Standards.AirLoopHVAC.rb in openstudio-standards-0.2.12.rc1

- old
+ new

@@ -400,10 +400,12 @@
 
     # TODO: determine the presence of MERV filters and other stuff
     # in Table 6.5.3.1.1B
     # perhaps need to extend AirLoopHVAC data model
     has_fully_ducted_return_and_or_exhaust_air_systems = false
+    has_MERV_9_through_12 = false
+    has_MERV_13_through_15 = false
 
     # Calculate Fan Power Limitation Pressure Drop Adjustment (in wc)
     fan_pwr_adjustment_in_wc = 0
 
     # Fully ducted return and/or exhaust air systems
@@ -411,10 +413,24 @@
       adj_in_wc = 0.5
       fan_pwr_adjustment_in_wc += adj_in_wc
       OpenStudio.logFree(OpenStudio::Info, 'openstudio.standards.AirLoopHVAC', "--Added #{adj_in_wc} in wc for Fully ducted return and/or exhaust air systems")
     end
 
+    # MERV 9 through 12
+    if has_MERV_9_through_12
+      adj_in_wc = 0.5
+      fan_pwr_adjustment_in_wc += adj_in_wc
+      OpenStudio.logFree(OpenStudio::Info, 'openstudio.standards.AirLoopHVAC', "--Added #{adj_in_wc} in wc for Particulate Filtration Credit: MERV 9 through 12")
+    end
+
+    # MERV 13 through 15
+    if has_MERV_13_through_15
+      adj_in_wc = 0.9
+      fan_pwr_adjustment_in_wc += adj_in_wc
+      OpenStudio.logFree(OpenStudio::Info, 'openstudio.standards.AirLoopHVAC', "--Added #{adj_in_wc} in wc for Particulate Filtration Credit: MERV 13 through 15")
+    end
+
     # Convert the pressure drop adjustment to brake horsepower (bhp)
     # assuming that all supply air passes through all devices
     fan_pwr_adjustment_bhp = fan_pwr_adjustment_in_wc * dsn_air_flow_cfm / 4131
     OpenStudio.logFree(OpenStudio::Debug, 'openstudio.standards.AirLoopHVAC', "For #{air_loop_hvac.name}: Fan Power Limitation Pressure Drop Adjustment = #{fan_pwr_adjustment_bhp.round(2)} bhp")
 
@@ -461,11 +477,11 @@
           fan_pwr_limit_type = 'constant volume'
         elsif fan.to_FanVariableVolume.is_initialized
           fan_pwr_limit_type = 'variable volume'
         end
       elsif comp.to_AirLoopHVACUnitarySystem.is_initialized
-        fan = comp.to_AirLoopHVACUnitarySystem.get.supplyFan
+        fan = comp.to_AirLoopHVACUnitarySystem.get.supplyFan.get
         if fan.to_FanConstantVolume.is_initialized || comp.to_FanOnOff.is_initialized
           fan_pwr_limit_type = 'constant volume'
         elsif fan.to_FanVariableVolume.is_initialized
           fan_pwr_limit_type = 'variable volume'
         end
@@ -480,13 +496,21 @@
     end
 
     # Calculate the Allowable Fan System brake horsepower per Table G3.1.2.9
     allowable_fan_bhp = 0
     if fan_pwr_limit_type == 'constant volume'
-      allowable_fan_bhp = dsn_air_flow_cfm * 0.00094 + fan_pwr_adjustment_bhp
+      if dsn_air_flow_cfm > 0 
+        allowable_fan_bhp = dsn_air_flow_cfm * 0.00094 + fan_pwr_adjustment_bhp
+      else
+        allowable_fan_bhp = 0.00094
+      end
     elsif fan_pwr_limit_type == 'variable volume'
-      allowable_fan_bhp = dsn_air_flow_cfm * 0.0013 + fan_pwr_adjustment_bhp
+      if dsn_air_flow_cfm > 0 
+        allowable_fan_bhp = dsn_air_flow_cfm * 0.0013 + fan_pwr_adjustment_bhp
+      else
+        allowable_fan_bhp = 0.0013
+      end
     end
     OpenStudio.logFree(OpenStudio::Info, 'openstudio.standards.AirLoopHVAC', "For #{air_loop_hvac.name}: Allowable brake horsepower = #{allowable_fan_bhp.round(2)}HP based on #{dsn_air_flow_cfm.round} cfm and #{fan_pwr_adjustment_bhp.round(2)} bhp of adjustment.")
 
     # Calculate and report the total area for debugging/testing
     floor_area_served_m2 = air_loop_hvac_floor_area_served(air_loop_hvac)
@@ -496,11 +520,17 @@
       return allowable_fan_bhp
     end
 
     floor_area_served_ft2 = OpenStudio.convert(floor_area_served_m2, 'm^2', 'ft^2').get
     cfm_per_ft2 = dsn_air_flow_cfm / floor_area_served_ft2
-    cfm_per_hp = dsn_air_flow_cfm / allowable_fan_bhp
+
+    if allowable_fan_bhp.zero?
+      cfm_per_hp = 0  
+      OpenStudio.logFree(OpenStudio::Warn, 'openstudio.standards.AirLoopHVAC', "AirLoopHVAC #{air_loop_hvac.name} has zero allowable fan bhp, probably due to zero design air flow cfm'.")
+    else  
+      cfm_per_hp = dsn_air_flow_cfm / allowable_fan_bhp
+    end
     OpenStudio.logFree(OpenStudio::Debug, 'openstudio.standards.AirLoopHVAC', "For #{air_loop_hvac.name}: area served = #{floor_area_served_ft2.round} ft^2.")
     OpenStudio.logFree(OpenStudio::Debug, 'openstudio.standards.AirLoopHVAC', "For #{air_loop_hvac.name}: flow per area = #{cfm_per_ft2.round} cfm/ft^2.")
     OpenStudio.logFree(OpenStudio::Debug, 'openstudio.standards.AirLoopHVAC', "For #{air_loop_hvac.name}: flow per hp = #{cfm_per_hp.round} cfm/hp.")
 
     return allowable_fan_bhp
@@ -846,10 +876,10 @@
       'climate_zone' => climate_zone,
       'data_center' => is_dc
     }
     econ_limits = model_find_object(standards_data['economizers'], search_criteria)
     if econ_limits.nil?
-      OpenStudio.logFree(OpenStudio::Warn, 'openstudio.standards.AirLoopHVAC', "Cannot find economizer limits for #{template}, #{climate_zone}, assuming no economizer required.")
+      OpenStudio.logFree(OpenStudio::Warn, 'openstudio.standards.AirLoopHVAC', "Cannot find economizer limits for template '#{template}' and climate zone '#{climate_zone}', assuming no economizer required.")
       return economizer_required
     end
 
     # Determine the minimum capacity and whether or not it is a data center
     minimum_capacity_btu_per_hr = econ_limits['capacity_limit']