Rule 21 Grid Standard Guide

The California Energy Commission (CEC) provides a list of every "Rule 21 Compliant" inverter that is available for purchase. This list can be found here:

Solis inverters are listed under the manufacturer name "Ginlong Technologies Co., Ltd."

By setting the inverter to a Rule 21 grid standard, you are ensuring that the inverter will operate according to the definitions within Rule 21. Below are guides for how to both enable and disable the Rule 21 grid standard. At the bottom is the guide for how to verify which grid standard your Solis inverter is currently set to. 

Enabling the Rule 21 grid standard:

  • From the main screen press Enter, then press Up once to highlight "Advanced Settings", then press enter again
  • The password is 0010 - press Down, Down, Up, and then Enter
  • Highlight Standard Select, but it should be already highlighted as it is the first option - press Enter
  • If "R21P3-240"  or "R21P3-24A" is displayed, then the inverter is already set to the Rule 21 grid standard 
    • Please note: "R21P3-24A" is Rule 21 with AFCI enabled; whereas "R21P3-240" is Rule 21 without AFCI enabled
  • If a different grid standard is shown, use the Up and Down buttons to scroll through the various grid standard options that are available. All of the Rule 21 standards start out like this: "R21P3" for Rule 21 Phase 3 (note: not 3-phase, but Phase 3 of Rule 21)
  • Single-phase Solis inverters should be set to either: R21P3-24A or R21P3-240 (R21P3-24A if AFCI is required)
  • Three-phase Solis inverters should be set to either: R21P3-48A or R21PR-480 (R21P3-48A if AFCI is required)
  • Three-phase utility-scale inverters (600-800 Vac) should be set to either: R21P3-600 or R21P3-60A
  • With the R21P3 grid standard highlighted, press Enter then Escape - Save and Send will be displayed, press Enter
  • The Rule 21 grid standard has now been set

Verifying the working mode:

  • With a Rule 21 grid standard set, the working mode should be adjusted automatically 
  • Go to Advanced Settings > Std. Mode Set >Working Mode - press Enter

Disabling the Rule 21 grid standard: 

Solis technical support specialists have observed that many installers are not verifying that the grid standard is set according to their local utility standard.  California Rule 21 is not required in every authority having jurisdiction (AHJ). 

Solis inverters come with the Rule 21 grid standard set as default.  For installations outside of R21 territory, the failure to change to the UL standard and disable associated standard modes per the manual can lead to reduced power output and the need for additional site visits to set the standards correctly.



Inverters with Rule 21 grid standard as default also have Rule 21 work modes set.  If the grid standard is changed to an IEEE 1547 standard like UL-240V-A, the R21 work modes must also be disabled in accordance with the product manual.

  • Go to Advanced Settings > Std. Mode Set > Working Mode > make sure this is set to "NULL"
  • If this is not set to NULL, use the Up and Down buttons to highlight NULL and then press Enter

Procedure for verifying the grid standard 

Step 1: Verify Grid Standard is Set Correctly

  1. Enter the Advanced Settings Menu: Advanced Settings -> Password: 0-0-1-0 -> ENTER
  2. Turn off the AC power to the inverter: Grid On/Off -> Select "Off"-> ESC. This brings you back to the Advanced Settings Menu.
  3. Next, verify that the grid standard currently selected matches your local AHJ requirements.  Outside of California, for single phase systems this will typically be UL-240V-A, UL-208V-A, ISONE240A, or ISONE208A.
  4. Scroll through the list of grid standards, and select the correct standard for your area.  Then, Save & Send.
  5. Leave the Grid “OFF” and proceed to Step 2.

Step 2: Verify Advanced Settings Correspond with the Selected Grid Standard

  1. If you are not using one of the Rule 21 (R21) grid standards, verify that all the settings associated with R21 are inactive.  Under Advanced Settings -> STD. Mode Settings:
    1. Working Mode Set -> Select "NULL"
    2. Freq Derate Set -> Select “Mode 00”
    3. Freq-Watt -> Select “Hysteresis: Disable”
  2. ESC from STD. Mode Settings, but remain in Advanced Settings menu.

Step 3: Restore AC Power to Verify Normal Operation

  1. Advanced Settings -> Grid On/Off -> Select "ON"-> ESC.
  2. Observe inverter and verify normal operation.
  3. If you experience continued operation problems, notify Ginlong Solis USA technical support via 1-866-438-8408 or
Victor is the author of this solution article.

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