Wire strings that face south and west in parallel?

Kgelles
Kgelles Solar Expert Posts: 25 ✭
in PV Installers Forum - NEC, Wiring, Installation #1
Can I combine these two strings facing west with one additional string facing south? All of the panels are identical. Each string would be fused. Combined power would be sent to a Tristar MPPT charge controller. (I have two extra panels lying around. I'm trying to get my batteries float charged earlier in the day, if possible) Thanks for everyone's help so far...Attachment not found.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #2
    Re: Wire strings that face south and west in parallel?

    Solar Guppy, who designed and tested MPPT solar charge controllers... He always said that different array orientations should have different MPPT tracking units per array orientation.

    Personally, if you have the hardware--Why not try it and see how it works. You can plot the data over a day and see if you see oddball behavior (if you see large variations in output power in stable solar conditions), or if the theoretical about is much higher than actual (you could, for example, use PV Watts hourly output reports for both array orientations, then add them together to see what the "optimum" output wattage would be versus actual output).

    You won't hurt anything by trying one controller on both arrays.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Kgelles
    Kgelles Solar Expert Posts: 25 ✭
    #3
    Re: Wire strings that face south and west in parallel?

    Thanks! (I just realized that I had asked a similar question on the forum a little over a year ago...my memory's not the greatest)
    I've moved to a new house and I brought my panels with me and I'm rearranging them. I have more shading issues to deal with now but so far I think I can make it work.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #4
    Re: Wire strings that face south and west in parallel?

    I thought so too--;).

    Anyway, work on the shading issues if you can--those can really help increase production too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #5
    Re: Wire strings that face south and west in parallel?
    Kgelles wrote: »
    Can I combine these two strings facing west with one additional string facing south? All of the panels are identical. Each string would be fused. Combined power would be sent to a Tristar MPPT charge controller. (I have two extra panels lying around. I'm trying to get my batteries float charged earlier in the day, if possible) Thanks for everyone's help so far...Attachment not found.
    I have read a couple of white papers that said that the difference in MPPT for 90 degree different azimuth orientations is so small that the benefits from using dual MPPTs for them is nearly negligible as long as strings do not contain modules with different orientations and shading is not an issue.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #6
    Re: Wire strings that face south and west in parallel?

    Sort of related - - in a way - -
    My mini-micro hydro turbine outputs max power at roughly 32 volts. I have panels yet to be installed, with MPP voltage of 29. As a trial I combined the turbine with 450 watts PV, all fed to the TS-MPPT-60, and the TS had no problems at all handling the situation, no matter the light falling or not on the PVs. In fact, in my case the TS worked better. With the hydro only, like it's had for the last 4 years, it sometimes does double, triple, or sometimes quad sweeps in very rapid succession, trying to nail down the turbine MMP as it's speed changes under different loading, but with the PV wired in, even at night, that wasn't happening. It did however lock onto the PV MPP, which meant the turbine voltage was a bit lower than MPP, but it wasn't enough to worry about, not at all. The voltages were close enough. Once the PVs get permanently installed, I'll probably wire the PVs through a relay that will disconnect them when dark to remove them from the turbine when they're not producing, and when there's no current flow to cause relay contact arcing.
    Tried the same thing years ago with the MX-60, but it had great difficulty finding a common MPP and would often lock on way out of range till the next sweep. The TS by the way, completes it's sweep in the blink of an eye, while the MX, even at the best of times, often labors for sometimes 30 seconds or more trying to find a place to settle down. A huge, huge difference between the two that way. On the other hand, the MX has features the TS does not.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #7
    Re: Wire strings that face south and west in parallel?

    Just to be clear--I believe Wayne and Wayne and KG are typing about the Morningstar TS-60-MPPT solar charge controller.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    #8
    Re: Wire strings that face south and west in parallel?

    I have 500W pointed south, 1500W west, in four sets of 500W. All attached to a single Outback FM-80, has no trouble at all with it. Never had a second CC to split the south panels off to test, but at high noon I see the wattage I expected to see. I don't have an obvious point toward sunset where the south panels quit producing early, just a gradual drop through the day. Can't say about morning, as I have trees and other obstacles to the east.
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