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shovelshort
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# Posted: 20 Jan 2012 10:24
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Quoting: MtnDon With 4.2 hours of sun you'd need PV modules that would supply a minimum of 9.25 amps at peak power. That would recharge the batteries in a day of good sun. Peak voltage should be something in the neighborhood of 17 to 18 volts when used with a standard Non-MPPT charge controller. So 17.5 x 9.25 = 160 watts of PV modules, approximately.
Ok, let's be direct then. If you were to set up a solar power "kit" for me that will give me my 160 - 200? watts, what would you suggest? I absolutely trust your knowledge and experience on what is out there and would probably buy whatever you suggest.
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ranchboss
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# Posted: 20 Jan 2012 13:29
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I have 3 harbor frieght sets = 135 watt 1 northern tool panel = 60 watts 30 amp charge controll and a aims 5000 watt inverter with 4- 85 amp hour batteries and as a rule we run all weekend and have never ran the batteries down but I run power tools off the generator we run the tv all day and night it seems like and lites at nite and I couldn't be happier I would like to get bigger pannels so I could run ac in the evening in the summer but it works well as it is. oh and I forgot my wind generator it dosn't do much in the piney wood of east texas but it works some times I would have to have a 300 ft tower to get good wind generation my property goes up a 100 ft higher behind or cabin so it would take a tall tower.
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MtnDon
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# Posted: 20 Jan 2012 17:36
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I was going to recommend a Blue Sky Energy controller, model 2512iX, an introductory level MPPT controller. $220 - 240. But i discovered a potential problem.
All controllers have an upper limit to the voltage than can be input; there are also amperage limits. The voltage limit is the bugabear. Explanation: PV modules have a Vmp rating and a Voc rating. Vmp is the maximum power voltage, what it produces while exposed to bright direct sun. Voc is open circuit voltage, the voltage peak the module may produce when the morning sun strikes the cells. This is always higher than the Vmp and occurs as a spike, a sudden power burst. On a cold winter day the Voc can spike higher than the modules rating.
The upper voltage limit on the 2512 is 36 volts. The Blue Sky folks recommend PV modules should have a Voc no higher than 28 volts to ensure the cold weather spike remains low enough to be safe.
Solar PV modules have kept getting larger and larger over the past few years. Lower prices per watt too. The difficulty is that most panels are now capable of producing higher voltages than the Blue Sky 2512 can handle. The commonly available modules have outgrown the 2512.
There are MPPT controllers that can handle the higher voltages, but they cost considerably more. Maybe twice as much. If you're looking at a small system I believe you are going to find that a lot of money for the controller.
So reflecting on all on the Sunelec kit you earmarked looks better all the time. The controller is US made too. It just doesn't make the most efficient use of the sun, but that is common among all the lower priced entry level systems.
What do you think? I'll help all I can but this may be a stumbling block.
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MtnDon
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# Posted: 20 Jan 2012 17:49
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I suppose the way to rationalize using an NON MPPT controller is to remember how much cheaper the PV modules are today as compared to a few years ago.
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MtnDon
Member
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# Posted: 20 Jan 2012 18:08
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Here's a thought. If you go with the Sunelec PV module and controller you can do without the combiner box they aren't including anyway. A combiner box is just a handy way to wire up more than one PV module. If there's no inspection you can use an off the shelf AC disconnect like this GE one. The purpose is to provide a method to "turn off" the power from the PV modules to the controller. This is a simple pull out disconnect. It is meant for AC but in this low power DC application it will work; won't pass code though.
Or this Square D QO box can be used in this case. A Square D QO circuit breaker can be fitted in this box. QO series are usable in low voltage DC circuits. For a one module system like the Sunelec it would work. Use a 15 amp QO breaker.
Solarseller.com also sells DC rated breakers that could be used, but they won't fit in that box. I used some of these and have them screwed to a piece of plywood in the enclosure where my charge controller is mounted. It's not code, but if locked up is safe.
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shovelshort
Member
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# Posted: 21 Jan 2012 20:24
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Thank you so much. Some of this is over my head, but you have definitely pointed me in a more comfortable direction. This also gives me some information to look up and better educated myself.
