Understanding "LimByVg" Operating Status

The operating status “LimByVg” means “Limited by Grid Voltage,” and does not indicate a problem with inverter operation.  This operating mode is activated to curtail inverter power output when grid voltage rises beyond a specified amount. This only occurs when the inverter’s grid standard is set to Rule 21 (California only) or when “Volt-Watt” mode has been activated in the Advanced Settings -> Standard Mode Settings submenu.


If your AHJ does not require your inverter to operate under Rule 21, the work modes that result in "LimByVg" can be disabled through the following path:

Step 1: Verify Grid Standard is Set Correctly

  1. Advanced Settings -> Password: 0-0-1-0 --> Select Standard
  2. Verify that the grid standard currently selected matches your local AHJ requirements.  Outside of California, this will typically be UL-240-A, UL-208-A, UL-480-A, or ISO-NE.
  3. If the grid standard is not set correctly, turn off the AC power to the inverter (either via the AC switch, or via Advanced Settings --> Password: 0-0-1-0 --> Grid On/Off --> Grid "Off."
  4. Scroll through the list of grid standards, and select the correct standard for your area.  Then, Save & Send.
  5. Next, in Advanced Settings, scroll down and select STD. Mode Settings --> Work Mode.  Set to "NULL" if not already selected.
  6. Restore AC power to the inverter.  If AC switch was turned off, turn off DC power, then switch AC, then DC back on.  If AC turned off via Advanced Settings --> Grid On/Off, select Grid "On."
  7. Observe unit functioning and verify correct operation.


What if I am required to use a Rule 21 Grid Standard, but don't like power curtailment from LimByVg?

LimByVg is actually a very useful feature, and will result in improved production and reliability over the long term.  By entering “LimByVg” mode when higher-than-usual grid voltage is detected, the inverter is able to continue operating and producing power during times when it may otherwise enter into a “Grid Overvoltage” fault (OV-G-V) and stop producing altogether. As soon as the high grid voltage decreases, the inverter resumes full power output without any interruption. This is the best-case scenario for your production, and for grid stability!


If you observe your inverter remaining in “LimByVg” mode for long periods of time, contact your installer. It could indicate an issue with either the inverter or the local utility grid.


Note: If the inverter is not able to sufficiently decrease the grid voltage by operating in "LimByVg," it will still protect itself and your property through its usual mechanism by going into a Grid Overvoltage fault state, which resolves on its own when the grid voltage returns to normal range.

J
John is the author of this solution article.

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