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Replace mains water temperature schedule w/ E+ built-in correlation #1983

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130 changes: 72 additions & 58 deletions HPXMLtoOpenStudio/resources/hotwater_appliances.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -382,27 +382,23 @@ def self.apply(runner, model, weather, spaces, hpxml_bldg, hpxml_header, schedul
frac_low_flow_fixtures = 0.0
end

# Calculate mixed water fractions
t_mix = 105.0 # F, Temperature of mixed water at fixtures
avg_setpoint_temp = 0.0 # WH Setpoint: Weighted average by fraction DHW load served
hpxml_bldg.water_heating_systems.each do |water_heating_system|
wh_setpoint = water_heating_system.temperature
wh_setpoint = Defaults.get_water_heater_temperature(eri_version) if wh_setpoint.nil? # using detailed schedules
avg_setpoint_temp += wh_setpoint * water_heating_system.fraction_dhw_load_served

# Set mains water temperature
swmt = model.getSiteWaterMainsTemperature
swmt.setCalculationMethod('Correlation')
swmt.setAnnualAverageOutdoorAirTemperature(UnitConversions.convert(weather.data.AnnualAvgDrybulb, 'F', 'C'))
swmt.setMaximumDifferenceInMonthlyAverageOutdoorAirTemperatures(UnitConversions.convert(weather.data.MonthlyAvgDrybulbs.max - weather.data.MonthlyAvgDrybulbs.min, 'deltaF', 'deltaC'))
if (not hot_water_distribution.dwhr_efficiency.nil?)
# FIXME: Requires new OS/E+ feature
# Calculate DWHR temperature multiplier/offset
# dwhr_factor, dhwr_in_t = get_dwhr_values(nbeds, n_occ, unit_type, hot_water_distribution, frac_low_flow_fixtures)
# temp_mult = 1.0 - dwhr_factor
# temp_offset = dwhr_factor * dhwr_in_t
# temp_offset_c = 5.0/9.0 * (32.0 * temp_mult + temp_offset - 32.0) # Convert adjustment to EnergyPlus input of deg-C
# swmt.setTemperatureMultiplier(temp_mult)
# swmt.setTemperatureOffset(temp_offset_c)
end
daily_wh_inlet_temperatures = calc_water_heater_daily_inlet_temperatures(weather, nbeds, n_occ, unit_type, hot_water_distribution, frac_low_flow_fixtures)
daily_wh_inlet_temperatures_c = daily_wh_inlet_temperatures.map { |t| UnitConversions.convert(t, 'F', 'C') }
daily_mw_fractions = calc_mixed_water_daily_fractions(daily_wh_inlet_temperatures, avg_setpoint_temp, t_mix)

# Schedules
# Replace mains water temperature schedule with water heater inlet temperature schedule.
# These are identical unless there is a DWHR.
start_date = OpenStudio::Date.new(OpenStudio::MonthOfYear.new(1), 1, hpxml_header.sim_calendar_year)
timestep_day = OpenStudio::Time.new(1, 0)
time_series_tmains = OpenStudio::TimeSeries.new(start_date, timestep_day, OpenStudio::createVector(daily_wh_inlet_temperatures_c), 'C')
schedule_tmains = OpenStudio::Model::ScheduleInterval.fromTimeSeries(time_series_tmains, model).get
schedule_tmains.setName('mains temperature schedule')
model.getSiteWaterMainsTemperature.setTemperatureSchedule(schedule_tmains)

mw_temp_schedule = Model.add_schedule_constant(
model,
Expand Down Expand Up @@ -432,13 +428,18 @@ def self.apply(runner, model, weather, spaces, hpxml_bldg, hpxml_header, schedul
end
end

if Constants::ERIVersions.index(eri_version) < Constants::ERIVersions.index('2014A')
# Calculate annual average mixed water fraction
avg_mw_fraction = calc_mixed_water_fraction(hpxml_bldg, t_mix, weather, nbeds, n_occ, unit_type, hot_water_distribution, frac_low_flow_fixtures, eri_version)
end

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)

gpd_frac = water_heating_system.fraction_dhw_load_served # Fixtures fraction
if gpd_frac > 0

fx_gpd = get_fixtures_gpd(eri_version, nbeds, frac_low_flow_fixtures, daily_mw_fractions, fixtures_usage_multiplier, n_occ)
fx_gpd = get_fixtures_gpd(eri_version, nbeds, frac_low_flow_fixtures, avg_mw_fraction, fixtures_usage_multiplier, n_occ)
w_gpd = get_dist_waste_gpd(eri_version, nbeds, has_uncond_bsmnt, has_cond_bsmnt, cfa, ncfl, hot_water_distribution, frac_low_flow_fixtures, fixtures_usage_multiplier, n_occ)

fx_peak_flow = nil
Expand Down Expand Up @@ -1037,15 +1038,24 @@ def self.get_fridge_or_freezer_coefficients_schedule(model, col_name, obj_name,
return schedule
end

