120V HPWHs, take 2

Changelog.md

@@ -5,6 +5,9 @@ __New Features__
   - Dual-fuel heat pumps with switchover temperatures > 25F are now autosized based on 25F to allow some additional heating capacity buffer.
   - Improves handling of duct leakage specified using cfm25/cfm50.
   - Crankcase heating energy is now disabled during unavailable periods, e.g., power outages.
+- Water heater updates:
+  - Allows modeling 120V HPWHs (including dedicated vs shared circuits) using `WaterHeatingSystem/HPWHVoltage`.
+  - Allows modeling water heaters with a mixing valve using `HasMixingValve` and `MixingValveSetpoint`.
 - Allows "other" for `SoilType`; adds variation to dry/wet soil conductivity and diffusivity values for unknown/other/loam soil types.
 - Output updates:
   - **Breaking change**: Annual peak load outputs for heating and cooling now use units of Btu/h instead of kBtu/h for consistency with other outputs.

HPXMLtoOpenStudio/measure.xml

@@ -3,8 +3,8 @@
   <schema_version>3.1</schema_version>
   <name>hpxml_to_openstudio</name>
   <uid>b1543b30-9465-45ff-ba04-1d1f85e763bc</uid>
-  <version_id>8b05dfcf-bf6e-4880-8280-e89fa9ac1f1d</version_id>
-  <version_modified>2026-04-24T15:17:55Z</version_modified>
+  <version_id>e3879ee8-dd46-4587-bf50-45f7b0eb092f</version_id>
+  <version_modified>2026-04-27T16:06:36Z</version_modified>
   <xml_checksum>D8922A73</xml_checksum>
   <class_name>HPXMLToOpenStudio</class_name>
   <display_name>HPXML to OpenStudio Translator</display_name>
@@ -367,7 +367,7 @@
       <filename>defaults.rb</filename>
       <filetype>rb</filetype>
       <usage_type>resource</usage_type>
-      <checksum>F91B9101</checksum>
+      <checksum>93CB275C</checksum>
     </file>
     <file>
       <filename>electric_panel.rb</filename>
@@ -397,13 +397,13 @@
       <filename>hotwater_appliances.rb</filename>
       <filetype>rb</filetype>
       <usage_type>resource</usage_type>
-      <checksum>5F185DC6</checksum>
+      <checksum>82516F0C</checksum>
     </file>
     <file>
       <filename>hpxml.rb</filename>
       <filetype>rb</filetype>
       <usage_type>resource</usage_type>
-      <checksum>BF5902DA</checksum>
+      <checksum>3C44E95B</checksum>
     </file>
     <file>
       <filename>hpxml_schema/HPXML.xsd</filename>
@@ -421,7 +421,7 @@
       <filename>hpxml_schematron/EPvalidator.sch</filename>
       <filetype>sch</filetype>
       <usage_type>resource</usage_type>
-      <checksum>9B5934A8</checksum>
+      <checksum>B163569D</checksum>
     </file>
     <file>
       <filename>hpxml_schematron/iso-schematron.xsd</filename>
@@ -715,7 +715,7 @@
       <filename>waterheater.rb</filename>
       <filetype>rb</filetype>
       <usage_type>resource</usage_type>
-      <checksum>245FEA65</checksum>
+      <checksum>08232D17</checksum>
     </file>
     <file>
       <filename>weather.rb</filename>
@@ -751,13 +751,13 @@
       <filename>test_defaults.rb</filename>
       <filetype>rb</filetype>
       <usage_type>test</usage_type>
-      <checksum>191743A2</checksum>
+      <checksum>C8BD974C</checksum>
     </file>
     <file>
       <filename>test_electric_panel.rb</filename>
       <filetype>rb</filetype>
       <usage_type>test</usage_type>
-      <checksum>8E69A0EB</checksum>
+      <checksum>374CB236</checksum>
     </file>
     <file>
       <filename>test_enclosure.rb</filename>
@@ -775,7 +775,7 @@
       <filename>test_hotwater_appliance.rb</filename>
       <filetype>rb</filetype>
       <usage_type>test</usage_type>
-      <checksum>6DBBC0A9</checksum>
+      <checksum>0A4D986F</checksum>
     </file>
     <file>
       <filename>test_hvac.rb</filename>
@@ -829,7 +829,7 @@
       <filename>test_validation.rb</filename>
       <filetype>rb</filetype>
       <usage_type>test</usage_type>
-      <checksum>FD24774E</checksum>
+      <checksum>3A631903</checksum>
     </file>
     <file>
       <filename>test_vehicle.rb</filename>
@@ -841,7 +841,7 @@
       <filename>test_water_heater.rb</filename>
       <filetype>rb</filetype>
       <usage_type>test</usage_type>
-      <checksum>8DBA3BD3</checksum>
+      <checksum>61A61CD2</checksum>
     </file>
     <file>
       <filename>test_weather.rb</filename>

