Advice and Counsel sought for Off grid system

DougU

So far my efforts to work with solar vendors has done little to educate me and much to shake my faith in the honesty of mankind. (No, I don't want your financing and No, I'm not interested in your rebate program. Ugh)
What I have:
16 Victron AGMs 220 Ah (intend to wire in a 48V/880Ah array 
2x Victron 250/100 Solar Charge Controllers 
Midnite Star Solar Charge Combiner
Exeltech 8kw inverter (anticipate I will soon add the other two modules to increase to 10kw.)
A pallet of shattered glass that used to be 20 400watt solar panels (shipping industry is a train wreck these days)
15KW propane generator to serve as backup and for high demand shop loads (welder, air compressor, etc.)

Use case is an off-grid farmstead in the Florida Panhandle. 1200 sf barndominium with two residents.  Estimated 13KwH daily consumption.  LP water heater, clothes dryer, stove and generator.  220v loads include well pump, small demand water heater for one sink, and occasional use welder and air compressor.   Wood heat with 3 minisplits (each runs on a 220v 15a circuit) that are rarely if ever used simultaneously. Planning to do a roof mount solar install. I have two unobstructed south-facing roof sections available for install: 14x30 feet at 2:12 pitch and 10x30 at 3:12.  Roof is 5v crimp metal.

Goal is self reliance and reliability.  Component level R&R (no integrated, all-in-one "solutions")

Questions:
1.The Exeltech does not have an automatic switching function (don't want one, want to have manual control) What device would you use for a Break-Before-Make connection for isolating the inverter prior to starting the generator?
2. Wiring the battery array, I am using 4/0 cables.  Assume all runs should be the same length?  Should the DC fusing be done at each bank of 4, or at a single point where all 4 banks come together?
3. Any ideas where to find a 48v battery charger in the 100a range?  Id like to be able to charge the array any time the genny is running, but all the 48v chargers I can find are in the 10-20 amp range.
4. Any ideas on a source for the panels/wiring/rooftop racking with an honest point of contact?

Photowhit

I'm likely to be able to help you out, I'm even from Tallahassee...

1) I suspect you could use any transfer switch or even an interlock that meets your specs.

2) I would never design a system with 4 separate strings of batteries in a battery bank (while array is an okay term, it's less confusing to use battery 'bank' since we use array to describe the manner of solar panel layout) Separate strings don't tend to share charging or loads very well. Might check out this site to wire with as close to equal resistance as possible;

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

3) Iota is only in that 13-20 amp range, as a stand alone charger. Might look into a inverter charger that might provide higher current. Midnite's DIY 5000 would reach 40 amps, but is a 120v unit. Might look into a Growatt or other in the 5000 watt range in a 240 volt, should get you in the 80-100 amps range.

4) Lots of people should supply racking, might need an engineer study of your roof in Florida, with new regs. Some AHJ might ignore totally off grid homes, but will your insuranse company?

DougU

Thanks for the response PhotWhit.  Based on a read from the link you shared, I would be looking at something like this:
Does that pass muster?

BB.

Typically, you would move the Red wire to the Top Right battery terminal and the Black bus wire to the bottom left terminal... That way all current paths have the same number of "jumper wires" (4 total) to the common bus connection. In your drawing above (I am slightly dyslexic--So I have to look very hard and these wiring diagrams to not make a mistake in understanding).

Your number of jumpers from from 1 to 3 and each string has a "different" wiring/path resistance. The single jumper lower resistance and will carry more current--The 3 jumper will have higher resistance and carry (on average) less current.

Another couple of issues you may want to look at... When you have parallel battery banks--You may want to have a fuse per battery string so that one shorted battery bank (wrench falls across terminals, metar battery box short, plate(s) short in one string) so that the other three strings do not feed excessive current to the shorted string. A fuse or breaker per string will help stop the short circuit(s) if any occur and reduce the chances of wires overheating/starting a fire...

Blue Sea makes some very nice/small (not cheap) compact fuses and fuse holders:

https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

You can also do this with circuit breakers (may not be much more than the fuse+holder) and this gives you the ability turn on/off strings for diagnosis and fault isolation...

In general, using a large breaker for your main battery bus disconnect is handy too... Don't have to keep a supply (of not cheap) fuses on hand, and easy to shut down for maintenance.

For your wiring... We usually assume Negative Ground of the battery bus (and all major metal things, like metal battery box, metal electrical panels, water and propane piping, RV Chassis, whatever). Then you only need fuse/breakers on the positive leads.

In your drawing, you have one fuse for the AC inverter... But you have (smaller AWG?) wiring for chargers, etc. Each "branch circuit" should have its own circuit breaker sized to the wire AWG/Current Capacity.

Two charge controllers, one AC charger--Then at least three fused/breaker branch circuits.

And as above--Using properly rated Circuit Breakers--Lets you isolate various branch circuits by flipping the breaker(s) off--And allows the rest of the system to run normally (or you can shut down whole system for winter when you are away from home, etc.).

Regarding the "solar charge combiner"... You may have just done a drawing shorthand... But, in general, you would have one array combiner box per MPPT Controller... Two MPPT controller cannot share the "same" solar array.

Some quick answers to complex questions you asked (I tend to get wordy--I will try not here):

Regarding Transfer Switches... As PhotoWit says--Lots of switches out there.. The standard issue would be to purchase AC inverter(s) that have AC1 and AC2 inputs (i.e., grid and genset) and have the inverters do the transfer as needed... You can wire up standard electrical panels with circuit breakers and either purchase sheet metal interlock kits (for true transfer switches) or use lockouts. Typically would be belt and suspender answer... The AC inverter internal auto transfer switch and manual transfer/lockouts if you need to take an AC inverter out of service for repair/replacement (i.e., bypass inverter to supply grid/genest power directly to AC loads with inverter removed).

Personally, I would like to see you get larger AH rated batteries (i.e., instead of 12 volt @ 220 AH battery, use 6 volt @ 440 AH batteries--And you are down to 2 parallel strings as an example) and aim for 1 or 2 or 3 strings. Many folks like 2 parallel strings for redundancy (one string fails, can shut off and limp along until repairs are made). More than 3 parallel strings can work fine--But you end up with more costs (wiring, connections to clean & torque if flooded cell, more cells to check water levels on, etc.).

-Bill