Request: Review of Proposed 28KWh / 3KW Solar / 24V/5KW inverter RV system

CharlesK

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Jan 31, 2021
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Location
NE Florida
Background

I have a 1991 American Eagle Diesel Pusher RV. This is a Class A motorhome built on a Spartan chassis with a Cummins 8.3L 6CTA Mechanical Engine and an Allison MT643 4-speed automatic transmission. At only 90K miles on the chassis, I hope that it will be around for a while.

The goal is to update the coach to a comfortable, self-sufficient vehicle that will serve us as my spouse and I travel around the country.


Conversion to All-Electric

As part of the upgrades, the decision was made to convert to an all-electric vehicle. Well, in the RV motorhome world that means eliminating the propane systems. Sometimes that means using diesel fuel for a hydronic heating system. We decided to not go that route and only use the diesel for powering the main engine. Everything else would rely on electric power.

All of the propane systems on-board have been removed. There no longer is a propane storage tank on-board. That means the original water heater, fridge, furnaces, and stove/oven all will be replaced.

There is an on-board diesel generator. But it a) makes noise, and b) uses fuel. So, adding solar power was added to the upgrades. It is quiet, and the sun is usually available on a daily basis. If not, the generator is still available as a reliable backup.

There are many upgrades in the works. New cabinetry, seating, entertainment systems, communication systems, upgraded plumbing, etc. For the purposes of this discussion I am only concerned with the electrical upgrades. Actually, the electrical "upgrade" is more of a complete replacement for a large part of the electrical project rather than an upgrade.

The original on-board house electrical consisted of a 2000W MSW inverter, a 75A 12VDC converter, a 3-input Automatic Transfer Switch, a 50A shore power connection, a 8KW Onan 120V diesel generator, a distribution panel for 120V and 12VDC, and a few other connection/switch boxes that I still cannot identify. From what I can tell, I believe some of the extras have been wired/rewired after the original purchase. The house battery system was 4 12V flooded lead acid batteries.

For the most part, the items in the previous paragraph will be removed. The diesel generator will stay.

The Plan

Skipping a lot of the reasons why, here is a short list of the new on-board electrical appliances and systems.

Residential electric refrigerator
Dual-zone mini-split for heating/cooling (one wall unit in front, one in bedroom)
Radiant Floor Heating (in case we visit the relatives in the cold of January, expected unusual low temps of 20F)
Induction Cooktop
Microwave/Convection Oven
Electric Water Heater
TVs, laptops, LED lighting, Cellphones, Washer/Dryer, Cooking Appliances

Using the resources I found on this forum, I completed an Energy Audit.

Thanks to all who helped create this resource. (y)

Based on the results, I have designed a house electrical system that I believe will make the coach energy-independent. Unless we get really crazy with energy usage, we should never need shore power, and only need to use our generator as a back-up system in case of prolonged bad weather.



Here are the results of the Energy Audit Spreadsheet.

System size calculations
Full Load W-hrs.​
10776.5​
W-Hrs.​
Full Load Watts​
3834​
Watts​
AC Watts​
3709​
Watts​
AC Surge wattage​
1020​
Watts​
AC Watt-Hrs​
10418.5​
W-Hrs.​
DC Watts​
125​
Watts​
DC Watt-Hrs​
358​
W-Hrs.​
Inverter Sizing​
Inverter efficiency​
94.00%​
%​
Min continuous Inverter size​
3946​
Watts​
Min Surge Inverter size (Input Watts)​
5031​
Watts​
Battery Sizing​
Daily Storage Requirement​
11442​
W-Hrs/Day​
Max discharge from full CHARGE​
90.0%​
%​
# days of storage capacity​
1.0​
Days​
System Voltage​
24.0​
Volts​
min Battery capacity W-Hrs​
12712.8​
W-Hrs.​
min Battery capacity A-Hrs​
529.7​
Amp Hours​
Max continuous current to DC Loads​
5.2​
Max continuous DC current to Inverter​
164.4​
Max continuous current from bat.​
169.6​
Amps​
Max Continuous discharge rate​
0.32​
C​
Solar Array Sizing​
# sunny days to recharge while under load​
3.0​
Days​
Required Total daily Solar output (Sunny)​
15255.3​
W-Hrs.​
Insolation # (Equivelent hours of full sun)​
5.0​
Hours​
Min Solar Cell Wattage​
3051.1
Watts​
Max Charge Current​
127.1​
Amps​


The concepts

Energy independence. Depending on where we are parked, or if we are driving, I want to have a fully-functional coach. That means shore power may or may not exist, 120VAC or 240VAC may or may not be available, etc.

