FAQ.md

@@ -26,7 +26,7 @@
 * **Sometimes my results are not updated even though I have changed the input file and run backbone again.**
     * In the option files of VTT in 1_options.gms behind gdxxrw (this is the tool which converts xlsx into gdx) the parameter CheckDate is located. This ensures that the inputData.gdx is only rewritten if it is older than your input file. Sometimes there can be problems with the "last used" timestamps and inputData.gdx is not rewritten. You can either remove the inputData.gdx manually or remove the CheckDate parameter in 1_options.gms.
 * **I want to "force" a (thermal) unit to run for the whole time.**
-    * create a group (sheet: group); assign all n units that "must run" to the group (uGroup); set constrainedOnlineTotalMax = -n (p_groupPolicy); for each unit (column *), set constrainedOnlineMultiplier=-1 (p_groupPolicy3D)
+    * create a group (sheet: group); assign all n units that "must run" to the group (uGroup); set constrainedOnlineTotalMax = -n (p_groupPolicy); for each unit (column *), set constrainedOnlineMultiplier=-1 (p_groupPolicy3D). For this you cannot use the efficiency approximation "directOff" as no online variable exists is that case.
 * **I want to include a parameter in my input file that is not included in the example, so I don´t know where to put it.**
     * Search the backbone code for the parameter name and you will see from where it is read. You can for example search the backbone/inc folder using VS Code´s "find in folder" or search the Backbone.lst file from your last run using GAMS Studio.
 * **That p_gnu_io sheet doesn´t really make sense to me.**