# Calculates Drain Water Heat Recovery (DWHR) factors.
# Returns Drain Water Heat Recovery (DWHR) aggregate factor and temperature.
#
# Source: ANSI/RESNET/ICC 301
#
# @param nbeds_eq [Integer] Number of bedrooms (or equivalent bedrooms, as adjusted by the number of occupants) in the dwelling unit
# @param nbeds [Integer] Number of bedrooms in the dwelling unit
# @param n_occ [Double] Number of occupants in the dwelling unit
# @param unit_type [String] Type of dwelling unit (HXPML::ResidentialTypeXXX)
# @param hot_water_distribution [HPXML::HotWaterDistribution] The HPXML hot water distribution system of interest
# @param frac_low_flow_fixtures [Double] The fraction of fixtures considered low-flow
# @return [Array<Double, Double, Double, Double, Double>] Effectiveness (frac), fraction of water impacted by DWHR, piping loss coefficient, location factor, fixture factor
def self.get_dwhr_factors(nbeds_eq, hot_water_distribution, frac_low_flow_fixtures)
# @return [Array<Double, Double>] Aggregate factor (frac), temperature (F)
def self.get_dwhr_values(nbeds, n_occ, unit_type, hot_water_distribution, frac_low_flow_fixtures)
if n_occ == 0
# Operational calculation w/ zero occupants
nbeds_eq = 0
else
nbeds_eq = Defaults.get_equivalent_nbeds(nbeds, n_occ, unit_type)
end

# ANSI/RESNET/ICC 301-2022 Eq. 4.2-42

eff_adj = 1.0 + 0.082 * frac_low_flow_fixtures
Expand Down Expand Up @@ -1073,34 +1083,50 @@ def self.get_dwhr_factors(nbeds_eq, hot_water_distribution, frac_low_flow_fixtur
fix_f = 0.5
end

return eff_adj, i_frac, plc, loc_f, fix_f
dwhr_factor = eff_adj * i_frac * plc * loc_f * fix_f * hot_water_distribution.dwhr_efficiency # Aggregate factor
dhwr_in_t = 97.0 # deg-F

return dwhr_factor, dhwr_in_t
end

# Calculates daily water heater inlet temperatures, which includes an adjustment if
# there is a drain water heat recovery device.
#
# Source: ANSI/RESNET/ICC 301
#
# @return [Array<Double>] Daily water heater inlet temperatures (F)
def self.calc_water_heater_daily_inlet_temperatures()
end

# Calculates the annual average mixed water adjustment fraction. The fraction converts from
# gallons of mixed water to gallons of hot water that needs to be served by the water heater.
#
# @param hpxml_bldg [HPXML::Building] HPXML Building object representing an individual dwelling unit
# @param t_mix [Double] Temperature of mixed water at fixtures (F)
# @param weather [WeatherFile] Weather object containing EPW information
# @param nbeds [Integer] Number of bedrooms in the dwelling unit
# @param n_occ [Double] Number of occupants in the dwelling unit
# @param unit_type [String] Type of dwelling unit (HXPML::ResidentialTypeXXX)
# @param hot_water_distribution [HPXML::HotWaterDistribution] The HPXML hot water distribution system of interest
# @param frac_low_flow_fixtures [Double] The fraction of fixtures considered low-flow
# @return [Array<Double>] Daily water heater inlet temperatures (F)
def self.calc_water_heater_daily_inlet_temperatures(weather, nbeds, n_occ, unit_type, hot_water_distribution, frac_low_flow_fixtures)
if n_occ == 0
# Operational calculation w/ zero occupants
nbeds_eq = 0
else
nbeds_eq = Defaults.get_equivalent_nbeds(nbeds, n_occ, unit_type)
# @param eri_version [String] Version of the ANSI/RESNET/ICC 301 Standard to use for equations/assumptions
# @return [Double] Annual average mixed water adjustment fraction
def self.calc_mixed_water_fraction(hpxml_bldg, t_mix, weather, nbeds, n_occ, unit_type, hot_water_distribution, frac_low_flow_fixtures, eri_version)
# WH Setpoint: Weighted average by fraction DHW load served
t_set = 0.0
hpxml_bldg.water_heating_systems.each do |water_heating_system|
wh_setpoint = water_heating_system.temperature
wh_setpoint = Defaults.get_water_heater_temperature(eri_version) if wh_setpoint.nil? # using detailed schedules
t_set += wh_setpoint * water_heating_system.fraction_dhw_load_served
end