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kenl
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# Posted: 23 Jan 2012 20:51
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IMHO I would get on ebay and buy a 12/24 mppt charge controller @ 20-30 amps output for around $100. For panels the 200w KD solar panels from sunelec @ $176 each. For an inverter maybe a 1000w continous from Harbor Freight or someplace like that (maybe ebay again). A large inverter if you don't need the watts are not very efficient. The SQD breakers are rated for dc use to 48vdc max so you could go with them if you wanted. Code does not require over current protection on a 12 vdc system on the solar side.
If your a member of costco or sams club source your batteries locally, 2- 6v golf cart batteries @225 amp hours.
Put a 125-150 amp car audio fuse between the battery bank and the inverter these can be bought online and the holders also. Buy extra fuses.
I live in a 1800 sq/ft house that is 80% off grid. if you need a basic drawing of what to do email me kenn1962 at hotmail dot com , no spaces in address. Put small cabin in the subject line so I don't trash it. I don't sell solar or any of the other products listed above.
kenny
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shovelshort
Member
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# Posted: 3 May 2012 16:45 - Edited by: shovelshort
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It has been awhile and here is where I am at now. I have purchased the following:
(1) MPPT30 solar charge controller 12V/24V/48V 30A max current
(1) Xantrex XPower 1000W inverter 12V battery system compatible only
(1) Sharp 230W Polycrystalline panel VOC-36.9V Isc-8.45A Vpmax-29.3 Ipmax-7.85A 600volts max
I know I need all the appropriate length/sizes of cable once I figure out where I am placing everything. Right now I am just trying to figure out what to buy battery wise. The inverter literature talked about amp hours and such.
I was going to look at Crown batteries. Their manufacturing center is by my in-laws (2 hours away) and they have a scratch/dent showroom. This will probably still be expensive and I don't know when we will be up there next. Anyhow looked at some golf cart batteries at Sam's club. They have a 12V battery for $184 with a 20amp hour rate of 155. They also have a 6V battery for $88 with a 20amp hour rate of 230.
I would think that I should buy two of the 6V batteries and place them in a series circut to make 12V. So would this give me 460 amp hours?
I sent something way back to you Kenny about some drawings and didn't see anything back. My solar controller directions have a diagram showing the solar panel, the battery, and the loads all being wired to it. It has 3 pairs of +- screw terminals. I assume that I should run some outlets through the cabin wired to a plug plugged into the inverter right?
I also have a harbor freight 800W generator to use as back up. I know to send it's power to the inverter but how is it wired?
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MtnDon
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# Posted: 3 May 2012 17:54 - Edited by: MtnDon
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I'd go with the 6 volt batteries.
Quoting: shovelshort They also have a 6V battery for $88 with a 20amp hour rate of 230........ two of the 6V batteries and place them in a series circuit to make 12V. So would this give me 460 amp hours?
That would be still 230 amp hours.
Batteries in series; add the volts, amp hours stay the same.
Batteries in parallel; add the amp hours, the volts stay the same.
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shovelshort
Member
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# Posted: 3 May 2012 20:44
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So...if I run the two 6v batteries in a series to make my neeeded 12v what do I do if I want to add batteries and increase amp hours? Do I add the third battery in parallel with the second battery and so on?
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CabinBuilder
Admin
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# Posted: 4 May 2012 10:31 - Edited by: CabinBuilder
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Batteries in series: add the volts, amp stay the same, add the amp hours.
Batteries in parallel: the volts stay the same, add the amps, add the amp hours.
In either case, doubling the number of batteries will double energy storage capacity,
i.e. double amp hours.
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MtnDon
Member
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# Posted: 4 May 2012 11:05 - Edited by: MtnDon
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Sorry cabinbuilder.  What I stated was and is exactly correct.
Batteries in series; add the volts, amp hours stay the same.
Batteries in parallel; add the amp hours, the volts stay the same.
However, in both cases the watt-hours increase. There is a difference.
Reference HERE this link is aimed at the power scooter user, but the electrical principles remain the same for any type of battery.
...and HERE
Amp-hours is a poor comparison for total capacity anyhow. Watt-hours means more. Volts x amps = watts and volts x amp-hours = watt-hours. Amp-hours capacity means nothing without knowing the voltage.
You are right of course, that adding batteries adds capacity. That much is obvious. The terminology used, amp-hours and watt-hours has to be watched though as amp-hours is voltage dependent to really mean anything.
