Combiner box - Amps?

Hi,
I have a basic question:
If I combine two strings into a combiner box and each string is producing 18 amps each with each string producing 150 volts. When I combine the two strings into a combiner box and then take the single output and connect it to the inverter, does the amps add up going to the converter and/or does the voltage add up?
Comments
Adding power sources in series--The voltage adds.
https://www.allaboutcircuits.com/textbook/direct-current/chpt-5/what-are-series-and-parallel-circuits/
Make sense? If not, please ask more questions. Getting the connections wrong can really ruin your day.
-Bill
But the "real question" is what is the voltage/current required by your inverter solar panel input (is this grid tied, or a hybrid system with a battery bank). You need to make sure that the solar array meets the inverter's input requirements.
-Bill
From what you describe, two strings of 18A paralleled would produce 36A and you would need cable to handle that, likely 6ga.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
I am making some guesses here--But I think this is what you can do with what you have...
First, the Combi switch appears to be a combiner with a disconnect. 4x 10 amp circuits each capable of turning off 600 VDC @ 10 amp circuits and a single 40 amp output.
https://www.ecodirect.com/SMA-CS-p/sma-cs.htm
Looking at your solar panels:
Vmp-array = 7 * 30.6 volts = 214.2 volts
Vmp-array = 4 * 38.2 volts = 152.8 volts
First string would run one of the MPPT inputs on your inverter of 175 to 480 VDC
Second string is too low of Vmp-array voltage to reliably start the GT inverter.
Another option would be to connect 1st and 2nd strings in series for ~367 VDC @ ~8.43 amps
You can connect panels that have their Imp in parallel within 10%--And yours are.
That would allow you to use 1 input on the Combi switch (10 amps is "close"--Normally, I would like fuse+wiring to be at least 1.25x Imp of array--If you look at the data sheets, you should find a series fuse/breaker specification (probably around 15 amps for those panels).
You would not need the combi switch for this configuration as the array current is right at its maximum specifications (you may blow fuses over time--weeks/months/years by operating so close to their 10 amp rating). And you cannot put larger fuses in this unit (it seems). And just as an FYI--You cannot (should not) parallel two differently rated Vmp-strings in parallel... Their Vmp-strings, if paralleled, need to match within 10% or better. Like putting a 12 volt battery in parallel with a 6 volt battery (and blocking diodes). The 6 volt battery will do nothing useful.
You can replace the Combi box with a simple properly rated knife/disconnect switch (one circuit) if you need one (your code requirements).
The single array is OK for a 3,000 Watt GT inverter... Roughly, this array would output:
- 367 Volts Vmp * 8.43 Amps Imp = 3,094 Watt estimated array output
- 3,094 Watt array * 0.77 panel+controller deratings = 2,382 Watt derated output (typical maximum, seen on a few days for a short period of time on cool/clear days around solar noon).
So, based on what you have (and the very quick look at the various specifications), that is what I would probably do (all panels in series, a solar array disconnect if needed by your code).-Bill
You can only use two of the MPPT inputs if you add, at least one more, series panels to String 2... And bring its Vmp-array voltage up to, at least, 175 volts (according your your spec screen shot) for reliable operation.
That would be an ideal solution (another panel on your 3 kW GT inverter is fine, not placing "mixed" Imp panels in series--A bit more output from the higher Imp string, and you do not need any combiner boxes--Just simple disconnects per string).
-Bill
-Bill
http://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=16&productCatName=Breakers
This is (similar) to what was used on my home for the 240 VAC GT Solar disconnect (mine is unfused and just a huge pair of knife switches--Circuit breakers are in main panel):
https://www.homedepot.com/p/GE-30-Amp-240-Volt-Fusible-Outdoor-General-Duty-Safety-Switch-TG4321R/202978635
You probably have to call SMA or a company such as our host (NAWS) about the proper disconnect for your installation. High voltage DC switches are just not very common. NEC (National Electric Code) has been changing quite a bit over the last couple of decades--Makes keeping up with the requirements a bit of work--Plus different cities/counties may use different NEC versions or other codes).
From my understanding, no circuit breaker/fuse is going to be fast enough (or have enough of a "gap") to actually do any real protection against lightning.
The typical suggestion is to put good quality surge suppressors just before the equipment (or where the array wiring enters the home), and use those to shunt high voltage surge to earth ground.
https://www.solar-electric.com/search/?q=surge+suppressors
Midnite uses MOV (Metal Oxide Varistors) to short out the high voltage surges (line to line or line to earth ground--typically).
Many other surge suppressors just use a simple spark gap and sand/ceramic powder to quench the arc.
-Bill