Questions re parallel installation

paul12345
paul12345 Registered Users Posts: 15 ✭✭
edited July 2022 in Solar Beginners Corner #1
I'm not permitted to connect in series 3 x 455W  @ 41.4 V x 10.92A because that is greater than 50VDC which is proscribed work (only certified persons can do). This is a 12v off-grid installation.
So now I have to look at a parallel installation which keeps the volts below 50. I would prefer then to parallel 3 x controllers so the system can still produce if one of the controllers fails.
Q1. When looking for suitable controllers, can I safely assume real world watts of this panel is actually 455 x 0.85 = 387W?
Q2. I would like to install one of the controllers inside a cabin. Would the read-out of the cabin controller be that of the whole system, or just that part to which the actual controller is attached to?
Q3. Any controller that could be recommended or a site you know of which I plug in the numbers? The owner wants MMPT with wifi or bluetooth but I dare say I could persuade otherwise if too expensive.
7 x 150w panels through PWM TriStar TS-45, into 220 AH Crown battery bank.

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    Longer term, could you apply for an "Electrical Installer" (2-year work experience) for your systems (or hire somebody). Guessing you are in New Zealand?

    https://www.ewrb.govt.nz/becoming-an-electrical-worker/registering-with-overseas-qualifications-experience/working-in-new-zealand/
    https://www.ewrb.govt.nz/becoming-an-electrical-worker/training-qualifications-and-requirements/

    The other question I would have--Would you not have the same "limitations" and not be able to install an AC inverter with 240 VAC output?

    If you are installing MPPT (maximum power point) charge controllers, I use around 0.77 (others can use 0.75) derating (roughly 0.81 for panel derating for warm to hot weather * 0.95 for charge controller eff = 0.77):
    • 455 Watt panel * 0.77 derating = 350 Watts typical max peak wattage
    • 350 Watts / 14.5 volts charging = 24 Amp minimum (optimum) charge controller rating..
    For example, 3x 30 Amp MPPT charge controllers would work.

    Or, 1x  (3 * 24 amp = ) 72 Amp+ rated (at 12 volts) MPPT charge controller.

    You would have a bit of an issue with trying for 3x 41.4 Vmp (?) panels in series... Need to know the Voc (voltage open circuit) ratings of the solar panels you want to use, and the minimum temperature where they will be installed...

    The "typical" MPPT charge controllers have a maximum Voc (Vpanel-max input) voltage of 100/140/150 Volts... Voc (and Vmp) rise as temperature falls. Need to insure Voc-cold-array is less than the max Panel Input Voltage of the MPPT charge controller you choose.

    Longer term, figuring out how to install higher voltage solar arrays (max input voltage of 100/150/600 volts) would be good for long term business opportunities (I would thing). Working with high(er) voltage solar arrays allows you to use smaller diameter copper wire, and install the solar array farther away from the Power Shed/Home/etc...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • paul12345
    paul12345 Registered Users Posts: 15 ✭✭
    edited July 2022 #3
    Thanks Bill many years ago I attended a foundation course on 'electrical worker' but it was very limited as to what type of work could be done. It would have been difficult to be self employed and was more biased toward big employer requirements.
    Most I know don't use inverters via cabled 240VAC mains wiring and multiple socket outlets, instead they prefer using them via DC accessory sockets. This may in part be due to, though it is legal to DIY your own home AC, getting it certified by a qualified electrician can be extremely difficult. 
    For some reason many 30A mppt controllers here in NZ are either out of stock or overpriced, which I expect may have something to be about them being, seemingly, a popular choice. 
    Most can be purchased from the USA cheaper than NZ, but then there are warranty issues if the item has to be fixed.
    Well, swings & roundabouts so it is said at least in this part of the world.
    7 x 150w panels through PWM TriStar TS-45, into 220 AH Crown battery bank.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    Victron has been pretty popular with folks--Including Caravan owners. Here are some examples (that I know of) from our host here in Arizona, USA:

    https://www.solar-electric.com/search/?q=victron+mppt
    https://www.solar-electric.com/victron-energy-venus-gx-communication-centre.html

    https://www.solar-electric.com/mnclassic.html (via Ethernet Cable)

    I am not in the solar business--Perhaps some other folks here can give you some other ideas--Especially in the ANZA region.

    Regarding wiring, can you do something like wire up the solar array (they are usually done with plug in wiring), and have the customer make the final connections (strip wire, put under screws in breakers/charge controllers after the sun has set)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • paul12345
    paul12345 Registered Users Posts: 15 ✭✭
    No, legally if more than 50VDC I can do the wiring but would need a certified electrician to liven the system. Hence it is the electrians responsibility to validate the system before livening.
     In this case though the owner has since decided to prefer the parallel option for reasons of built in robustness if any one of the controllers should fail.
    Thanks for the links & excellent information as usual.
    7 x 150w panels through PWM TriStar TS-45, into 220 AH Crown battery bank.