All examples assume the batteries all have the same voltage and the same or very close to the same amp-hour ratings. (If inserting batteries of lesser amp hours with others the system will be limited by the batteries with the smaller amp-hour rating. This is part of the reason it is a bad idea to add new batteries to an older battery or set of batteries.
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MtnDon
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# Posted: 4 May 2012 11:16 - Edited by: MtnDon
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Quoting: shovelshort So...if I run the two 6v batteries in a series to make my neeeded 12v what do I do if I want to add batteries and increase amp hours? Do I add the third battery in parallel with the second battery and so on?
If you have one series string of two 6 volt batteries you can double capacity by adding a second series string of two 6 volt batteries and connecting the two strings in parallel.
Example in photos. 12 batteries, three series strings of 4, series strings then connected in parallel using buss bars. 15,120 watt hours; 24 VDC x (210 amp-hours + 210 amp-hours + 210 amp-hours) = 15,120 watt hours capacity.
series/parallel for 24 VDC
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buss bar, negative connections
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buss bar, positive connections
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bugs
Member
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# Posted: 4 May 2012 11:47
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Hi Ahunter
We have a smaller cabin 8x12 and we went with the setup that was put together by a local dealer. They asked us all the questions that people have posted above and came up with these specs: One 130 W Solar Panel Array, three 2.7 kWh Maintenance Free Batteries, 1800 W Inverter / Charger, 30 A Charge controller with meters. Rating: output (kWh/year): 167 or (kWh/day): 0.5. Then they assembled it so it was a "plug and play" that even I was able to install.
We also went with commercially available LED bulbs for lighting rather CF bulbs as they have too many issues (don't like the cold, when they break it is hazardous and disposal is a problem due to the mercury in them) we felt.
The system enables us to run a fist load of LED's, charge up netbooks, phones etc. When fully charged there is enough juice to run a 900 watt microwave to warm up supper or a cup or two of water. The setup can also handle a 1200 watt electric kettle to make a litre carafe of morning coffee.
We have been very happy with the convenience that the system allows us.
But as mentioned above this is what we did, your situation and requirements may be very different.
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Sarge
Member
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# Posted: 5 May 2012 08:26
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For an old mans clarity if you will.
You say a 2.7kWh battery. Is this a 12v 225 amp battery?
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shovelshort
Member
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# Posted: 20 Jul 2012 18:02
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This is off topic, but can I charge a 12V battery with a small panel that is putting out about 8V.
I have a game camera that eats throw away batteries and I want to put together something more economical. I have the panel from one of those security lights from Lowes that broke. The camera has a 12V input.
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MtnDon
Member
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# Posted: 22 Jul 2012 17:07
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Quoting: shovelshort can I charge a 12V battery with a small panel that is putting out about 8V.
No.
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shovelshort
Member
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# Posted: 28 Aug 2012 00:16 - Edited by: shovelshort
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This is the Solar schematics I created for what I want to do. Is this correct? or overkill? suggestions?
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Dillio187
Member
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# Posted: 28 Aug 2012 06:02
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run the inverter directly off the batteries, not the charge controller. Also, you do not need to fuse your single solar panel. Looks like a good starter system for you, it is real similar to what I am installing at my cabin.
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MtnDon
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# Posted: 28 Aug 2012 10:24 - Edited by: MtnDon
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Ditto the thought about the fuse at the PV module; not needed.
Is that disconnect rated for DC use?
Also ditto the inverter connections. The inverter connects directly to the batteries. A type T fuse should be in the inverter + connection, sized for the maximum draw of the inverter. 30 amps for that seems small unless you plan on only having a very small inverter. Note, I also use a HD DC breaker as a disconnect after the fuse. see solarseller.com for a sorce on big DC breakers.
The output of the charge controller should go through a disconnect or DC rated circuit breaker but it should be separated from the other disconnect.
You can use DC rated circuit breakers as disconnects if they are sized correctly to amps and max peak Voc voltage. solarseller.com sells assorted Dc rated breakers.
Everything should be grounded. (NEC does allow 12 volt DC systems to be ungrounded, but grounding increases the system safety.) However, there can be an issue with some cheap inverters. Some have an internal ground and if a system ground in introduced they can loose their magic smoke, they burn out. Use an inverter that has an external ground lug, otherwise you may have problems. Or don't ground the system. (If the inverter has built in receptacles then it is a virtual certainty it has an internal ground.)
