Off-Grid cabin, connecting charger/inverter to main panel.

Egyas
Egyas Registered Users Posts: 2 ✭
in Off Grid Solar & Battery Systems #1
I have a small off-grid cabin, and I need some assistance w/ the wiring.  I'm competent at basic wiring, but this part of the project is a bit more than I thought it would be, and I want to make sure I'm doing it safely.

Set-up.
Charger/Inverter: SkyMax Stratus 24 Volt 4000 
Batteries: MIGHTY MAX 12-Volt 100 Ah Rechargeable Sealed Lead Acid Battery

I have 10 12v 100mAh batteries that will be wired (series) into 24v cells, so I'll end up w/ 5 24v cells wired in parallel.  These are connected to the Charger/inverter, which will be connected to the Electrical panel in the house.

The house is wired in standard fashion for 100A service following electrical code.  This set-up is 100% off-grid, and will never be tied into the grid.  In fact, it's impossible to get grid-power there.

Eventually I'll have the solar array up and running, but for now (cost reasons) we're running entirely off generator.  The plan (for now) is to use the generator to power the cabin and charge the batteries until they are full, then have the charger/inverter draw from the batteries to power the house once the genny is off.

So here's my sticking point.  I need to do the actual connection from the charger/inverter to my main panel.  I'm wondering what gauge/type of wire is proper.  I have read that for a standard residence they would use 4 AWG or 3 AWG wire to connect the meter to the panel.  But I'm unsure if this is still the proper wire to use from the inverter to the panel as well?

The Charger/Inverter came w/ a user manual that is rather "slim".  Great on the operation details, but totally lacking on the wiring details.,  Probably because if you're doing this, you're supposed to know what the heck you're doing already.  ;)

Here is a pic of the bottom of the Inverter/Charger for reference.


Here's a pic of the side panel label on the Charger/Inverter.

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Comments

  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    I'm not familiar with the brand, but 4000 watts over a single leg would be 4000/110= 37 amps.  
    NEC chart apears many 10 gauge wires would be fine;
    Ampacity Table 31015B16
    I left mine at 10 gauge when installing my new 3500 watt inverter, Magnum 4024.

    Wiring from the battery bank will need to be quite large. 4400 watts / 24=183 amps
    What is wire ampacity and how do you find ampacity rating

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • checkthisout
    checkthisout Registered Users Posts: 31 ✭✭
    edited December 2021 #3
    Use 8 gauge stranded copper. 

    Edit: Nevermind. That 2kw per leg. 10 gauge is overkill. Do still use stranded wire. I hate those connector blocks. My inverter uses those same ones. You need a thin screwdriver that will just about bend the blade before you achieve the right torque. Stranded wire conforms to that type of connector better.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
    If you still have the chance, exchange the inverter for a 48V model.   Half the DC amps, better load balance for the batteries, with fewer parallel strings.

    Stranded or solid wire - inside the wire block, does the setscrew auger into the wire, or does it press a metal plate that clamps the wire ?
    Setscrews that auger into the wire work poorly with stranded wire, the strands allow the screw point to slide right by, without much grip.
     The inverter manual should specify what style of wire to use, and the proper torque.
    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: 33,613 admin
    #5
    There is also the issue of standard (coarse) stranded wire (electrical wiring) and fine stranded wire (welding cables, diesel electric locomotives, etc. where there is lots of movement and vibration).

    Typically fine stranded cable needs "clamps"/crimps that are designed for this type of cable.

    Fine strands tend to "squirm out of" typical clamps/holding screws designed for solid or coarse stranded cables.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • checkthisout
    checkthisout Registered Users Posts: 31 ✭✭
    #6
    The connector block is the same on both sides. I know they aren't using solid wire to attach to the circuit board.
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  • Saggys
    Saggys Solar Expert Posts: 189 ✭✭✭
    #7
    What size wire will your 100 amp house panel accept? 10 AWG may not be acceptable for your house panel lugs (too small). That may determine your wire size.
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  • Egyas
    Egyas Registered Users Posts: 2 ✭
    edited December 2021 #8
    Saggys said:
    What size wire will your 100 amp house panel accept? 10 AWG may not be acceptable for your house panel lugs (too small). That may determine your wire size.
    Just got done looking at the breaker/main panel again.  For those connectors the label in the panel specified 4 AWG wire.  I'm a bit worried that the wire is simply too large for that inverter.

    I have a call into the retailer.  The silly little 16 page "user's manual" repeatedly says "Refer to the installation section...", but there is no installation section.  I'm hoping that I'm just missing a booklet.  Sadly the manufacturer's website is crap.
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  • checkthisout
    checkthisout Registered Users Posts: 31 ✭✭
    #9
    Egyas said:
    Saggys said:
    What size wire will your 100 amp house panel accept? 10 AWG may not be acceptable for your house panel lugs (too small). That may determine your wire size.
    Just got done looking at the breaker/main panel again.  For those connectors the label in the panel specified 4 AWG wire.  I'm a bit worried that the wire is simply too large for that inverter.

    I have a call into the retailer.  The silly little 16 page "user's manual" repeatedly says "Refer to the installation section...", but there is no installation section.  I'm hoping that I'm just missing a booklet.  Sadly the manufacturer's website is crap.
    Do you have to pass some sort of inspection?

    Just put whatever gauge wire your inverter takes into the 4 gauge clamps in the panel. If it holds, it holds. I assume you are using copper from the inverter to the panel. 

    If you're not comfortable doing that then just back feed the panel with a standard breaker of suitable size. 
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