Based on the Energy Audit, I have determined that a 5000VA inverter will supply the AC needs. A 24V system was selected to reduce the wiring sizes, and less BMS's than a 12V system. I decided against a 48V system because of the perceived dangers. This may or may not be real, but a 48V system vs 24V may not have that much advantage anyways. A Victron Quattro eliminates the need for a separate automatic transfer switch, as it has its own internal transfer switch.

The Audit also suggests about 3KW of solar. That should fit on the 38' roof. There is about 30' of actual roof (subtracting the front and rear caps) after a number of unwanted skylights and vents, and the two roof-top Air Conditioners are removed.

I added a 12V battery to supply the RV 12VDC loads for two reasons. First, in case of a surge requirement that the Buck Converter may not be able to handle. Second, if the Buck Converter fails, we can still operate the essential 12V Loads.

I included an autotransformer. The most pressing requirement is the 240VAC dual-zone mini-split. The autotransformer will provide both 120VAC and 240VAC. It also provides load-balancing for its 120VAC outputs.

The autotransformer concept is based on a schematic found on Victron's website: https://www.victronenergy.com/uploa...-phase-120V-to-120-240V-with-Quattro-120V.pdf


The Proposed Electrical System

Already Purchased equipment:

Progressive Industries EMS-HW50C Electrical Management System (Hardwired installed. Shore power cord feeds directly into this.)
LiFePO4 battery technology (4 sets of 8s 3.2V 272Ah cells. Cells are on order from @Michael B Caro) (Four 8s Overkill BMS - Ordered and received.)
Victron BMV-712 Shunt

Proposed Purchases:
Victron Quattro 24/5000/120 Inverter/Charger
Victron 100A Autotransformer
Busbars (possibly Victron Lynx system)
100A 120/240VAC Breaker Box
~3KW roof-mounted solar panels
Victron Solar Charge Controller(s)
Victron CERBO GX
Victron GX Touch 50
Victron DC 24V-12V Buck Converter(s)
12V Battery
Various cables/fuses/switches/etc.

There are lots of details NOT INCLUDED at this point. Before I dive into the necessary details, I want to be certain that my overall design is sound. Just like planning a trip/vacation, there is no sense trying to determine what roads to take until one knows where they are going. :rolleyes:


American Eagle Diesel Pusher V0.2


1622916757922.png



Comments, suggestions, questions, etc. are welcome.

I have learned a lot about DIY Solar and more since I joined this forum. I appreciate the sharing of knowledge and hope to be able to contribute a small part of what I have learned sometime in the future. But, right now, I am still climbing the learning curve and need to learn a lot more before I feel that I can safely contribute.


Thanks!!! :)

Charles
 

apcorob

Solar Enthusiast
Joined
Mar 1, 2021
Messages
33
Charles, I am planning the nearly identical system, probably 3 months behind you. I can't wait to see what the experts here say.....and then to watch what you do.

Right now I have decided to focus on 24 volt roof mounted air conditioners because I am not yet comfortable with a 240 volt mini split (120 somehow is comfortable!); and, the mechanical issues of a multizone system with a single compressor. I also think you should look at the victron ez solar instead of the quattro....it is coming to the usa soon. Available now in Europe.

I am anxiously watching with great curiosity.

After watching a horrible propane accident I agree with your decision.

I also hope you have more battery than you need!

Pictures please
 

Bob B

Photon Sorcerer
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Sep 21, 2019
Messages
3,309
Have you seen @cinergi 's build?

 

CharlesK

New Member
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Jan 31, 2021
Messages
25
Location
NE Florida
Charles, I am planning the nearly identical system, probably 3 months behind you. I can't wait to see what the experts here say.....and then to watch what you do.

