Service Hot Water can be accessed through two different library categories - Zonal Equipment and Water Equipment.
The Type and Sub Type options that can be selected from the drop down lists in that area of the workspace, which filter the Source Library to display the variables the user can select to include, along with a value, in a Library Entry.
Note: The links within the table are to the EnergyPlus Input Output Reference and the explanations of the objects.
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Plumbing Terminal |
Hot Water Fixture Set Plumbing Fixture Swimming Pool |
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The WaterHeater:Mixed object analytically solves the differential equation governing the energy balance of the water tank. Within a timestep, conditions are solved separately for when the heater element or burner is "on" (on-cycle) and when it is "off" (off-cycle). This approach allows ambient losses and parasitic loads to be divided into on-cycle and off-cycle effects and accounted for in detail.
For losses to the ambient environment, the ambient air temperature can be taken from a schedule, a zone, or the exterior. When used with a zone, a fraction of the skin losses can be added to the zone heat balance as internal heat gains.
Control options allow the heater to cycle or modulate to meet the load. When cycling, the heater element or burner is either on or off. The heater remains fully on while heating the tank up to the setpoint temperature. When the setpoint is reached, the heater turns off. The heater remains off until the tank temperature falls below the "cut-in" temperature, i.e., the setpoint temperature minus the deadband temperature difference. The heater continuously cycles on and off to maintain the tank temperature within the deadband. Most storage-tank water heaters cycle.
When modulating, the heater power varies between the maximum and minimum heater capacities. The heater stays on as long as the required total demand is above the minimum capacity. Below the minimum capacity, the heater will begin to cycle on and off based on the deadband temperature difference. Equipment is usually designed and rated to avoid this condition. Most tankless/instantaneous water heaters modulate.
The volume of the storage tank [m3]. This field is autosizable if used with a Water Heater:Sizing object. Although this field is allowed to go down to zero, even so-called "tankless" water heaters have some volume of water that is maintained around the heating elements or in the heat exchanger, typically around 0.00379 m3 (1 gallon).
The reference to the schedule object specifying the hot water temperature setpoint [°C]. Also known as the "cut-out" temperature.
The delta temperature difference [Δ°C] between the setpoint and the "cut-in" temperature at which the heater will turn on. In other words, the "cut-in" temperature is Setpoint – Deadband.
The temperature [°C] at which the tank water becomes dangerously hot and is vented through boiling or an automatic safety. The tank temperature will never exceed the maximum. Any extra heat added to the tank is immediately vented. Note: The maximum temperature must be greater than the setpoint temperature at all times.
The control type can be Cycle or Modulate. Cycle is appropriate for most storage tank-type water heaters. Modulate is appropriate for most instantaneous/tankless water heaters.
The maximum heat rate [W] that can be supplied to the water, probably the same as the "nominal" capacity. This field is autosizable if used with a Water Heater:Sizing object.
The minimum heat rate [W] that can be supplied to the water. This field is only used when the Heater Control Type is Modulate. If the total demand rate for heating is less than the minimum, even a modulating water heater will begin to cycle.
NOT YET IMPLEMENTED.
NOT YET IMPLEMENTED.
The type of fuel used for heating. The fuel type can be Electricity, NaturalGas, PropaneGas, FuelOil#1, FuelOil#2, Coal, Diesel, Gasoline, Steam, or DistrictHeating.
The thermal conversion efficiency from fuel energy to heat energy for the heater element or burner. This is not the same as the overall efficiency of the water heater.
The reference to the curve object that relates the overall efficiency of the water heater to the Runtime Fraction (if Control Type Cycle) or Part Load Ratio (if Control Type Modulate). This is an additional multiplier applied to the Heater Thermal Efficiency to compute fuel energy use. The Part Load Factor Curve should not have a value less than 0.1 in the domain from 0 to 1. If the Part Load Factor Curve accounts for ambient losses and/or parasitic fuel consumption, these effects should not also be input into the related fields in this object as that would result in double-counting.
Off-cycle parasitics include parts of the water heater that consume fuel when the heater is off, for example, a pilot light, or stand-by electronic control circuits. The fuel consumption rate [W] is strictly the total fuel that is consumed by all of the off-cycle parasitics.
The type of fuel used by the off-cycle parasitics. The fuel type can be Electricity, NaturalGas, PropaneGas, FuelOil#1, FuelOil#2, Coal, Diesel, Gasoline, Steam, or DistrictHeating. The fuel type can be the same or different from the Heater Fuel Type.
The fraction of off-cycle parasitic fuel energy that is converted to heat energy that ends up in the tank water. For example, a pilot light would deliver most of its heat to the tank water, as long as the thermal conversion efficiency must be taken into account, so perhaps 0.80 is reasonable. Electronic control circuits, on the other hand, do not add any heat to the tank and should be 0.
On-cycle parasitics include parts of the water heater that consume fuel when the heater is on, for example, an induction fan, or stand-by electronic control circuits. The fuel consumption rate [W] is strictly the total fuel that is consumed by all of the on-cycle parasitics.
