XW6048 Backfeed via AC load port

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Ken Marsh
Ken Marsh Solar Expert Posts: 114 ✭✭✭✭
Hello guys,

I am a new neighbor on the block.
I surfed in a couple months ago and have spent quite a little time reading.
Great board with lots of good info.
You are to be complimented for keeping it congenial and useful this long.

Here is a situation that is bugging me right now. I would appreciate your input.
Is a Xantrex XW6048 inverter capable of back feeding the grid from its AC load terminals?

Normally in grid tie situations the tie is done through the grid (AC1) connection.
The grid feed is done after a qualification period after which the inverter then syncs to the grid.
But with the AC load connection there is nothing to sync to hence the inverter would have to be doing its own clocking. It seems like this would make it incapable of back feeding.

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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
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    Re: XW6048 Backfeed via AC load port

    Not quite sure what you mean. The AC1 in (grid AC) is not the same as the AC Load output. For grid tie you need to have the AC1 grid terminals tied to an active grid.
  • Ken Marsh
    Ken Marsh Solar Expert Posts: 114 ✭✭✭✭
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    Re: XW6048 Backfeed via AC load port

    Thanks for reply Windsun,

    "The AC1 in (grid AC) is not the same as the AC Load output. For grid tie you need to have the AC1 grid terminals tied to an active grid."

    That is the point. I am using only the AC load output in a non-grid connect system. Yet the power Co. thinks I am back feeding.

    And while you are here, how do you add a signature line to a post?
    I would like to put a system description up like the rest of the guys have but have not been able to get it to go.
    That is an interesting feature of this board.

    Km
  • BB.
    BB. Super Moderators, Administrators Posts: 33,500 admin
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    Re: XW6048 Backfeed via AC load port

    Welcome to the forum Ken,

    We do have our moments though:roll:.

    Regarding signatures:

    • Upper right "Settings"
    • Middle left "Edit Signature"
    • [remove this step, wrong click box--See next stop]
    • Last step, below the "ADVANCED edit post" window, there is a click box with "Show Your Signature". Click once, and it stays for ever more. [you actually have to make a "new post" or edit and existing post to get the "click box" for show your signature]

    The utility may be looking at the panels on your roof and the reduction in your power bill. Did you get/need a building permit/inspection for your installation?

    Do you use the AC1 Grid Connection for charging the battery bank? The XW Hybrid Inverter is configurable for GT operation or not.

    In California, it is illegal for us to even install an off grid power system in our home without paying "stranding charges" to the Utility under the theory that the Utility has taken out 40 year bonds and made investments "in my name" to supply power well into the future. To leave/off set the grid power they planned/committed me to use, I have to pay them back for that investment.

    Small (10kW or smaller) solar RE systems are specifically allowed to (temporarily?) avoid paying the "leave the grid" charge.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Joe_B
    Joe_B Solar Expert Posts: 318 ✭✭✭✭✭✭
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    Re: XW6048 Backfeed via AC load port

    If you are grid tied and you dont want to backfeed the grid, make sure SELL mode is disabled.
  • Ken Marsh
    Ken Marsh Solar Expert Posts: 114 ✭✭✭✭
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    Re: XW6048 Backfeed via AC load port

    The system is not permitted.
    This has been going on for quite a while but I did put the PVs up on the roof last year to get them away from the farm traffic.
    When the leaves are off you can see them from the road.

    There is no connection to the inverter's "AC1 Grid" terminals.
    If I want to charge bats from the line I use a different charger.

    Off hand, at the moment I do not know if "sell" mode is off
    but I don't think it makes any difference when you have no AC1 connection.

    Km
  • BB.
    BB. Super Moderators, Administrators Posts: 33,500 admin
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    Re: XW6048 Backfeed via AC load port

    Ken,

    Sorry--that 3rd step was to see other people's signatures (I think). You need to do this to make your signature visible:
    Last step, below the "ADVANCED edit post" window, there is a click box with "Show Your Signature". Click once, and it stays for ever more. [you actually have to make a "new post" or edit and existing post to get the "click box" for show your signature]

    I have added a temporary signature to your account and enabled your signature for all posts now.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Ken Marsh
    Ken Marsh Solar Expert Posts: 114 ✭✭✭✭
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    Re: XW6048 Backfeed via AC load port

    OK, will see if signature works from here.
    Evidently you have to be in "Advanced Edit" to turn on "Show Signature".
    Now the "Show Signature" check box is just below this window.

    Many thanks for the help.

    Km
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
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    Re: XW6048 Backfeed via AC load port

    Perhaps a simplied diagram and explaination on XW inverter works may help you.

    See the attached diagram.

    Each voltage and current sense produces a small AC signal going to controller board that represents the magnitude and phase of its respective measurement point. This allows absolute voltage, current, and power flow direction to be measured by the controller.

    The inverter part (transformer output) is bi-directional. By adjusting its high frequency PWM signal it can produce a 60 Hz sinewave with a voltage within the boundary limits of maximum and minimum line voltage allowed. It can also be turned off (standby) producing no output (or charging input) while controller keeps sync timing with any ACin voltage so it can immediately come on line, in sync with ACin voltage.

    First thing that happens when an ACin appears is the controller will gradually slew the inverter's phase and voltage alignment to match the ACin source. Assuming the ACin is within voltage and frequency limits set, the respective ACin relay will then close putting the inverter in parallel with the ACin source.

    When you set inverter to disable selling, all this means it the voltage/current sense on ACin port will not allow the inverter to push any power out the AC1in port. A power company may be nervous about seeing an ACin connection to their grid even though the XW software will prevent a backpush into the grid.

    If you backfeed (called AC coupling) from a GT inverter into ACout port, and have no ACin connected to grid (or its breaker open), any backfeed power into ACout will go to battery. There is no charge current limiting in this mode so if your GT produces 5kW then 5kW will be pushed to battery. If battery voltage rises to charge voltage limit the XW will slew its frequency until GT inverter goes out of its relatively tight frequency limit causing GT inverter to shut down. In this mode the XW is the frequency/voltage master for the GT inverter connected to ACout port.

    When grid is connected via ACin1, inverter is sync'd with relay AC1 engaged, and selling is enabled, any backfed power from a GT inverter connected to ACout will backflow into grid. It may also suck off some of the backfed power to charge battery if set to do so. In this mode the grid is frequency/voltage master.