Right now I have decided to focus on 24 volt roof mounted air conditioners because I am not yet comfortable with a 240 volt mini split (120 somehow is comfortable!); and, the mechanical issues of a multizone system with a single compressor. I also think you should look at the victron ez solar instead of the quattro....it is coming to the usa soon. Available now in Europe.

I am anxiously watching with great curiosity.

After watching a horrible propane accident I agree with your decision.

I also hope you have more battery than you need!
Here are my thoughts about choosing a minisplit over roof units.

About a year ago or so, I had replaced one of the two original air conditioners with a new Coleman 15KBTU heatpump. The original was a non-ducted unit and very noisy. The new unit was also non-ducted and almost as noisy. I was not impressed. I was hoping for better.

I was in the process of adding a ductwork system to reduce the noise. The ductwork was partially completed, but still very noisy. The compressor on the roof runs at full noise level regardless of the inside unit fan speed. Then, last summer, I visited someone who had just installed a 24K BTU minisplit. It was running at full power and I could barely hear the inside unit. The outside unit was a bit louder, but sooooo much quieter than my brand new roof unit. I visited this person again last week and the minisplit was even quieter than I remembered.

Also, a minisplit can provide heating down to much lower outdoor temperatures than a heatpump. Since I removed the gas furnaces, heating the coach is a requirement. The units I am selecting will provide heat to -4F outdoor temperatures. There are some that can work at even lower temps. I don't plan to be in any place that cold though. LOL

After some thought and measuring I determined that I could mount the outside unit in the basement bay where the propane tank was located. That compartment already has an open floor and open back. That may be enough ventilation. If not, I can modify the bay door. I am planning on two indoor wall units. The only issue was having 240VAC with or without 50A shore power. An autotransformer will solve that issue. I did consider two 120VAC minisplits, but that would require two outdoor units. I do not want to give up any more room in the basement.

Removing the two roof units will make room for more solar panels. Not only is there more room, there will not be any shadows from the former roof units over the solar panels.

You probably have already found @cinergi 's RV system. Take a look at his recent youtube videos since he got his 5th wheel. The power usage of the minisplits is much lower than a traditional roof top unit. I don't know how that compares to the 24V roof units you have found though.

May I suggest that you find someone who has a minisplit installed and experience it first hand? It could be an RV (very few out there right now) or a building.


Regarding propane safety, many years ago I watched the house across the street from me explode from an underground natural gas leak in our neighborhood. The gas company tech was in the basement across the street when he asked the homeowner, who was at the top of the stairs, to turn on the light switch. I watched a 2' blue flame surround the base of the house outside from my kitchen window. Fortunately they both survived. I am not a fan of gas.

I will look into the EZ solar, thank you.
 

cinergi

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I'll be posting more numbers soon as we're about to have 2 days over 90F ... but some notes:
* I can generate about 20kWh with 3.3kW of flat panels
* I use around 15kWh/day when I'm running the A/C
* Running a mini-split for heat consumes a LOT More power than cooling, and during a time when you get less sun. I would not have survived completely off-grid were it not for my propane heat
* I went with propane for range to avoid using electric. Depending on how much you cook, this could be more of a factor than you think
 

cinergi

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Are you sure about your max draw? Microwave, mini-split, hot water heater, and heated floors would put you over. And that doesn't include the cooktop, fridge, toaster, etc.
My max draw so far has been 4.5kW (AC) - rare but happens. More typical peak is 3kW. And I'm propane ... I'm worried your inverter is undersized. I'm also worried about the use of the A/T. I would use the A/T just for the mini-split and drive the other 120 loads from the inverter directly so that you don't have problems balancing the neutral line.
 

CharlesK

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NE Florida
I'll be posting more numbers soon as we're about to have 2 days over 90F ... but some notes:
* I can generate about 20kWh with 3.3kW of flat panels
* I use around 15kWh/day when I'm running the A/C
* Running a mini-split for heat consumes a LOT More power than cooling, and during a time when you get less sun. I would not have survived completely off-grid were it not for my propane heat
* I went with propane for range to avoid using electric. Depending on how much you cook, this could be more of a factor than you think
If I may, I have a few questions.
First, thank you for the VRM portal. The information is very helpful.