HPXMLtoOpenStudio/resources/defaults.rb

@@ -3358,15 +3358,31 @@ def self.apply_water_heaters(hpxml_bldg, eri_version, schedules_file)
         end
 
       elsif water_heating_system.water_heater_type == HPXML::WaterHeaterTypeHeatPump
+
+        if water_heating_system.hpwh_voltage.nil?
+          water_heating_system.hpwh_voltage = HPXML::HPWHVoltage240
+          water_heating_system.hpwh_voltage_isdefaulted = true
+        end
+
         water_heating_system.additional_properties.cop = get_water_heater_heat_pump_cop(water_heating_system)
 
         if water_heating_system.heating_capacity.nil?
-          water_heating_system.heating_capacity = (UnitConversions.convert(0.5, 'kW', 'Btu/hr') * water_heating_system.additional_properties.cop).round
+          if water_heating_system.hpwh_voltage == HPXML::HPWHVoltage240
+            water_heating_system.heating_capacity = (UnitConversions.convert(0.5, 'kW', 'Btu/hr') * water_heating_system.additional_properties.cop).round
+          elsif water_heating_system.hpwh_voltage == HPXML::HPWHVoltage120Dedicated
+            water_heating_system.heating_capacity = (UnitConversions.convert(0.422, 'kW', 'Btu/hr') * water_heating_system.additional_properties.cop).round
+          else # 120V shared
+            water_heating_system.heating_capacity = (UnitConversions.convert(0.357, 'kW', 'Btu/hr') * water_heating_system.additional_properties.cop).round
+          end
           water_heating_system.heating_capacity_isdefaulted = true
         end
 
         if water_heating_system.backup_heating_capacity.nil?
-          water_heating_system.backup_heating_capacity = UnitConversions.convert(4.5, 'kW', 'Btu/hr').round
+          if water_heating_system.hpwh_voltage == HPXML::HPWHVoltage240
+            water_heating_system.backup_heating_capacity = UnitConversions.convert(4.5, 'kW', 'Btu/hr').round
+          else
+            water_heating_system.backup_heating_capacity = 0.0 # No backup elements
+          end
           water_heating_system.backup_heating_capacity_isdefaulted = true
         end
 
@@ -3387,6 +3403,22 @@ def self.apply_water_heaters(hpxml_bldg, eri_version, schedules_file)
         end
 
       end
+
+      if water_heating_system.has_mixing_valve.nil?
+        if water_heating_system.water_heater_type == HPXML::WaterHeaterTypeHeatPump && water_heating_system.hpwh_voltage != HPXML::HPWHVoltage240
+          # 120V HPWH
+          water_heating_system.has_mixing_valve = true
+        else
+          water_heating_system.has_mixing_valve = false
+        end
+        water_heating_system.has_mixing_valve_isdefaulted = true
+      end
+
+      if water_heating_system.has_mixing_valve && water_heating_system.mixing_valve_setpoint.nil?
+        water_heating_system.mixing_valve_setpoint = [125.0, water_heating_system.temperature].min
+        water_heating_system.mixing_valve_setpoint_isdefaulted = true
+      end
+
       next unless water_heating_system.location.nil?
 
