Good morning. I am trying to understand parallel multiplus-II 48/1000, or 48/15000 for off-grid only, and no generator.
Is this a supported setup?
I read in the manuals about the transfer switch for these unit, for a generator. I wont have a generator. Do i still require a transfer switch?
Is there any other things i need to understand for an off-grid install.
as example
total load = 18kW max, normally max out at 12kW but the install could theoretically hit 18kW if everything turned on.
Install is 3X multiplus-II 48/10000 ac coupled to 3X fronius primo 8.2kW solar inverters. (assume all the other good stuff is design correctly , eg batteries, Gx, etc). There is no grid connection and no generator.
@chad
Yes, you can combine 3x MP2 10k or 15k with 3x Fronius 8.2k. Fronius need to be connected an AC_out with the loads.
Without a grid and no generator there is no transfer switch needed. The transfer switch is needed to switch the loads between MP2 AC_out and generator/grid in case of maintenance of MP2.
Generator/grid would be connected to AC_in.
Please mind Victron is 10kVA not 10kW. With cos phi 0,8 a 10kVA delivers 8kW.
For 18kW peak, I would go with 2x MP2 15kVA.
If you refer to 18kW AC-PV charging to battery, mind the chargers Amp, which is 140A (7kW) for the 10k and 200A (10kW) for the 15k.
From a statement design perspective I recommend substituting two Fronius by 2x RS 450/200 to efficiently charge the battery unless the waste majority of you loads can be managed according to current PV, direct usage of AC-PV.
Ac coupling: The Fronius and Victrons as coupled on the AC side of the system. (eg Fronius produces AC from the solar panels, then the Victron uses AC –> DC to charge batteries. When no solar Victron provides Ac from the batteries. This cycles the batteries less as the AC is used direct from the Fronius during the day.
Why: Multiplus-II is cheaper than Quattro (AUD$35000 versus AUD$2500). I dont have any use for the extra features as I am off-grid.
Thank you for info. Please review and if you see any mistakes let me know
The majority of loads are~1pf (cos phi), as heaters, inverter reverse cycle aircon/water heater, lights. small number of DOL motors like fans. 2 large motors (3kW are inverter). The Battery is a custom LFP for 5 days not sun (I live in subtropical area) incase of low sunshine or lots of cloud or cyclone/hurricane/typhoon
OK it sounds like it is as I thought. The Victron cannot switch the load to generator/grid if greater than the capacity of the individual unit (makes perfect sense as big contacts cost lots).
I was originally thinking about 2X MP2 15k. I read Victron inverter/charger kVA ≥ Total AC‑coupled Fronius kW (AC-coupled PV with Fronius PV Inverters [Victron Energy]). The 1:1 rule. Therefore if I have a MP2 15k fail I would have to turn off 2 Fronius until MP2 15k repaired. I changed to 3X MP2 10K so if 1 failed then I switch off 1 Fronius and still met the 1:1 rule. Bonus benefit is with 3X MP2 10k it is N+1 so full load can be covered by the 2 remaining MP2 10k.
Charge current: From my understanding when parallel you set the charge current. With 3 the same combo Fronius–MP2 10k then set charge current (limit to mas out of Fronius) then all good. if one unit breaks (fronious or MP2 10k) I turn off one unit on the other side and all setting still work for the charge current.
The solar is 10% oversized for the Fronius (28kW panels for 24kW solar inverters). The load actually includes an EVSE for an electric car, with intent to setup EVSE so uses AC only (there is override button to allow EVSE charging from battery if essential to charge car). Most big loads (motors, cooking, EVSE, big aircons) are during the day (Fronius) and much light loading during night (Victron).
You can couple on the AC input or Output (preferred). Hence the question.
Re N+1, remember if a unit fails the entire system is offline. You have to manually isolate and reconfigure the system to continue supplying power. There is no automatic recovery.
@chad
The MP3 can do load shifting with grid or generator, but you stated no, grid no generator.
For offgrid systems you need for every kWp PV three kWh battery. In your case 24kWp give 72kWh battery.
If grid tied, we talking about ESS energy storage system. There are different options to either run on PV/batterie before using grid or do load sharing.
With a generator there also different options like automatic recharging batteries.
If you want connect grid and generator you need to use Quattro having ACin1 und ACin2 with different settings (grid code) instead of MP2.
NICK: I understand your question now. I thinking AC coupling on the output.
Yes not a true N+1 setup. It’s more that no part required, turn off some isolators/switches, software reconfig (probably a saved file upload or pre-written sheet) and I back online.
The solar arrays are 6 strings total across 3 fronius. There plenty of redundancy in that side.
BJORN: Ok I think I have some learning here. I not sure what you mean about 3:1. Are you talking about storage capacity to cover nighttime/cloudy days. For that I have a 124kWhr custom built battery (30kWhr per day * 4 days no solar production = 120kWhr). I live in sub-tropics and get affected my rain depressions and cyclone/typhon/hurricane.
No grid. The nearest grid connection is over 100km away (install for remote/rural area).
Generator: I was going to ask later if it possible to setup a small generator as a battery charger type generator (eg 2KVA) via AC in and set the charge current on each MP2 to 0.5KVA (3*0.5=1.5kVA). Its not to takeover and supplied load it is just an emergency battery charger option.
My planning is to start simplest and work toward complex. eg build a single setup first (1 MP2 and 1 Fronius) to get that working first. Then get MP2 paralell working (1 fronius and 2 MP2). Then add 2nd fronius. Then move to 3 MP2 and 3 fronius. (I will buy 3 MP2 at same time to ensure all same build out of factory).
Any other items I should be researching deeply to best understand if i am on the right track or not.
For your 30kVA MP2s (3x10k or 2x15k) you need 90kWh of battery. With your 128kWh battery you are well above.
Yes, you can add a small generator and let Venus OS automatically start and stop the generator to charge battery automatically.
Some AC generators cause issue. A save way is a DC generator with AVR. Premium are HATZ fiPGM.