IIRC, you have a 24K mini-split with two indoor units. What are the sizes of the indoor units?

I am looking at LG mini-splits in various sizes. I know there are other brands, but the dimensions of the LG outdoor unit work well with the former propane tank bay. I am after two indoor units: one above the cockpit and one above the queen bed. My coach has a side hallway, so air cannot travel a straight path to the rear bedroom.

I did note the 90F+ temps yesterday and today in your area of the country. I am wondering what other appliances were operating besides the mini-splits these two days. I will wait until you post your analysis, but the VRM data looks very good. Having the battery topped off by noon, even with 90F temps, has to feel good.

I am revisiting my Energy Audit data and Quattro selection. The advice about where to place the autotransformer (AT) is not lost on me. Your idea was in my first design (V0.1 was not published here). I thought that would be a better way to go. However, the AT also is supposed to provide load balancing across the two 120VAC legs. That is why I changed it for V0.2. More research needed!

I am impressed with the Panasonic panels. They seem to start working very early in the day; not waiting for the sun to get very high to produce power. It appears that power production starts about an hour after sunrise; starts to increase about an hour later, and is producing quite well by 9:00 AM. I started to wonder about the abrupt drop-off in solar production in the early afternoon. Then, I realized that your batteries were full. :) Again, the VRM data is very helpful.
 

cinergi

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If I may, I have a few questions.
First, thank you for the VRM portal. The information is very helpful.

IIRC, you have a 24K mini-split with two indoor units. What are the sizes of the indoor units?

I am looking at LG mini-splits in various sizes. I know there are other brands, but the dimensions of the LG outdoor unit work well with the former propane tank bay. I am after two indoor units: one above the cockpit and one above the queen bed. My coach has a side hallway, so air cannot travel a straight path to the rear bedroom.

I did note the 90F+ temps yesterday and today in your area of the country. I am wondering what other appliances were operating besides the mini-splits these two days. I will wait until you post your analysis, but the VRM data looks very good. Having the battery topped off by noon, even with 90F temps, has to feel good.

I am revisiting my Energy Audit data and Quattro selection. The advice about where to place the autotransformer (AT) is not lost on me. Your idea was in my first design (V0.1 was not published here). I thought that would be a better way to go. However, the AT also is supposed to provide load balancing across the two 120VAC legs. That is why I changed it for V0.2. More research needed!

I am impressed with the Panasonic panels. They seem to start working very early in the day; not waiting for the sun to get very high to produce power. It appears that power production starts about an hour after sunrise; starts to increase about an hour later, and is producing quite well by 9:00 AM. I started to wonder about the abrupt drop-off in solar production in the early afternoon. Then, I realized that your batteries were full. :) Again, the VRM data is very helpful.

My ODU is 30k and I have two 9k IDU's (I will upgrade one of them to 11k).

Today with 90F degrees, my LR crept to 74 degrees (set to 64 / max fan) - so that's why I'm upgrading to 11k IDU there. My power usage (AC side only) was 15kWh. Add another 2-3 for DC usage for a total of about 17kWh. My battery hit full both yesterday and today by 1pm so I was "throwing away" solar for several hours today, despite the AC's running pretty hard. 14kWh power so far today (2 more hours to go).

There's no point in load balancing 120 legs in your setup as you only have 1 leg (1 inverter).

Yeah I'm very happy with these panels! Glad my graphs are useful!

BTW I'm running/living full time without compromise inside.. so the fridge is running.. today I cooked on the stove (= heat that the AC had to remove), TV, computer, lights, coffee, etc ...
 

CharlesK

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NE Florida
@cinergi : Thanks for the note about not needing balancing on a single 120VAC leg. The Datasheet for the Victron Autotransformer (AT) includes a diagram for load balancing stacked inverters. Clearly my diagram has only one inverter, so it is not stacked. :rolleyes: I made the change. The appropriate datasheet diagram I need to use is for a Step-Up.

Also, moving the AT after the Breaker Box instead of before, and only supplying the mini-split with the AT, means I can use a smaller AT. I only need a single 20A breaker with 240VAC. And, the mini-split installation manual only requires a Ground, Neutral, and HOT. So, I do not need split-phase either. Although the same AT can provide split if I need it in the future for a different purpose.