       iecc_zone = hpxml_bldg.climate_and_risk_zones.climate_zone_ieccs.empty? ? nil : hpxml_bldg.climate_and_risk_zones.climate_zone_ieccs[0].zone
@@ -6120,6 +6152,7 @@ def self.get_water_heater_location(hpxml_bldg, iecc_zone = nil)
   # @param eri_version [String] Version of the ANSI/RESNET/ICC 301 Standard to use for equations/assumptions
   # @return [Double] Water heater setpoint temperature (F)
   def self.get_water_heater_temperature(eri_version)
+    # FIXME: Should we default to a different value for 120V HPWHs?
     if Constants::ERIVersions.index(eri_version) >= Constants::ERIVersions.index('2014A')
       # 2014 w/ Addendum A or newer
       return 125.0
@@ -6268,22 +6301,28 @@ def self.get_water_heater_tank_volume(fuel, is_hpwh, nbeds, nbaths, n_occ)
   # @param water_heating_system [HPXML::WaterHeatingSystem] The HPXML water heating system of interest
   # @return [Double] COP of the heat pump (W/W)
   def self.get_water_heater_heat_pump_cop(water_heating_system)
-    # Based on simulations of the UEF test procedure at varying COPs
-    if not water_heating_system.energy_factor.nil?
-      uef = (0.60522 + water_heating_system.energy_factor) / 1.2101
-      cop = 1.174536058 * uef
-    elsif not water_heating_system.uniform_energy_factor.nil?
-      uef = water_heating_system.uniform_energy_factor
-      case water_heating_system.usage_bin
-      when HPXML::WaterHeaterUsageBinVerySmall
-        fail 'It is unlikely that a heat pump water heater falls into the very small bin of the First Hour Rating (FHR) test. Double check input.'
-      when HPXML::WaterHeaterUsageBinLow
-        cop = 1.0005 * uef - 0.0789
-      when HPXML::WaterHeaterUsageBinMedium
-        cop = 1.0909 * uef - 0.0868
-      when HPXML::WaterHeaterUsageBinHigh
-        cop = 1.1022 * uef - 0.0877
-      end
+    if water_heating_system.hpwh_voltage == HPXML::HPWHVoltage240
+      # Based on simulations of the UEF test procedure at varying COPs
+      if not water_heating_system.energy_factor.nil?
+        uef = (0.60522 + water_heating_system.energy_factor) / 1.2101
+        cop = 1.174536058 * uef
+      elsif not water_heating_system.uniform_energy_factor.nil?
+        uef = water_heating_system.uniform_energy_factor
+        case water_heating_system.usage_bin
+        when HPXML::WaterHeaterUsageBinVerySmall
+          fail 'It is unlikely that a heat pump water heater falls into the very small bin of the First Hour Rating (FHR) test. Double check input.'
+        when HPXML::WaterHeaterUsageBinLow
+          cop = 1.0005 * uef - 0.0789
+        when HPXML::WaterHeaterUsageBinMedium
+          cop = 1.0909 * uef - 0.0868
+        when HPXML::WaterHeaterUsageBinHigh
+          cop = 1.1022 * uef - 0.0877
+        end
+      end
+    elsif water_heating_system.hpwh_voltage == HPXML::HPWHVoltage120Dedicated
+      cop = 3.6
+    else # 120V shared
+      cop = 4.2
     end
     return cop
   end
@@ -6826,8 +6865,17 @@ def self.get_branch_circuit_voltage_default_values(branch_circuit)
         end
       elsif component.is_a?(HPXML::PVSystem)
         voltages << HPXML::ElectricPanelVoltage240
-      elsif component.is_a?(HPXML::WaterHeatingSystem) ||
-            component.is_a?(HPXML::ClothesDryer) ||
+      elsif component.is_a?(HPXML::WaterHeatingSystem)
+        if component.fuel_type == HPXML::FuelTypeElectricity
+          if component.hpwh_voltage.nil? # Not HPWH
+            voltages << HPXML::ElectricPanelVoltage240
+          elsif component.hpwh_voltage == HPXML::HPWHVoltage240
+            voltages << HPXML::ElectricPanelVoltage240
+          else # 120V HPWH
+            voltages << HPXML::ElectricPanelVoltage120
+          end
+        end
+      elsif component.is_a?(HPXML::ClothesDryer) ||
             component.is_a?(HPXML::CookingRange)
         if component.fuel_type == HPXML::FuelTypeElectricity
           voltages << HPXML::ElectricPanelVoltage240

