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Thread: Best way to wire in inverter to breaker panel?

  1. #1

    Default Best way to wire in inverter to breaker panel?

    I'm looking to wire my inverter to my panel. Should I wire to the panel first lug with a jumper to the second lug or can I take a 30 amp double pole breaker and put a jumper on the breaker to power both sides of panel?

    Other info:
    Offgrid cabin no utilities
    Vanner 2600 watt inverter
    Square D panel
    All 120 volt no 240

  2. #2
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    Default Re: Best way to wire in inverter to breaker panel?

    I am a bit confused...

    Assuming this is an off grid system, you treat the battery as the "heart" of your system.

    The solar panels go to the solar charge controller which then connects to the battery +/- Bus.

    Then your off grid inverter connects its cables to the battery +/- Bus.

    Normally, you would have fuses/circuit breakers/switches, as needed, between each of the devices and the +/- battery bus.

    Only a Grid Tied Inverter would connect directly to the solar panels (Grid tied inverter+solar panels, no battery bank). A GT Inverter is then connected to your utility panel which eventually connects to your utility meter and power grid and cannot operate if there is no grid or if the utility power failed (as during a storm, power pole knocked down, etc.).

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  3. #3

    Default Re: Best way to wire in inverter to breaker panel?

    I'm wanting to wire the inverter ac output to the square d load center ( breaker panel). Click image for larger version. 

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  4. #4

    Default Re: Best way to wire in inverter to breaker panel?

    Click image for larger version. 

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    Like this or using that double pole breaker with a jumper on the breaker instead of the panel lugs to act as a main breaker if possible?

  5. #5
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    Default Re: Best way to wire in inverter to breaker panel?

    Oh--OK.

    Several questions first... What Brand/model of AC inverter do you have?

    Most MSW inverters cannot have their output connected to earth/green wire/bonded to neutral grounding (if battery is also negative or positive grounded too). This creates a short circuit through "most" MSW inverters and will let the magic smoke out.

    And most TSW inverters have fully isolated AC outputs--So you can take one of the AC outputs, put a white wire on it, and connect it to the neutral/ground bus in the main panel. And the black wire output can connect to the bus bar/main breaker in the AC panel.

    You need to read the manual for your AC inverter and grounding to ensure you do not make a costly mistake.

    If the main panel's AC Current rating is equal too, or less than the AC inverter's maximum output current rating, then you can jumper both buses together so you can have 2x as many breaker positions for a 120 VAC only panel.

    Make sure you "home run" each black wire out and white wire back to the main panel. You don't want to send out two "hot wires" and bring back one white wire as you would normally do with typical north American home's 120/240 VAC Split Phase power.

    With two "black" phases from a 120 VAC only panel, the current from both hots add up and can overheat the neutral/return wire.

    With 120/240, the neutral is the center tap of a transformer and will never carry more current than that of either of the hot wires.

    Sorry--it is confusing to write this--and doubly hard to read and make sense not knowing your experience level with 120 vs 120/240 VAC circuits.

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  6. #6
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    Default Re: Best way to wire in inverter to breaker panel?

    Yes, you can attach to the lugs, or use the double pole breaker as a "main breaker" (assuming it is rated for the maximum current you wish to use from your AC inverter).

    If your AC inverter's output current is equal to, or less than, the bus bar ratings, you are not really making anything safer. Just adding a convenient way to turn of AC power to your loads by throwing "one switch".

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  7. #7

    Default Re: Best way to wire in inverter to breaker panel?

    It's a vanner bravo 2600sh 12 volt no charger. They call it quasi sine wave which i beleive is modified. I have it hooked to the batteries and batteries are hooked to an iota iq4 55 amp charger with a positive and a negative cable. I have the charger ground hooked to an earth grounding rod.
    http://www.vanner.com/wp-content/upl...M-D96397-A.pdf

    This is the load center I have.
    http://m.homedepot.com/p/Square-D-by...ack/202529821/
    Attached Images Attached Images  

  8. #8

    Default Re: Best way to wire in inverter to breaker panel?

    I will add I'm just in the beginning phases and collecting things as I go. I put the batteries on the chopped up jumper cables as a temporary thing to keep them charged while I figure all this out. Next will be a charge controller and a solar panel to keep them from freezing. Looking at a xantrex xw 60 and one 235 watt panel to start. Its going to all be set up in Alaska and I can only get there by float plane or snowmachine at a remote recreational cabin.

  9. #9
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    Default Re: Best way to wire in inverter to breaker panel?

    First note: Do not use battery clamps for connecting up your inverter's DC input power. Bolt everything together. Battery clamps typically do not make "good enough" electrical connections to reliably pass the current for a largish AC Inverter:

    2,600 Watt inverter * 1/0.85 inverter eff * 1/10.5 volts battery cutoff * 1.25 NEC wiring/breaker derating = 364 Amp branch circuit recommendation

    >300 amps is a lot of current to pass through anything but solid "bolt up" connections and very heavy copper wiring.

    Back to the type of inverter question:

    It is a MSW inverter, and they completely skip talking about AC Neutral Bonding (or not).

    It may have a transfer switch--two pole would be my assumption--so the neutral is bonded to ground by the utility panel, but is not bonded if the inverter is operating and powering the main panel.

    So--in your main panel, being completely off grid operation (?)--Your AC panel needs to have an isolated "neutral/white" wire power block (it looks like you can float it fro ground by cutting/lifting the bonding strap on the left of the bus bar.

    So, bring the "black wire" from the inverter to your AC bus bars (jumpered together if you wish). And the "white wire" to the, now floating, return bus.

    And wire up the rest of your system.

    Note, if you ground bond the battery negative terminal with the rest of your grounding (inverter ground is probably just to the metal shell of the inverter and the metal box of the battery charger), this would be the "standard" method for DC grounding your system. Then you can put fuses in the positive bus connections to your inverter, battery charger, etc....

    The following is an "advanced discussion" about grounding MSW inverters. There are lots of grounding/wiring issues with MSW inverters and how we "normally" connect AC and DC wiring. You can ignore this part just like 99.999% of the people do. However, if you are very concerned about (fire) safety, then you can read/discuss the following:

    But the AC Inverter wires are now not floating (if the battery bus is grounded)--And if you accidentally short to ground either of the inverters Black OR WHITE wires, it can cause excessive current to flow and smoke wiring and/or AC inverter--so both inverter's outputs should be protected by a fuse or breaker.

    In reality, you should treat the MSW Inverter's output like 120/240 VAC wiring. Each branch wiring should go through a pair of ganged breakers to cut of the power if either wire gets over current (as from a short to ground or hot to hot short). And not even use the return bus connection (except for green wire grounding--if needed).

    If you do not ground reference the Battery Bus--Then both the Battery's DC Bus and Inverter's AC outputs are floating with respect to ground (more or less)--which is very commonly done to reduce the chance of a short circuit causing problems.

    Still not "safe" from an NEC/Engineering sense, but very typical for such MSW inverter installations.

    Floating power systems should have double pole/ganged breakers on their output wiring to protect both sides from shorts. If the return is grounded, then the ground referenced return wiring generally will not ever have any voltage above ground, so a return wire to ground short will not create excessive current, and does not need fusing.

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  10. #10
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    Default Re: Best way to wire in inverter to breaker panel?

    By the way, what are the AH ratings (we use 20 Hour rate for our rules of thumb) of those cells?

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

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