Check for zero airflow. Update Changelog.md.

Changelog.md

@@ -2,6 +2,8 @@
 
 __New Features__
 - Adds inputs for modeling skylight curbs and/or shafts.
+- Central Fan Integrated Supply (CFIS) mechanical ventilation enhancements:
+  - Allows modeling systems with no strategy to meet remainder of ventilation target (`CFISControls/AdditionalRuntimeOperatingMode="none"`).
 - HVAC Manual J design load and sizing calculations:
   - Adds optional inputs and outputs for blower fan heat and piping load.
   - Miscellaneous improvements.

HPXMLtoOpenStudio/measure.xml

@@ -3,8 +3,8 @@
   <schema_version>3.1</schema_version>
   <name>hpxm_lto_openstudio</name>
   <uid>b1543b30-9465-45ff-ba04-1d1f85e763bc</uid>
-  <version_id>191a94c7-3844-4cdc-a63c-6c7da5d4b254</version_id>
-  <version_modified>2024-07-02T21:09:24Z</version_modified>
+  <version_id>c249bd31-bb0e-49dd-9d2a-8a16e89b7d76</version_id>
+  <version_modified>2024-07-02T21:37:44Z</version_modified>
   <xml_checksum>D8922A73</xml_checksum>
   <class_name>HPXMLtoOpenStudio</class_name>
   <display_name>HPXML to OpenStudio Translator</display_name>
@@ -189,7 +189,7 @@
       <filename>airflow.rb</filename>
       <filetype>rb</filetype>
       <usage_type>resource</usage_type>
-      <checksum>71427533</checksum>
+      <checksum>8BAD739B</checksum>
     </file>
     <file>
       <filename>battery.rb</filename>

HPXMLtoOpenStudio/resources/airflow.rb

@@ -1750,8 +1750,12 @@ def self.apply_cfis(infil_program, vent_mech_fans, cfis_fan_actuator, cfis_suppl
           @runner.registerWarning("CFIS supplemental fan '#{vent_mech.cfis_supplemental_fan.id}' is undersized (#{vent_mech.cfis_supplemental_fan.oa_unit_flow_rate} cfm) compared to the target hourly ventilation rate (#{vent_mech.average_total_unit_flow_rate} cfm).")
         end
         infil_program.addLine("    Set cfis_suppl_Q_oa = #{UnitConversions.convert(vent_mech.cfis_supplemental_fan.oa_unit_flow_rate, 'cfm', 'm^3/s')}")
-        infil_program.addLine("    Set cfis_suppl_f = #{@cfis_f_damper_extra_open_var[vent_mech.id].name} / (cfis_suppl_Q_oa / cfis_Q_duct_oa)") # Calculate desired runtime for supplemental fan to provide remaining ventilation requirement
-        infil_program.addLine('    Set cfis_suppl_f = @Min cfis_suppl_f 1.0') # Ensure desired runtime does not exceed 100% (if the supplemental fan is undersized)
+        if vent_mech.cfis_supplemental_fan.oa_unit_flow_rate > 0
+          infil_program.addLine("    Set cfis_suppl_f = #{@cfis_f_damper_extra_open_var[vent_mech.id].name} / (cfis_suppl_Q_oa / cfis_Q_duct_oa)") # Calculate desired runtime for supplemental fan to provide remaining ventilation requirement
+          infil_program.addLine('    Set cfis_suppl_f = @Min cfis_suppl_f 1.0') # Ensure desired runtime does not exceed 100% (if the supplemental fan is undersized)
+        else
+          infil_program.addLine('    Set cfis_suppl_f = 0.0')
+        end
         infil_program.addLine("    Set cfis_suppl_fan_w = #{vent_mech.cfis_supplemental_fan.unit_fan_power}") # W
         infil_program.addLine("    Set #{cfis_suppl_fan_actuator.name} = #{cfis_suppl_fan_actuator.name} + cfis_suppl_fan_w * cfis_suppl_f")
         if vent_mech.cfis_supplemental_fan.fan_type == HPXML::MechVentTypeSupply