HPXMLtoOpenStudio/resources/hotwater_appliances.rb

@@ -380,6 +380,16 @@ def self.apply(runner, model, weather, spaces, hpxml_bldg, hpxml_header, schedul
     hpxml_bldg.water_heating_systems.each do |water_heating_system|
       non_solar_fraction = 1.0 - Waterheater.get_water_heater_solar_fraction(water_heating_system, hpxml_bldg)
 
+      hw_temp_schedule = nil
+      if water_heating_system.has_mixing_valve
+        hw_temp_schedule = Model.add_schedule_constant(
+          model,
+          name: 'hot water temperature schedule',
+          value: UnitConversions.convert(water_heating_system.mixing_valve_setpoint, 'F', 'C'),
+          limits: EPlus::ScheduleTypeLimitsTemperature
+        )
+      end
+
       gpd_frac = water_heating_system.fraction_dhw_load_served # Fixtures fraction
       if gpd_frac > 0
 
@@ -489,7 +499,7 @@ def self.apply(runner, model, weather, spaces, hpxml_bldg, hpxml_header, schedul
             peak_flow_rate: unit_multiplier * cw_peak_flow * gpd_frac * non_solar_fraction,
             flow_rate_schedule: water_cw_schedule,
             water_use_connections: water_use_connections[water_heating_system.id],
-            target_temperature_schedule: nil
+            target_temperature_schedule: hw_temp_schedule
           )
           cw_wue.additionalProperties.setFeature('HPXML_ID', water_heating_system.id) # Used by reporting measure
         end
@@ -526,7 +536,7 @@ def self.apply(runner, model, weather, spaces, hpxml_bldg, hpxml_header, schedul
         peak_flow_rate: unit_multiplier * dw_peak_flow * gpd_frac * non_solar_fraction,
         flow_rate_schedule: water_dw_schedule,
         water_use_connections: water_use_connections[water_heating_system.id],
-        target_temperature_schedule: nil
+        target_temperature_schedule: hw_temp_schedule
       )
       dw_wue.additionalProperties.setFeature('HPXML_ID', water_heating_system.id) # Used by reporting measure
     end

