How are the DHW templates building out the water portion of the IDF file, like the following snippet? Is that done via Honeybee or OpenStudio? I have been having trouble tracking this down in the github repos.
IDF snippet
WaterUse:Connections,
Water Use Connections 4, !- Name
Node 90, !- Inlet Node Name
Node 91, !- Outlet Node Name
, !- Supply Water Storage Tank Name
, !- Reclamation Water Storage Tank Name
60.0C Hot Water, !- Hot Water Supply Temperature Schedule Name
, !- Cold Water Supply Temperature Schedule Name
None, !- Drain Water Heat Exchanger Type
Plant, !- Drain Water Heat Exchanger Destination
, !- Drain Water Heat Exchanger U-Factor Times Area {W/K}
2019::MidriseApartment::Apartment_SHW..PrimaryBathroom; !- Water Use Equipment Name 1
WaterUse:Equipment,
2019::MidriseApartment::Apartment_SHW..PrimaryBathroom, !- Name
General, !- End-Use Subcategory
8.90733228441169e-07, !- Peak Flow Rate {m3/s}
ApartmentMidRise APT_DHW_SCH, !- Flow Rate Fraction Schedule Name
60.0C Hot Water, !- Target Temperature Schedule Name
, !- Hot Water Supply Temperature Schedule Name
, !- Cold Water Supply Temperature Schedule Name
PrimaryBathroom, !- Zone Name
0.2 Hot Water Sensible Fraction, !- Sensible Fraction Schedule Name
0.05 Hot Water Latent Fraction; !- Latent Fraction Schedule Name
WaterHeater:Mixed,
SHW WaterHeater1, !- Name
0.114717965820617, !- Tank Volume {m3}
Schedule Ruleset 2, !- Setpoint Temperature Schedule Name
2, !- Deadband Temperature Difference {deltaC}
82.22, !- Maximum Temperature Limit {C}
Cycle, !- Heater Control Type
1000000, !- Heater Maximum Capacity {W}
, !- Heater Minimum Capacity {W}
0, !- Heater Ignition Minimum Flow Rate {m3/s}
0, !- Heater Ignition Delay {s}
Electricity, !- Heater Fuel Type
1, !- Heater Thermal Efficiency
, !- Part Load Factor Curve Name
20, !- Off Cycle Parasitic Fuel Consumption Rate {W}
Electricity, !- Off Cycle Parasitic Fuel Type
0.8, !- Off Cycle Parasitic Heat Fraction to Tank
0, !- On Cycle Parasitic Fuel Consumption Rate {W}
Electricity, !- On Cycle Parasitic Fuel Type
0, !- On Cycle Parasitic Heat Fraction to Tank
Schedule, !- Ambient Temperature Indicator
22.0C Ambient Condition, !- Ambient Temperature Schedule Name
, !- Ambient Temperature Zone Name
, !- Ambient Temperature Outdoor Air Node Name
0, !- Off Cycle Loss Coefficient to Ambient Temperature {W/K}
1, !- Off Cycle Loss Fraction to Zone
0, !- On Cycle Loss Coefficient to Ambient Temperature {W/K}
1, !- On Cycle Loss Fraction to Zone
, !- Peak Use Flow Rate {m3/s}
, !- Use Flow Rate Fraction Schedule Name
, !- Cold Water Supply Temperature Schedule Name
Node 79, !- Use Side Inlet Node Name
Node 84, !- Use Side Outlet Node Name
1, !- Use Side Effectiveness
, !- Source Side Inlet Node Name
, !- Source Side Outlet Node Name
1, !- Source Side Effectiveness
Autosize, !- Use Side Design Flow Rate {m3/s}
Autosize, !- Source Side Design Flow Rate {m3/s}
1.5, !- Indirect Water Heating Recovery Time {hr}
IndirectHeatPrimarySetpoint, !- Source Side Flow Control Mode
, !- Indirect Alternate Setpoint Temperature Schedule Name
General; !- End-Use Subcategory
The reason I am asking is that the current templates (at least for “Electric_WaterHeater”) lead to a large number of spurious warnings like the following:
Warnings
** Warning ** CalcEquipmentFlowRates: "2019::MIDRISEAPARTMENT::APARTMENT_SHW..PRIMARYBATHROOM" - Target water temperature is greater than the hot water temperature by (1.04 C)
** ~~~ ** Environment=RUN PERIOD 1, at Simulation time=01/01 00:00 - 00:10
** ~~~ ** ...target water temperature = 60.00 C
** ~~~ ** ...hot water temperature = 58.96 C
** ~~~ ** ...Target water temperature should be less than or equal to the hot water temperature. Verify temperature setpoints and schedules.
The reason for the warnings is that the same hourly temperature schedule is used for the WaterHeater:Mixed setpoint temperature and for the WaterUse:Equipment target temperature schedule. However, the water heater has a deadband and can deliver water at lower temperatures than in this schedule (by up to 2C for the IDF snippet above), meaning the water use equipment cannot deliver water at the requested temperature, leading to warnings at essentially every timestep in the EnergyPlus simulation. The solution would be to either increase the water heater setpoint or decrease the equipment target temperature by the deadband amount.
In practice, this has little impact on the DHW energy consumption, but I would love to be able to remove all these warnings from the EnergyPlus error file so it is easier to find the more useful warnings and errors in there. On an otherwise well-behaved 25 zone model I am currently working on, these errors account for approximately 300 lines (50%) of the error log.
