Question About Strings Using Different Panels

AlanRTAlanRT Solar Expert Posts: 57 ✭✭✭✭
We're looking to augment an existing system of 20 Kyocera KC130 panels. We have an Outback MX60 already in the system. Is there any reason why we can't add an Evergreen A 195-fa2 195 to the ends of four strings consisting of five each of the Kyoceras, or does the difference in amperage between these panels preclude this?

Kyocera KC130 - 21.9 Voc, 17.6 Vmp, 7.39 Amps

Evergreen A 195-fa2 - 22.0 Voc, 17.8 Vmp, 10.96 Amps

Strings:

Configuration A - 3,380 Watts

-[130]-[130]-[130]-[130]-[130]-[195]- 131.5 Voc,, 105.8 Vmp
-[130]-[130]-[130]-[130]-[130]-[195]-
-[130]-[130]-[130]-[130]-[130]-[195]-
-[130]-[130]-[130]-[130]-[130]-[195]-

Or should we go this route with five strings, reducing the system voltage and taking a little more wire loss (80' of #4 copper):

Configuration B - 3,575 Watts

-[130]-[130]-[130]-[130]-[130]- 109.5 Voc,, 88 Vmp
-[130]-[130]-[130]-[130]-[130]-
-[130]-[130]-[130]-[130]-[130]-
-[130]-[130]-[130]-[130]-[130]-
-[195]-[195]-[195]-[195]-[195]- 111.5 Voc, 89 Vmp

I know configuration B pushes up closer to the Outback's 60 Amp power limit but we are in a tropical climate and never experience snow or temperatures below freezing. We never see more than 75% to 80% of total panel ratings here.

Comments

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Question About Strings Using Different Panels

    i'd opt for the system in b as the imp of the evergreen is quite a ways from matching the imp of the kyoceras. i don't know what you've got for wire to the controller, but that can be upped even later if you wish and live with a bit more losses in the meantime. maybe just change 1 leg of the run such as the negative lead.
    being close to the limit i can't say how bad it might get at times, but i suspect you'll be alright. there is a modification for the mx60 to go 70a also so if it does hit it do the mod.
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Question About Strings Using Different Panels

    Alan,

    I'd try "B". As you suggest, you'll see a bit more loss in the cabling, but the MX60 will operate a bit more efficiently at the lower input voltage. Also, the 195's will be able to deliver their full Imp instead of being limited by the 130's Imp.

    As niel indicated, the current output limit of the MX60 can be increased up to ~70 A. If you do this, you'll want to make sure your output breaker and wiring is appropriately sized.

    HTH,
    Jim / crewzer
  • AlanRTAlanRT Solar Expert Posts: 57 ✭✭✭✭
    Re: Question About Strings Using Different Panels

    As always, thanks much, gentlemen.

    Alan
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Question About Strings Using Different Panels

    I can't let this pass without mentioning what the manual actually says:

    "The default charger current limit is 60 Amps and can be changed for circuit breaker or wire size limitations and is adjustable up to 70 Amps for those of you that actually read this manual." (pg 15)

    Almost as good as "Setting system Voltage with the 'Mind Meld'." (pg 13)

    Gotta love a company with a sense of humour. :p
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