I’m currently working on the schematics of an Off-Grid system i’m going to build next year, i’ve worked before on more simpler systems, so i’m not a beginner but neither an expert on this field.
I’m leaving here the general specs of the system and the current scheme of the idea, if anyone have any suggestions, spot some mistakes or just want to comment anything, please, you’re all very welcome to do so and i thank you in advance for your help!
Ok, but if the peak needs of the entire system is calculated around 35 kW ( this is why the 3 quattros in parallel ) , would 15kW from 3 phase be not enough?
I know that 3 phase it’s more reliable, but in quattro manual they say it can be parallel connected up to 4 units, so it shouldn’t be a problem, no?
Because not everything that is possible also makes sense.
In a 3 phase system your current levels are much lower, so your wiring and fusing is easier to configure.
And i don’t believe you’ll get a fitting 1 phase generator in this size, the minimum current of a 15kw mp is very high, the generator has to supply this x3.
But, first of all the 15kVA are actually 12kW at normal temperature in optimal contition ( per Quattro datasheet ) so the estimated kW are 36 in total when/if conditions are optimal, then there is the already commented need for this system of around 30-35 kW at peak conditions, so i can’t have a system capped at 15kVA ( it will be 12 kW ) with a three phase configuration, i need more kW. The only solution with a three phase would be to have 9 Quattros, 3 sets of three units in 3 phase, outputting 12*3=36kW in 3 phase, solving the issue, but making it inaccessible triplicating the cost of the inverters only.
Now, i agree about the wiring and fusing, but if you take a look at the schematics i’ve uploaded, you’ll see that everything is adjusted to specs, and currents levels ( if i didn’t make any mistakes ).
Please, if you thinks something is technically wrong with the configuration, explain it a little, because even if your opinion can be usefull to look from a different angle, is still just an opinion.
Why should i consider wrong the product manual from VIctron?
6 sets of three units parallel connected provide 75 kW / 90 kVA
that means 1 set of three units, as you suggest, provide 12.5 kW / 15 kVA, the 3x12kW is not correct.
I don’t know if there is some misunderstanding here, but three phase configurations don’t sum up the device output capabilities, that happens only with the parallel connection.
The 35 kW demand is because the residence it’s calculated for a max. of 16 person, so it’s like a big home, with standard appliances, there is no need of special high demands appliances, anyway.
It is right what you where saying, i had the wrong manual. So thank you for the correction/suggestion, and considering that, obviously three phase configuration will be a lot better!
About your solar panels: 48.3V Voc x 9 is near the maximum of 450V and will kill your RS450 when the temperature ever drops below 10°C (assuming a temperature coefficient of -0.25%/°C).
What happens in a 3 phase system where 1 Multi or Quattro fails? Do the remaining phases keep working? And in a single phase system with parallel units? Perhaps a consideration in such an event.
Yes, you’re absolutely right, i didn’t considered the temperature drop in winter, charts shows a minimum temperature around 10 degree celsius in winter during the day in the area i will install this system, but it could be lower sometimes.
The temperature coefficient of this panel i choose is -0.25%/°C, so at 10 degree with 9 panel in series the Voc voltage should be 451V, thus killing the MPPT
Thanks for the suggestion, i have two choices, scale the arrays to 8 panels, or add 4 more panels and make 5 arrays of 8 panels, switching one MPPT 450 | 100 to the big brother 450 | 200 with 4 input lines.
I don’t know the answer to those questions, it will need some research, but anyway i suppose that in case of a component failure, the system should shutdown and the generator should kick in as backup. Anyway, it’s worth to find some more info about the subject, thanks!
There may be an alternative, look thru the panel choices, they come in different cell counts (72 vs 60), so there might be models that have a Voc of about 40V – I recently designed an array with 9 panels in series for this cold climate here where we’ve seen -20°C occasionally and found that those lower-voltage (and higher-current, obviously) panels gave me the margin I needed. But those were 1100x1700mm² panels in the 450W range, no idea what’s available in your chosen size.