If the components are all reasonably close together the best way to ground the system is to install a ground block or a ground buss bar someplace. Then run a ground wire from each component to that block. The batteries negative is connected to the ground at one point. The idea is to connect the grounds in a manner that will leave all the other components grounded if any one component is removed from the system for any reason. Then run a single ground wire to the 8 ft ground rods. Two ground rods are better than one; place 8 feet apart at least.
Lightning arrester: install a DC rated one at the PV modules. It gets connected to the grounding system and across the DC positive and negative PV outputs. Do ground the PV module even if you do not ground the entire system.
Keep the electronics physically separated away from the batteries.
Some charge controllers are set up / programmed more easily if the is a handy simple disconnect on their input and output sides. Using a DC breaker as a disconnect right there at the charge controller location makes that simpler than undoing wires or whatever. On another note: if the charge controller has an external ground lug then it too should be grounded.
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CabinBuilder
Admin
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# Posted: 28 Aug 2012 12:27
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As always, very informative, MtnDon - Thanks.
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Anonymous
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# Posted: 28 Aug 2012 19:08
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Quoting: shovelshort (1) MPPT30 solar charge controller 12V/24V/48V 30A max current(1) Xantrex XPower 1000W inverter 12V battery system compatible only(1) Sharp 230W Polycrystalline panel VOC-36.9V Isc-8.45A Vpmax-29.3 Ipmax-7.85A 600volts max
Above is what I already have purchased and in hand. I drew up the schematics to figure out what wire, fuses, and disconnect to purchase.
So don't use the output on the charge controller marked "loads" huh?
The inverter does have a ground screw on the outside shell/case.
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Anonymous
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# Posted: 28 Aug 2012 19:10
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My brother in law also got me two scissor lift batteries too. I haven't picked them up yet and don't know their specs.
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shovelshort
Member
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# Posted: 28 Aug 2012 19:53
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Better?
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MtnDon
Member
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# Posted: 28 Aug 2012 21:42
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Quoting: Anonymous So don't use the output on the charge controller marked "loads" huh?
What are the sets of terminals all marked? Or better yet what is the make and model of the charge controller?
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MtnDon
Member
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# Posted: 28 Aug 2012 21:43
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"loads" could refer to a "diversion load" which is something that is needed when a charge controller is used on a wind turbine setup. PV systems do not require a diversion load.
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MtnDon
Member
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# Posted: 29 Aug 2012 00:43 - Edited by: MtnDon
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The disconnects in the drawing, should IMO, be separate or individual in case there is a need to pull just the input for example. The only reason I mention that is that some controllers require connection to the batteries first so the controller can be programmed to the voltage etc. Then they are connected to the PV array. Simpler with separate disconnects or breakers.
That 1000 watt inverter will likely draw something like 85 amps at full power, maybe a bit higher due to inefficiencies. That's why that 30 amp class T fuse is too small. You could use a 30 amp there in the line from the charge controller to protect against a dead short in that line. I'd probably use a 35 to 40 amp in case the CC had a peak. A class T is a quick blow and will not tolerate surges. The inverter line could use a 110 to 125 amp size most likely, unless the manufacturer advises something else. EDIT: I see Xantrex recommends 150 amps DC; that will cover surges. It should likely have an AIR value of 20,000 amps DC to be safe.
Then there is the question of wire size, which is dependent on length of run and maximum current load.
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shovelshort
Member
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# Posted: 29 Aug 2012 21:32
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I think I am just going to buy this set up and sell my inverter and charge controller. Any takers?
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MtnDon
Member
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# Posted: 29 Aug 2012 23:40
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I didn't mean to discourage you. Selling is probably not really necessary, but knowing exactly what equip you have makes the task of offering good easy to follow advice a tad easier.
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creeky
Member
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# Posted: 31 Aug 2012 19:42
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Shovelshort: Your schematic looks good.
You only need a 15 amp fuse in the combiner box for your solar panel.
Change 30 to 100 on the inverter fuse.
That and a piece of board to mount it all to and yer good to go.
The Missouri panel doesn't seem to have a mppt controller, which you speced and I assume already have. The inverter is modified sine wave. Nothing special there. Nice combiner box though!
It always looks so good once you get the bits up on the wall.
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