HPXMLtoOpenStudio/resources/hpxml.rb

@@ -224,6 +224,10 @@ class HPXML < Object
   HeatPumpSizingACCA = 'ACCA'
   HeatPumpSizingHERS = 'HERS'
   HeatPumpSizingMaxLoad = 'MaxLoad'
+  HPWHVoltage240 = '240V'
+  HPWHVoltage120 = '120V'
+  HPWHVoltage120Dedicated = '120V dedicated circuit'
+  HPWHVoltage120Shared = '120V shared circuit'
   HVACCompressorTypeSingleStage = 'single stage'
   HVACCompressorTypeTwoStage = 'two stage'
   HVACCompressorTypeVariableSpeed = 'variable speed'
@@ -8595,6 +8599,7 @@ class WaterHeatingSystem < BaseElement
              :energy_factor,                          # [Double] EnergyFactor (frac)
              :uniform_energy_factor,                  # [Double] UniformEnergyFactor (frac)
              :hpwh_operating_mode,                    # [String] HPWHOperatingMode (HPXML::WaterHeaterHPWHOperatingModeXXX)
+             :hpwh_voltage,                           # [String] HPWHVoltage (HPXML::HPWHVoltageXXX)
              :hpwh_ducting_supply,                    # [String] HPWHDucting/SupplyAirSource (HPXML::LocationXXX)
              :hpwh_ducting_exhaust,                   # [String] HPWHDucting/ExhaustAirTermination (HPXML::LocationXXX)
              :first_hour_rating,                      # [Double] FirstHourRating (gal/hr)
@@ -8604,6 +8609,8 @@ class WaterHeatingSystem < BaseElement
              :standby_loss_units,                     # [String] StandbyLoss/Units (HPXML::UnitsXXX)
              :standby_loss_value,                     # [Double] StandbyLoss/Value
              :temperature,                            # [Double] HotWaterTemperature (F)
+             :has_mixing_valve,                       # [Boolean] HasMixingValve
+             :mixing_valve_setpoint,                  # [Double] MixingValveSetpoint (F)
              :uses_desuperheater,                     # [Boolean] UsesDesuperheater
              :related_hvac_idref,                     # [String] RelatedHVACSystem/@idref
              :tank_model_type,                        # [String] extension/TankModelType (HPXML::WaterHeaterTankModelTypeXXX)
@@ -8698,6 +8705,7 @@ def to_doc(building)
       XMLHelper.add_element(water_heating_system, 'EnergyFactor', @energy_factor, :float, @energy_factor_isdefaulted) unless @energy_factor.nil?
       XMLHelper.add_element(water_heating_system, 'UniformEnergyFactor', @uniform_energy_factor, :float) unless @uniform_energy_factor.nil?
       XMLHelper.add_element(water_heating_system, 'HPWHOperatingMode', @hpwh_operating_mode, :string, @hpwh_operating_mode_isdefaulted) unless @hpwh_operating_mode.nil?
+      XMLHelper.add_element(water_heating_system, 'HPWHVoltage', @hpwh_voltage, :string, @hpwh_voltage_isdefaulted) unless @hpwh_voltage.nil?
       if (not @hpwh_ducting_exhaust.nil?) || (not @hpwh_ducting_supply.nil?)
         hpwh_ducting = XMLHelper.add_element(water_heating_system, 'HPWHDucting')
         XMLHelper.add_element(hpwh_ducting, 'SupplyAirSource', @hpwh_ducting_supply, :string, @hpwh_ducting_supply_isdefaulted) unless @hpwh_ducting_supply.nil?
@@ -8717,6 +8725,8 @@ def to_doc(building)
         XMLHelper.add_element(standby_loss, 'Value', @standby_loss_value, :float, @standby_loss_value_isdefaulted)
       end
       XMLHelper.add_element(water_heating_system, 'HotWaterTemperature', @temperature, :float, @temperature_isdefaulted) unless @temperature.nil?
+      XMLHelper.add_element(water_heating_system, 'HasMixingValve', @has_mixing_valve, :boolean, @has_mixing_valve_isdefaulted) unless @has_mixing_valve.nil?
+      XMLHelper.add_element(water_heating_system, 'MixingValveSetpoint', @mixing_valve_setpoint, :float, @mixing_valve_setpoint_isdefaulted) unless @mixing_valve_setpoint.nil?
       XMLHelper.add_element(water_heating_system, 'UsesDesuperheater', @uses_desuperheater, :boolean) unless @uses_desuperheater.nil?
       if not @related_hvac_idref.nil?
         related_hvac_idref_el = XMLHelper.add_element(water_heating_system, 'RelatedHVACSystem')
@@ -8753,6 +8763,7 @@ def from_doc(water_heating_system)
       @energy_factor = XMLHelper.get_value(water_heating_system, 'EnergyFactor', :float)
       @uniform_energy_factor = XMLHelper.get_value(water_heating_system, 'UniformEnergyFactor', :float)
       @hpwh_operating_mode = XMLHelper.get_value(water_heating_system, 'HPWHOperatingMode', :string)
+      @hpwh_voltage = XMLHelper.get_value(water_heating_system, 'HPWHVoltage', :string)
       @hpwh_ducting_supply = XMLHelper.get_value(water_heating_system, 'HPWHDucting/SupplyAirSource', :string)
       @hpwh_ducting_exhaust = XMLHelper.get_value(water_heating_system, 'HPWHDucting/ExhaustAirTermination', :string)
       @first_hour_rating = XMLHelper.get_value(water_heating_system, 'FirstHourRating', :float)
@@ -8762,6 +8773,8 @@ def from_doc(water_heating_system)
       @standby_loss_units = XMLHelper.get_value(water_heating_system, 'StandbyLoss/Units', :string)
       @standby_loss_value = XMLHelper.get_value(water_heating_system, 'StandbyLoss/Value', :float)
       @temperature = XMLHelper.get_value(water_heating_system, 'HotWaterTemperature', :float)
+      @has_mixing_valve = XMLHelper.get_value(water_heating_system, 'HasMixingValve', :boolean)
+      @mixing_valve_setpoint = XMLHelper.get_value(water_heating_system, 'MixingValveSetpoint', :float)
       @uses_desuperheater = XMLHelper.get_value(water_heating_system, 'UsesDesuperheater', :boolean)
       @related_hvac_idref = HPXML::get_idref(XMLHelper.get_element(water_heating_system, 'RelatedHVACSystem'))
       @tank_model_type = XMLHelper.get_value(water_heating_system, 'extension/TankModelType', :string)