I am still working on deciding what size mini-split ODU and IDU's I want. I am a bit surprised that they installed two 9K IDU's in your 5th Wheel with a 30K ODU. I was thinking of a 7K or 9K unit in my back bedroom, and a 12K unit up front with an 18K ODU. Based on feedback from you, and others, I may want to increase the front unit. That big front windshield will definitely let in a lot of sun/heat. My original thought was for an 18K ODU, but maybe I should get a 24K ODU. The insulation on my 1991 coach is probably less than your new RV, so I may need more cooling/heating capabilities. However, the cubic footage is much less. I have a lower ceiling and no slides. I am adding a layer of 1/2" foam insulation board on the exterior walls and ceiling during the remodel that should increase the R-value. Covering the roof with panels should help with the direct sun-load.


I am reviewing my Energy Audit. I am still comfortable with the Quattro 24/5000 with 4000W output. I do have the diesel generator onboard. If I understand it correctly, the Quattro will allow for 50 or 100A of pass-through from the generator (or shore power). I am assuming that it is only 50A if I am only feeding one 120VAC leg into the Quattro. That is 6000W of power with external hookups, and 4000W (10000W Peak) from batteries alone.


24V vs. 48V. For my plan, having a 24V battery system would mean four sets of 8s 3.2V cells. A 48V battery system would mean two sets of 16s 3.2V cells. I hear things about how a 24V system is safer than a 48V system, and that nothing higher than 24V should be used in a mobile application. But, folks are using 48V successfully in RV's. Am I being paranoid? The house electrical systems (lights, water pump, etc.) will remain 12VDC in any case.

QUESTION: Are there any advantages/disadvantages/warnings of using a 48V system instead of a 24V system in a motorhome?



Here is block diagram V0.3.
1623174653692.png
 

cinergi

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For LG, the recommended IDU configuration is between 40% and 133% of the ODU - so I'm well within the recommendations at 18k out of 30k. 18k for your front area is probably enough and if it's not, consider getting something like a Magnashade for the *outside* of the windshield to prevent the heat from getting inside the glass in the first place.
48 vs 24 ... i don't think there's a safety issue to consider especially because you're not actually running 48v throughout the motorhome, just to the inverter. I'm running 48v (single battery, 2p16s) in my setup. Works great. There are pro's for the SCC's (usually a smaller/cheaper one works because the amperage is lower, smaller gauge wiring, ...) ... can be some mild cons from a price perspective (battery switches that handle the voltage, DC-DC converter pricing and available amperage, etc). But that's all working great for me.
 

CharlesK

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NE Florida
Update:

Since my last post, I found that I made an error while evaluating my existing on-board generator. When I tested the voltage output (at the breaker panel at the foot of the bed in very cramped quarters) I found 120VAC between each leg and neutral. I also found 0VAC between the two legs. I thought the probes were touching the exact same spots on the terminals. My determination was that there was NO split-phase output from the generator.

Evidently the probes on my tester did not reach the terminals properly. Something told me to try again a few weeks later. This time, lying flat on my stomach in the hallway outside the bedroom, I accessed the AC breaker panel again. This time I found 240VAC between the two legs. I tested with the generator. I tested again with shore power. Both gave me 240VAC. And, I still found 120VAC between each leg and neutral. Much better test results! That tells me that I do have split-phase 240VAC.

I guess I had heard and read from so many forum posts over the years that 240VAC in RV's was NOT NORMAL so, when I found 0VAC the first time, I accepted the initial results. (n)

So, this changes my previous plans a lot!

Here is a new schematic (V0.5) that accepts a) 240VAC split-phase from the generator, and b) 240VAC 50A, 120V/30A, or 120V/15A from shore power.

To have 240VAC split-phase available at ALL TIMES (shore power, generator, or inverter only), using Victron equipment, this new plan will require two inverter/chargers instead of one.

