Input on Proposed Wiring

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mjp24coho
mjp24coho Solar Expert Posts: 104 ✭✭✭
in Solar Beginners Corner #1
I’m seeking any input any of you may have on my proposed wiring below. I’m installing three new panels to power a Grundfos solar pump I’m having placed in my well. My pump is currently run off a generator and a 11OV ½ HP pump that I would like to replace with a Grundfos. I have (3) 175W suntech panels that I will use to power it, and a generator as a backup. The panels are rated at 35V Vmp, and my plan is to wire 3 together for 105 Vmp. The panels are located 15’ from the combiner box (wired with 10 AWG from the panels to the combiner box), and the combiner box is 110' from where the pump controller will be - I will run it in 6 AWG THHN wire from the panels to the controller. From the controller to the pump (50' to well head plus 120' down the well), it will be wired with existing 12 AWG wire. I'd prefer to not have to dig that wire up and replace it with new wire. I calculated the voltage loss at just over 3%, which isn't ideal, but I can live with that.

My questions are twofold:
(1) Anyone see any issues with the above?
(2) My plan is to run the 6 AWG THHN wire (stranded, with two separate wires – positive and negative) in 1 ½” PVC conduit, which will be buried 12” underground. The 10 AWG MC4 wiring form the panels to the combine box will not be in conduit (exposed on the roof). The conduit from the combine box will run 15’ down the side of the house, before going underground all the way to the controller. Any issues with heating with the 2 wires (6 AWG) running together in the same conduit, at over 100 Vmp?

Any thoughts of feedback would be appreciated. Thanks.

Mike
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
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    Re: Input on Proposed Wiring

    Be sure you are getting all the parts, I think there is a several hundred $ Grundfos pump controller that is required, that has the "brains" in it.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #3
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    Re: Input on Proposed Wiring

    It sounds OK for wire size (what current are you designing for? ~6 amps maximum?).

    Regarding the buried power line--I believe US code requires 18" deep minimum.

    And I would suggest a larger pipe (with long bends) to bury the wiring (4" or larger?)... Would allow you to pull new cable later (larger pump) or to add some other control/monitoring lines too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
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    Re: Input on Proposed Wiring
    BB. wrote: »
    And I would suggest a larger pipe (with long bends) to bury the wiring (4" or larger?)... Would allow you to pull new cable later (larger pump) or to add some other control/monitoring lines too.

    -Bill

    4" is huge. I pulled 3, #6 wires in 1.5". it was tough, 2" would have been better. 2.5" would be enormous, and should hold 4, #4 cables easily.

    digging the trench is the hard part.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #5
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    Re: Input on Proposed Wiring

    I was "cheap" -- I just buried black ABS pipe for some wiring... And no matter what size I put in, I always wished I put in the next size up (easier pull, easier to add wires later). :roll:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #6
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    Re: Input on Proposed Wiring

    Just help pull 4 conductor #1 in a 2 inch, not recommended through the back to back LBs required. (in retrospect one could have been a 90 sweep)
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  • mjp24coho
    mjp24coho Solar Expert Posts: 104 ✭✭✭
    #7
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    Re: Input on Proposed Wiring

    Great input - thanks all. Regarding the pump, I'm also getting the IO-101 inerface and the CU-200 controller. Based on everyone's input, I think I'll run two separate lines of 2" conduit - two wires in each. I'll bury it 18" deep - won't be hard since I'll be renting a trencher.
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