# Calculates daily water heater inlet temperatures, which includes an adjustment if
# there is a drain water heat recovery device.
wh_temps_daily = weather.data.MainsDailyTemps.dup
if (not hot_water_distribution.dwhr_efficiency.nil?)
# Per ANSI/RESNET/ICC 301
dwhr_eff_adj, dwhr_iFrac, dwhr_plc, dwhr_locF, dwhr_fixF = get_dwhr_factors(nbeds_eq, hot_water_distribution, frac_low_flow_fixtures)
dwhr_factor, dhwr_in_t = get_dwhr_values(nbeds, n_occ, unit_type, hot_water_distribution, frac_low_flow_fixtures)

# Adjust inlet temperatures
dwhr_inT = 97.0 # F
for day in 0..wh_temps_daily.size - 1
dwhr_WHinTadj = dwhr_iFrac * (dwhr_inT - wh_temps_daily[day]) * hot_water_distribution.dwhr_efficiency * dwhr_eff_adj * dwhr_plc * dwhr_locF * dwhr_fixF
dwhr_WHinTadj = (dhwr_in_t - wh_temps_daily[day]) * dwhr_factor
wh_temps_daily[day] = (wh_temps_daily[day] + dwhr_WHinTadj).round(3)
end
else
Expand All @@ -1109,24 +1135,13 @@ def self.calc_water_heater_daily_inlet_temperatures(weather, nbeds, n_occ, unit_
end
end

return wh_temps_daily
end

# Calculates the daily mixed water adjustment fractions. These fractions convert from
# gallons of mixed water to gallons of hot water that needs to be served by the water heater.
#
# @param daily_wh_inlet_temperatures [Array<Double>] Daily water heater inlet temperatures (F)
# @param t_set [Double] Water heater setpoint temperature (F)
# @param t_use [Double] Temperature of mixed water at fixtures (F)
# @return [Array<Double>] Daily mixed water adjustment fractions
def self.calc_mixed_water_daily_fractions(daily_wh_inlet_temperatures, t_set, t_use)
# Per ANSI/RESNET/ICC 301
# Calculate daily adjustment fractions
adj_f_mix = []
for day in 0..daily_wh_inlet_temperatures.size - 1
adj_f_mix << (1.0 - ((t_set - t_use) / (t_set - daily_wh_inlet_temperatures[day]))).round(4)
for day in 0..wh_temps_daily.size - 1
adj_f_mix << (1.0 - ((t_set - t_mix) / (t_set - wh_temps_daily[day]))).round(4)
end

return adj_f_mix
return adj_f_mix.sum / Float(adj_f_mix.size)
end

# Calculates annual energy use for a recirculation (or shared recirculation) hot water
Expand Down Expand Up @@ -1195,11 +1210,11 @@ def self.get_fixtures_effectiveness(frac_low_flow_fixtures)
# @param eri_version [String] Version of the ANSI/RESNET/ICC 301 Standard to use for equations/assumptions
# @param nbeds [Integer] Number of bedrooms in the dwelling unit
# @param frac_low_flow_fixtures [Double] The fraction of fixtures considered low-flow
# @param daily_mw_fractions [Array<Double>] Daily mixed water adjustment fractions
# @param avg_mw_fraction [Double] Annual average mixed water fraction
# @param fixtures_usage_multiplier [Double] Occupant usage multiplier
# @param n_occ [Double] Number of occupants in the dwelling unit
# @return [Double] Mixed water use (gal/day)
def self.get_fixtures_gpd(eri_version, nbeds, frac_low_flow_fixtures, daily_mw_fractions, fixtures_usage_multiplier = 1.0, n_occ = nil)
def self.get_fixtures_gpd(eri_version, nbeds, frac_low_flow_fixtures, avg_mw_fraction, fixtures_usage_multiplier = 1.0, n_occ = nil)
if Constants::ERIVersions.index(eri_version) >= Constants::ERIVersions.index('2014A')
if n_occ.nil? # Asset calculation
ref_f_gpd = 14.6 + 10.0 * nbeds # ANSI/RESNET/ICC 301-2022 Eq. 4.2-29 (refFgpd)
Expand All @@ -1210,9 +1225,8 @@ def self.get_fixtures_gpd(eri_version, nbeds, frac_low_flow_fixtures, daily_mw_f
return f_eff * ref_f_gpd * fixtures_usage_multiplier
else
hw_gpd = 30.0 + 10.0 * nbeds # Table 4.2.2(1) Service water heating systems
# Convert to mixed water gpd
avg_mw_fraction = daily_mw_fractions.reduce(:+) / daily_mw_fractions.size.to_f
return hw_gpd / avg_mw_fraction * fixtures_usage_multiplier
mw_gpd = hw_gpd / avg_mw_fraction # Convert to mixed water gpd
return mw_gpd * fixtures_usage_multiplier
end
end

Expand Down
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