1626654372944.png



Note that the schematic calls for two (2) MultiPlus 24/3000 units. This should supply 4800W of AC power. I am still debating if this is enough to power everything that I plan on running at once. Yes, I have completed an Energy Audit spreadsheet that I found on this forum. It is telling me that 4800W might be enough depending on what is running concurrently. The next step up would be two (2) Quattro 24/5000 which would supply 8000W continuously. More things could run simultaneously. But, do I really need to run the dishwasher, washer/dryer, mini-splits, and cook all at the same time?

Also, with the Quattro units I would have the option to switch to two (2) Quattro 48/5000 units and reconfigure the DIY Battery Bank to 48V (2 sets of 16S 3.2v 272Ah cells). I already have in hand four 8S (24V) Overkill BMS units (still in the original boxes). However, changing to 48V would mean a reduced cost for the Quattro's and smaller gauge wiring. The reduced Quattro cost alone would more than offset purchasing two 16S (48V) BMS units.

I am following the @cinergi mini-split upgrade. His generosity in sharing his results is very helpful in sizing my future mini-split system. Thanks!

Once I determine the mini-split power requirements, I should be able to select the inverter/chargers. Then I need to size fuses, breakers, wiring, panels, etc.

Is there a recommended resource for calculating the sizing of parts? I did have some E.E. training back in college. But it has been a few years. Anyone else learn computer programming with Hollerith cards? :rolleyes:
 

2009Bounder2020

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Dec 28, 2020
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104
Have you figured in the current draw of your auto leveling system. Mine is 12 volt and pulls over 200amps.
 

HarryN

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Jul 25, 2021
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You are correct - the victron 3000 is really a 2400 watt inverter, similar to how a honda 3000 is really a 2400 watt generator. At least that is what my testing is showing.

The 5000 is a great inverter and it is a lot easier to wire in 48 volt than 24, but you are right that it is less common.

Blue sea and some others have on-line calculators that can size your wires for you. Just enter the estimated round trip distance and it will spit out a suggestion.
 

CharlesK

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NE Florida
Have you figured in the current draw of your auto leveling system. Mine is 12 volt and pulls over 200amps.
Good question. So, I did a bit of experimenting today.

My motorhome has two separate electrical systems. They are labeled CHASSIS and COACH.

There are two switches inside the coach (hidden inside an upper cabinet). I believe some folks call these "Salesman Switches." Each controls a relay: One for the CHASSIS. One for the COACH (house).

The only way I can get the leveling system to turn ON is if a) the CHASSIS system is ON and b) the IGNITION is in the ON POSITION.

If the COACH electrical system is either ON or OFF, and the CHASSIS system is ON and the IGNITION is ON, the leveling system works.

That would lead me to believe that the leveling system is not dependent on the COACH (house) system. Therefore it is not a consideration for my COACH electrical plan.
 

HarryN

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Jul 25, 2021
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Interestingly, there is a similar thread related to using 24 volts and how to deal with leveling:

 

CharlesK

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NE Florida
Interestingly, there is a similar thread related to using 24 volts and how to deal with leveling:

Thanks for the link.
In my case, the leveling system is powered by the chassis batteries with the ignition on. Evidently some other motorhomes do it differently. I never gave it much thought.

Also, my motorhome does not have slides (another power hungry use). I have also eliminated the 12V RV fridge, the propane furnaces, the propane water heater, and every incandescent and fluorescent light that I could find. This reduces the demand on the 12VDC house system quite drastically.

Still, I am planning on a 12V battery after the DC-DC converter to supply the 12V house loads. This will handle any surges and higher transient currents. Furthermore, if the DC-DC converter should suddenly die, I will still have basic 12V house power. Or, at least until that battery dies. The point is I won't be instantly left in the dark.
 

CharlesK

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Jan 31, 2021
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NE Florida
OK. I am now on version V0.6. :)

Thanks to everyone who has commented. A lot of thought and additional analysis based on your input resulted in changes.

The big change is having a 48V battery bank. I am not certain of the internal configuration yet that I want to use, but it will be comprised of 32 3.2V 272Ah LiFePO4 cells and the appropriate BMS units. Switching to 48V means different Inverter/Chargers, a different DC-DC charger, etc.

One of the key points, not readily apparent in this block diagram, is that all AC circuits will be available regardless of Generator and/or shore power connections. The Victron Quattro does have the ability to have "switched" circuits; a second AC output that only work when the genny or shore power are connected. I am NOT using that capability. All AC circuits will always be available.

