Energy System Review

Discussion in 'Off Grid Living' started by DAM29393, Apr 19, 2017.

  1. DAM29393

    DAM29393 Neophyte Monkey

    I am planning on building a shop/office on the back part of my property about 75 feet from my house which is grid connected. I have had Electricians out to bid running a line out to the location and the numbers got me thinking that i could dip my toe into the world of solar for less than the cost of the line and I wouldn't have to dig a trench.

    I recently became over familar with my AC panel thanks to a generator line i recently installed but i'm less familar with the DC side of things so if i'm missing something, let me know.

    The shop is going to be 24x36 with three bays down stairs and an open living space above. I plan to wire it with standard romex, with outlets, switches and fixtures just like an AC setup. Except instead of connecting to grid, i'm going to connect it to my solar/battery setup. Most likely 1 30 Amp breaker and 3 15 Amp breakers.

    My initial design for the setup is:
    4 100W panels (Link)
    Wired to my charge controller 40AMP 24V (Link)
    Charging 4 12v 100Ah AGM SLA Batteries (Link)

    This inverter has outputs that I will wire as the main in a simple breaker panel. Bonus, no need for an interlock, as we won't be attached to the grid!

    So any glaring issues I should know about?
  2. Brokor

    Brokor Live Free or Cry Moderator Site Supporter+++ Founding Member

    What's the climate zone you live in?
    I will let more experienced members post their recommendations, as I am not supremely qualified in this area.
    sec_monkey likes this.
  3. Cruisin Sloth

    Cruisin Sloth Special & Slow

    Bury the cable to power on grid .
    400w is an out house light & a fan with timer .
  4. ghrit

    ghrit Bad company Administrator Founding Member

    Gotta agree with CS. Shop and office loads most likely will WAY exceed 400 watts. Maybe, just maybe, 400 might be the average, but you need to design for peak. What loads do you anticipate, for real?

    Also, standard romex will not do well at 12 volts, and hardly better at 24. There are a few more things to consider ---
    sourdough145 and sec_monkey like this.
  5. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    Your Battery Bank is WAY Undersized... Best you put a 15Amp 240 Vac circuit back there from the Main Breaker Panel... You can do that with some Direct Burial 4 Wire Cable... That is enough for Good LED Lighting, and some computer stuff.. Then use your Starter Solar, as a Beginning, and slowly, as funds permit, build it out... for Grid-Down Backup, that then can be sent back to the House, should that be needed, for Emergency Backup Power, over the same cable... Multiple Sources, to multiple locations, as needed...
    sec_monkey likes this.
  6. Mindgrinder

    Mindgrinder Karma Pirate Ninja|RIP 12-25-2017

    Can't you just get a diesel genny and plug it in straight?
    (total non-expert here)
    sec_monkey likes this.
  7. azrancher

    azrancher Monkey +++

    75'... run a PVC conduit with an 8 AWG cable, my well is 200' run off of a 50 Amp breaker, you could then power a sub panel in the "shop", because solar will never power your "shop".

    Oh and do it yourself.

    sec_monkey likes this.
  8. Cruisin Sloth

    Cruisin Sloth Special & Slow

    Dang , EZ , AZRancher nailed it < BUT 8G AWG is large if the "Kid" is wanting lights & a HFL compressor .
    My shop needs 50 X 60 X 15 high . needs POWER.
    Whats the dream KID ?

    sec_monkey likes this.
  9. oil pan 4

    oil pan 4 Monkey+++

    If you are not running big power tools then 10 gauge should work.
    If you want air compressor and stuff then you want at least 8 gauge.

    With solar, about $1,000 worth of solar equipment is enough to power a refrigerator, while the sun is up. Doubling that budget can buy enough battery to run 24hr.
    sourdough145 likes this.
  10. ghrit

    ghrit Bad company Administrator Founding Member

    Yup, just bear in mind that some day, you might want to do something else in the shop ---. This Olde Pharte has learned to look to the future possibilities, not to just today's wishes and thinking. ALWAYS plan for expansion, like maybe a leanto on the side of the shop for a sandblast booth?
  11. DAM29393

    DAM29393 Neophyte Monkey

    Thanks for the feedback. I was sure I was missing something when i did the math and saw affordability.
    To Answer questions posed, climate zone is NW US (Willamette Valley).

    I don't plan to heat the shop beyond an occasional space heater.

    Had planned to wire the batteries in sequence for 24v, not 12.

    Yes, 400w would not be enough for much...hence the batteries/inverter. This building will not be in use more than 1-2 hours a day, 2-3 days a week. Light power tools (mostly cordless actually), occasional small compressor, a few shop lights. Even the "office" space is just occasional use. Lights, reasonable tv, wireless router. Yes, I will drain the batteries faster than the panels can refill them, but thats the point of batteries right?

    I do have a generator that could supplement if needed.

    I felt that with the charge controller and inverter I chose I was leaving room for future expansion of the battery bank and panels.
  12. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    Just remember that Batteries, Solar, and Charge Controllers, can be rewired, or reprogrammed, for higher Bank Voltages, but the Inverters are FIXED Input Voltage.... Plan your system with that in mind.... when figuring in, for expansion... Also a 15Amp 240Vac feed from the Grid, can be used to slowly keep the Battery Bank charged, and then use the Power from the Battery Bank to supplement the High Power Bursts, used in the shop, when it exceeds the Grid Capability of that Circuit....
  13. DAM29393

    DAM29393 Neophyte Monkey

  14. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    A "Rule of Thumb" for inverters is:

    Less than 1200 Watts 12Volt Battery Bank
    1200 to 3000 Watts. 24Volt Battery Bank
    3000 and Up Watts 48 Volt Battery Bank

    This means you are trying to keep the Amperage Draw under 100 Amps, under Load...
    Also consider just How BIG of Wire you will need to use between the Battery Bank
    and the Inverter, and between each of the Batteries that make up the Battery Bank.
    This is important, to understand.... For ever Volt dropped, in Wiring losses at 12Vdc,
    you will incur a GIANT Power Loss, and Loss in efficiency.
    Tempstar likes this.
  15. Cruisin Sloth

    Cruisin Sloth Special & Slow

  16. oil pan 4

    oil pan 4 Monkey+++

    Sloth is right. Have to get a good power inverter. Preferably pure sine wave if it's going to power anything with an induction motor or power triac.
  17. sourdough145

    sourdough145 Holder of the M1 thumb award...

    @75ft I can't imagine not running power from house. I just did just that couple of weeks ago. 10awg works for most everything short of industrial welder or such. Ran romex plus a single thhn wire for neutral as its much cheaper than 10/3 romex. Main panel is using 30 amp bkr while shop has no main but is only 6 slots.
    3 slots 20 amp bkr (small heater and two plug circuits) and two slots for lighting ckts leaving one spare. Put it all into 1 inch pvc (3/4 ok) buried 18 inches underground. All in all was pretty cheap material wise.... located in SW coast of Oregon so sand is easy digging!
    I've been solar since 1999 but when grid is available so close it's the better option.
    If you want solar go to a 2000 watt or bigger grid tie system! Payback is quicker and prices have dropped a bunch since my latest installation....
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