. Overall in the coach, there is reasonable room for one outdoor unit. Having two outdoor units is problematic for both space and locations.
Why LG? The outdoor unit fits in the basement. Some of the other brands would mean an extremely tight fit, if at all. The basement height is not that great in this particular coach.
Indoor Units: The coach is physically divided into two areas: the back bedroom and the front area (seating, galley, table, cockpit). There is a self-enclosed bathroom in the middle off of a side hallway. The plan is to install one wall unit over the cockpit (above front windshield) facing aft. And, install one wall unit at the very rear of the coach, over the bed, facing forward. The bathroom would be cooled when occupied by running the ceiling exhaust fan. This will pull cool air from the rest of the coach. For cold weather, the plan includes radiant floor heating including the bathroom. This is in addition to the heat capabilities of a mini-split.
My current thoughts are to install a 7K wall unit in the bedroom and a 12K or 15K wall unit up front. The outdoor unit could be either an 18K or a 24K unit. Any of the combinations I mentioned are supported according to the LG specifications of combinations for both heat and cool. From what I understand the 18K outdoor unit would be more efficient than the 24K because it would not be turning completely on and off as much.
The SEER rating for the LG 18K outdoor unit is 22. The SEER rating for the LG 24K outdoor unit is 20.3. Neither is as efficient as 33 SEER, of course. But they do support two (or more) indoor units with a single outdoor unit.
However, if I install a 15K indoor unit up front and it turns out to be inadequate for cooling, I can only upgrade the 15K to 24K if the outdoor unit is 24K according to LG. Hmm...
2) Inverter Sizing: I decided on two 5KVA units because of my Energy Audit. I included that in my first post in this thread. I have made some adjustments along the way that persuaded me to use 5K instead of 3K. The extra margin affords me some peace of mind knowing that I will have the extra power available if needed.
Once the 5KVA decision was made, the Victron Multiplus units were out of the equation. The largest is 3KVA. That led to two Quattro 5KVA units.
I also decided to use two Victron inverter/chargers. Doing so means that everything works identically with a) 50A (120/240VAC) shore power, b) he on-board 8KW(120/240VAC) diesel generator, or c) two 120VAC inverters configured in split-phase providing 120/240VAC at all times.
3) 24V vs. 48V.
My DIY battery will consist of 32 3.2VDC cells. If I configure them as four 24V batteries, I will need four BMS units. If I configure them as two 48V batteries, I will only need two BMS units. That saves a couple of hundred dollars.
Each Quattro 48V5KVA units currently sells for $283.05 less than the Quattro 24VKVA units. For two Quattros, that is a $566.10 savings to use the 48V units.
Additionally, there are some technical reasons that others have mentioned that also indicate 48V is a better choice for this particular project. Some may be listed here. Some from another forum I frequent.
Again, thanks for your comments.