I am still working on the solar panel configuration. There are numerous other threads on this forum that are very helpful. For now, my thoughts are to cover the motorhome roof with as much wattage that will fit and still leave space for the necessities (TV antenna, radio antenna, exhaust vents, shower skylight). The roof membrane will be replaced after the roof air-conditioning units are removed. So,solar panel selection is being delayed.

1628016587328.png
 

eXodus

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Jul 27, 2020
Messages
623
am still working on deciding what size mini-split ODU and IDU's I want. I am a bit surprised that they installed two 9K IDU's in your 5th Wheel with a 30K ODU. I was thinking of a 7K or 9K unit in my back bedroom, and a 12K unit up front with an 18K ODU. Based on feedback from you, and others, I may want to increase the front unit. That big front windshield will definitely let in a lot of sun/heat. My original thought was for an 18K ODU, but maybe I should get a 24K ODU. The insulation on my 1991 coach is probably less than your new RV, so I may need more cooling/heating capabilities. However, the cubic footage is much less. I have a lower ceiling and no slides. I am adding a layer of 1/2" foam insulation board on the exterior walls and ceiling during the remodel that should increase the R-value. Covering the roof with panels should help with the direct sun-load.
I also got an Class - yeah that windshield lets in a ton of heat.

Yet, you can not compare the BTU of a Minisplit (Inverter) with those of the Roof Top A/C Units. (Or in general A/C Units)

I don't know why, (maybe the measuring cycle for determining "BTU" is garbage)

A Inverter A/C unit. (Minisplit or other) Delivers more real world BTU then a other type of A/C system of the same nominal size.
I've replaced a 3 ton (36000 BTU) single stage in a home with a 8000 and 12000 BTU Inverter unit - and those things cool better.
Went down by 16.000 BTU and still got more cooling.

Yet, the good thing is - with Inverter units you don't have to be as careful with sizing. So go ahead put in a large Mini Split :p
 

cinergi

1.21 Jigawatts
Joined
Aug 9, 2020
Messages
1,157
Ducting is the biggest killer of A/C, especially in an RV.

One thing I learned just yesterday -- with the sun setting on the side where I have awnings, I can keep the temp inside at 68 (88 outside) all day. When it sets on the other side w/out awnings, the temp crept up to 76. So fixing heat intrusion is super, super important. I have awnings still due to be installed on the other side... and I'll be tinting my windows.

My mini-split had insufficient refrigerant ... once that was fixed, I am holding a 20-23 degree temp split. 9k BR and 12k LR cassettes. 38' 5th wheel. Well-insulated (minus the windows).
 

CharlesK

New Member
Joined
Jan 31, 2021
Messages
25
Location
NE Florida
Ducting is the biggest killer of A/C, especially in an RV.

One thing I learned just yesterday -- with the sun setting on the side where I have awnings, I can keep the temp inside at 68 (88 outside) all day. When it sets on the other side w/out awnings, the temp crept up to 76. So fixing heat intrusion is super, super important. I have awnings still due to be installed on the other side... and I'll be tinting my windows.

My mini-split had insufficient refrigerant ... once that was fixed, I am holding a 20-23 degree temp split. 9k BR and 12k LR cassettes. 38' 5th wheel. Well-insulated (minus the windows).
I am still in the design phase for my remodel. have four questions for you, please:

1) Double-checking my design, I have two Quattro's together supplying 240VAC. The LG minisplit outdoor unit spec sheet says input voltage should be 208-230VAC.

I noticed on your VRM it says "120.0" and "120.2" volts. Adding that together should mean 240.2V is being supplied to the LG unit? That is over 230VAC. Is this an issue with the LG?

2) Do you have any 240VAC appliances that require 4-wire connections? That is, two hots, a neutral, and a ground?

3) Does your generator supply 120VAC or 240VAC? If only 120, does it supply both Quattro's?

4) If I have the correct schematic for your system, you are NOT using AC OUT-2 on either Quattro. Is that still correct?

I appreciate you sharing your knowledge. Thanks!!!
 
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