New Off-Grid Installation Questions

3bhlives3bhlives Registered Users Posts: 4
Hi,

I am about to install my first small off-grid system at my cabin (minus the solar panels), and have a few questions. My system will consist of the following:

- Champion 2000W inverter generator
- 2 6V deep cycle batteries wired in series
- Xantrex Freedom HF 1000 inverter/charger (for RV and marine)
- AC load center

I plan to wire up my system as follows:

- connect my batteries to the inverter with #2 wire (80A fuse and 200A+ battery disconnect switch off the positive)
- connect external male outlet to the AC input with 12/2 wire (will plug in and start generator to charge batteries and run high load appliances - microwave, vacuum, etc. - fridge and stove are propane)
- connect AC output to load center with 12/2 wire (note: cabin is wired with 14/2 wire throughout)
- ground inverter with 30' of #2 bare and a grounding plate

My questions are as follows:

- if the only AC source is from my generator (with built in breakers), do I need a fuse/breaker between the external male outlet and the inverter AC input?
- my manual states that my generator must have its neutral bonded to ground. does anyone know if this is the case for my generator? I can't find any literature for it. the generator states floating neutral on it. there's also a nut that apears to have a ground symbol beside it. does this mean I have to connect my generator to a ground?
- on the same note as above, my manual also states that the neutral conductor of the invertor's AC output circuit (i.e., AC Output Neutral) is automatically connected to the safety ground during invertor operation. when the AC utility power is present (generator) and the inverter is charging the batteries, this connection is not present, so that the utility neutral (i.e., AC Input Neutral) is only connected to the utility ground. so if my generator is not bonded to ground, does that mean I have no ground? if this is the case, does anyone have a fix?
- last question. I have not purchased a load center yet. I only have 4 circuits (small system) and it appears that the smaller load centers are sub panels (i.e., main lug). does anyone know if I need a main breaker panel, or can I wire my inverter directly to a main lug? If I need a main breaker load center, does anyone know of a small main breaker load center?

PS. while searching the forum, I found some info on a post that made me very nervous. see "inverter/charger + generator = SMOKE!" post.

Thank you and cheers.

Comments

  • CariboocootCariboocoot ✭✭ Banned Posts: 17,615 ✭✭
    Re: New Off-Grid Installation Questions

    Welcome to the forum.

    If the generator's output has a breaker on it (all the Champion's I've seen do) and the wire is sized properly (14 AWG as the gen outlets are 15 Amp) you would not need an additional fuse or breaker on this circuit.

    Generator has floating neutral = no N-G bond on the generator. If the inverter manual says it should have one, then the inverter's transfer switch lifts its N-G bond when AC is supplied externally. This is common for marine applications where the external AC would be 'shore power'; standard electric service with N-G bond included. It's how it avoids having two bonds on the system. The grounding lug (nut with ground symbol on it) is where the ground wire attaches, but this does not create an N-G bond it just grounds the generator chassis. You will need to create one in the wiring between the gen and inverter.

    The output of the inverter is very low power. You don't actually need a breaker panel for multiple AC circuits unless you are planning on expanding to a larger inverter later. The inverter will fault before a breaker trips. My 3.5 kW inverter will fault before a breaker trips. Sub panels & breakers serve only as a convenient method of distribution. You do not need a 'main breaker' before any circuit branching. At 1 kW you have 'less than one outlet's worth' of power; treat it like a single 15 Amp circuit (8 Amps really).

    And yes it is unfortunately easy to mis-wire these systems and let the magic smoke out. One way to do it right, a million ways to do it wrong. The odds are against us all!
  • 3bhlives3bhlives Registered Users Posts: 4
    Re: New Off-Grid Installation Questions

    Hi Cariboocoot,

    Thanks for the information. This is what I understand...correct?

    - No need for additional fuse/breaker
    - Need N-G bond on Gen.
    - Main lug fine.

    This N-G bond is confusing, but I think I'm starting to understand. Any ideas on how to create the N-G bond in the wiring between the Gen and inverter? And, do I need to ground my Gen?

    Thanks again.
  • CariboocootCariboocoot ✭✭ Banned Posts: 17,615 ✭✭
    Re: New Off-Grid Installation Questions
    3bhlives wrote: »
    Hi Cariboocoot,

    Thanks for the information. This is what I understand...correct?

    - No need for additional fuse/breaker
    - Need N-G bond on Gen.
    - Main lug fine.

    This N-G bond is confusing, but I think I'm starting to understand. Any ideas on how to create the N-G bond in the wiring between the Gen and inverter? And, do I need to ground my Gen?

    Thanks again.

    No, you don't need any additional fuse/breaker on the line from the gen to the inverter.
    Yes, you need to ground the generator.
    The N-G bond for it is simple to create; just make the connection in the cable between gen and inverter. When it is unplugged the 'extra' bond will be irrelevant to the inverter because there will be no circuit on that line. Basically you will be making the inverter N-G bond permanent.
  • 3bhlives3bhlives Registered Users Posts: 4
    Re: New Off-Grid Installation Questions

    Thanks again.

    So just to confirm, you are saying to jump the N to G somewhere between the Gen and Inverter? Below is my proposed system. I've clouded what I think your saying.

    One last question. Can I ground my Gen to the DC ground?

    Cheers
    Attachment not found.
  • CariboocootCariboocoot ✭✭ Banned Posts: 17,615 ✭✭
    Re: New Off-Grid Installation Questions

    That's correct.
    Connecting neutral to ground on the inverter's AC in line basically making the bond there permanent (not lifted when AC in is sensed).
    All grounds, including DC negative, should go to the same ground rod.
  • AuricTechAuricTech ✭✭ Solar Expert Posts: 140 ✭✭
    Re: New Off-Grid Installation Questions

    If the price premium isn't a show-stopper, I suggest you look into a pure sine wave (PSW) inverter/charger, such as the Magnum MMS1012 inverter/charger (not listed on our host's Web site; the smallest Magnum PSW inverter/charger NAWS lists is the MS2012 2000W inverter/charger). A quick Internet search indicates that the going price for the MMS1012 is about $960.
  • CariboocootCariboocoot ✭✭ Banned Posts: 17,615 ✭✭
    Re: New Off-Grid Installation Questions

    I agree that a pure sine inverter (Xantrex Prosine for example) would be better.
    But at least this one is good enough to allow Neutral-ground bonding; many of the MSW inverters go up in smoke if you do that.
  • 3bhlives3bhlives Registered Users Posts: 4
    Re: New Off-Grid Installation Questions

    Thank you. Very much appreciated.:D

    Cheers!
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