Where I want to install panels

I have a 600 square foot out building with south facing roof, with 3/4 of the roof made up by the south slope with no trees around. 
This is where I want to put the solar panels.
It has a 100 amp QO sub panel. I already have to dig up the wire going out there, since it's on a 60 amp tand breaker running 6/2 with ground, with the neutral and ground both running on what appears to be a 10ga solid bare ground. I didn't do this the last guy did.
The 100 amp panel should be able to accept 20 amps of solar, or nearly 5kw. There is no where near enough room for 5kw of panels on the roof, no problem there.
Would it be objectionable to run 6/3 with ground on a 50 amp breaker out there from the main?
Only loads on the sub panel will be a 3/4hp well pump and some lights, plus maybe 2 or 3kw of panels.

Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

Comments

  • ILFEILFE Solar Expert Posts: 364 ✭✭
    oil pan 4 said:
    I have a 600 square foot out building with south facing roof, with 3/4 of the roof made up by the south slope with no trees around. 
    This is where I want to put the solar panels.

    ------------------------------- truncated ----------------------------------

    There is no where near enough room for 5kw of panels on the roof, no problem there.
    If you have about 450 square feet of available roof, you should be able to mount up to about 4.5 kW of panels there.

    Just thought I would mention that, before you determine wire size / run.
    Paul
  • EstragonEstragon Registered Users Posts: 1,810 ✭✭✭✭
    Just to clarify, the plan is to invert the DC from the panels to 240v split phase AC into the shed sub-panel, and backhaul that on the 6/3 to a main panel?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • mike95490mike95490 Solar Expert Posts: 7,407 ✭✭✭✭
    Be aware many jurisdictions require firefighter walkway routes on the roof, you may not be able to fit as many as you hope to.
    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 ,

  • ILFEILFE Solar Expert Posts: 364 ✭✭
    mike95490 said:
    Be aware many jurisdictions require firefighter walkway routes on the roof, you may not be able to fit as many as you hope to.
    I keep forgetting about living in a jurisdiction with strict laws. 
    Paul
  • oil pan 4oil pan 4 Solar Expert Posts: 661 ✭✭✭✭
    Yes power inverters would be located at the 600 square foot building. I don't want to try and send DC any distance.
    I wasnt planning on covering every square inch with panels, was going to leave room to get around and under the panels some what.
    I have no shortage of room for panels other places.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • Wheelman55Wheelman55 Registered Users Posts: 41 ✭✭
    Oil Pan. I'll let the experts give you the details. Two things: #1. it's relatively inexpensive to move dc if you string your panels up in series for high voltage and low amperage. DC can be moved long distances with smaller wire.  Meaning that your panels can be installed on the ground away from your buildings.  #2. Running the 240 AC will take larger wire. In both cases use a voltage drop calculator to tell you what gauge wire to use for the runs. Southwire has good apps for voltage drop, conduit fill and box fill. 

    Best of luck with the project. 
    Building Off-Grid in Terlingua, TX
  • oil pan 4oil pan 4 Solar Expert Posts: 661 ✭✭✭✭
    I'm most likely going to avoid higher voltage DC if possible, try to limit it to 48v.
    The AC power wires joining the out building to the house are most likely going to be to be 6/3 with ground.
    Plus why would I want to wire all my panels together? So that a shadow or single leaf landing on the panels can cut my entire string power production way down.
    I already need power out in that building, for well pumps, yes I may run more than 1 since I have a 16 inch bore well that was tested to do 100gpm, I may run a welder out there some and for future expansion.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • Wheelman55Wheelman55 Registered Users Posts: 41 ✭✭
    oil pan 4 said:
    I'm most likely going to avoid higher voltage DC if possible, try to limit it to 48v.
    The AC power wires joining the out building to the house are most likely going to be to be 6/3 with ground.
    Plus why would I want to wire all my panels together? So that a shadow or single leaf landing on the panels can cut my entire string power production way down.

    Have you considered series/parallel?

    Building Off-Grid in Terlingua, TX
  • oil pan 4oil pan 4 Solar Expert Posts: 661 ✭✭✭✭
    The panels would be parallel.
    Panels in the 250 to 350 watt range, which I was planning on using should already be 48v.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • EstragonEstragon Registered Users Posts: 1,810 ✭✭✭✭
    Most panels I've seen in that size range are ~30-40v - not enough for 48v in parallel.

    My 250w run low 30s unless really cold, which can get them to mid 30s. Even when it's really cold, once the sun warms up the panels, the voltage goes back down.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • oil pan 4oil pan 4 Solar Expert Posts: 661 ✭✭✭✭
    Sound like "24v" panels.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • Raj174Raj174 Solar Expert Posts: 519 ✭✭✭✭
    Probably not, 24 volt panels have 72 cells at 36 to 38 volts VMP and are usually 290 watts or higher, although there are some around 200 watts. 
    12 x 300W Renogy PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 195AH HI Power LiFePO4 no BMS, 4000W gen.
  • littleharbor2littleharbor2 Solar Expert Posts: 745 ✭✭✭✭
     The older 24 volt, 72 cell panels are comprised of 5" cells and ran upwards of 200 watts. The Sunpower 72 cell panels did go up to about 230 watts. These were all approx. 32" x 65"

     Todays 290 watt plus 24 volt panels are composed of 6" cells.  They have a typical size of approx. 39" x 78"

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • oil pan 4oil pan 4 Solar Expert Posts: 661 ✭✭✭✭
    That's what I will be looking for then.
    I would like to have the ability to go off grid some day and 48v panels or panels that can be series paralleled for 48v would be ideal.
    If not then series parallel 30ish volt grid tie panels for close to 48v panel voltage then use a MPPT charge controller that can handle off voltage panels.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • Raj174Raj174 Solar Expert Posts: 519 ✭✭✭✭
    @oil pan 4
    If considering charging a 48 volt battery with an MPPT controller, you can't do much better than three 60 cell panels in series. VMP will be about 93 volts. Two 24 volt (72 cell) panels in series really does not produce high enough VMP, only about 73 volts, for the MPPT controller to work properly with a 48 volt battery, especially with FLA batteries. Some people have this design without problem. I even use this design in my system, but I have LFP batteries and do not require EQ level voltage,  and even then I had to use Legacy MPPT tracking. Best not to design a system with the PV on the low end of acceptable voltage. IMHO

    Rick
    12 x 300W Renogy PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 195AH HI Power LiFePO4 no BMS, 4000W gen.
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