The type of fuel used by the on-cycle parasitics. The fuel type can be Electricity, NaturalGas, PropaneGas, FuelOil#1, FuelOil#2, Coal, Diesel, Gasoline, Steam, or DistrictHeating. The fuel type can be the same or different from the Heater Fuel Type.
The fraction of on-cycle parasitic fuel energy that is converted to heat energy that ends up in the tank water. For example, an induction fan might (maybe) deliver a small fraction of its energy to the tank water for a value of 0.05. Electronic control circuits, on the other hand, do not add any heat to the tank and should be 0.
The Ambient Temperature Indicator specifies how the ambient air temperature will be indicated. The field can be Schedule, Zone, or Outdoors. If Scheduleis used, the Ambient Temperature Schedule field provides the ambient temperature. If ZONE is used, the zone air temperature of the zone specified in the Ambient Temperature Zone field provides the ambient temperature. If EXTERIOR is used, the outdoor dry-bulb air temperature provides the ambient temperature.
The reference to the schedule object specifying the ambient air temperature around the tank for skin losses. This field is only used if Ambient Temperature Indicator is Schedule.
The reference to the zone object specifying the ambient air temperature around the tank for skin losses. This field is only used if Ambient Temperature Indicator is Zone.
This optional alpha field specifies the outdoor air node name used to define the ambient conditions surrounding the water heater tank. This field is applicable only when the Ambient Temperature Indicator is specified as OutdoorAir:Node, otherwise this field should be left blank. The node name specified must also be specified in an OutdoorAir:Node object where the height of the node is taken into consideration when calculating outdoor air conditions from the weather data. Alternately, the node name may be specified in an OutdoorAir:NodeList object where the outdoor air conditions are taken directly from the weather data.
The loss coefficient [W/K] to the ambient air temperature. Often this coefficient is identical to the "UA" for skin losses. However, it can also be used to model the loss effects of the flue in a combustion water heater, in addition to the skin losses.
If the Ambient Temperature Indicator is Zone, this field adds the specified fraction of the off-cycle losses to the zone heat balance as an internal gain.
The loss coefficient [W/K] to the ambient air temperature. Often this coefficient is identical to the "UA" for skin losses. If the loss effects of the flue are being modeled in the Off-Cycle Loss Coefficient, than this field would have a different value accounting only for the skin losses.
If the Ambient Temperature Indicator is Zone, this field adds the specified fraction of the on-cycle losses to the zone heat balance as an internal gain.
The peak flow rate [m3/s] of domestic hot water usage for stand-alone operation, i.e., without plant loop node connections. The peak value is multiplied by the Use Flow Rate Fraction Schedule. If there are node connections, this field is not used.
The reference to the schedule object specifiying the current fraction of Peak Volumetric Use Flow Rate of domestic hot water usage for stand-alone operation.
The reference to the schedule object specifying the cold water temperature [°C] from the supply mains that makes up for the hot water lost down the drain. If blank, water temperatures are calculated by the Site:WaterMainsTemperature object. This field is for stand-alone operation only. If there are node connections, this field is not used.
The inlet node connection to the plant loop for the use side of the water heater. Typically the use side draws hot water from the tank and returns cooler water.
The outlet node connection to the plant loop for the use side of the water heater. Typically the use side draws hot water from the tank and returns cooler water.
This field specifies the heat transfer effectiveness between the use side water and the tank water. If the effectiveness is set to 1 then complete heat transfer occurs, simulating perfect mixing of the use side water and the tank water. If the effectiveness is lower, then the use side outlet water temperature will not be as hot as the tank water, simulating a heat exchanger.
The inlet node connection to the plant loop for the source side of the water heater. Typically the source side draws cold water from the tank and returns warmer water. The source side volume flow rate is obtained from the plant loop. The magnitude of the flow rates through the source side can be controlled by setting the Maximum Branch Flow Rate field in the Branch object that connects the source inlet node.
The outlet node connection to the plant loop for the source side of the water heater. Typically the source side draws cold water from the tank and returns warmer water.
This field specifies the heat transfer effectiveness between the source side water and the tank water. If the effectiveness is set to 1 then complete heat transfer occurs, simulating perfect mixing of the source side water and the tank water. If the effectiveness is lower, then the source side outlet water temperature will not be as hot as the tank water, simulating a heat exchanger.
This field is optional and is used to specify the design flow rate through the Use Side of the water heater. The volumetric design flow rate is specified in m3/s. The field is needed when the Use Side is connected to a plant loop. The field can be autosized. If autosized, then the input file should include a Plant Sizing object for the plant loop. Sizing results are reported in the EIO file.
This field is optional and is used to specify the design flow rate through the Source Side of the water heater. The volumetric design flow rate is specified in m3/s. The field is needed when the Source Side is connected to a plant loop. The field can be autosized. If autosized, then the input file should include a Plant Sizing object for the plant loop. Sizing results are reported in the EIO file.
This field is optional and is used to provide a design parameter for autosizing design flow rates when the water heater is connected to the demand side of a plant loop. The recovery time is expressed in hours. This is the time that the entire volume of the tank can be heated from 14.4ºC to 57.2ºC (58ºF to 135ºF) with an inlet temperature defined as the exit temperature in the associated Plant Sizing object. The default is 1.5 hours. The calculation is based on log-mean temperature difference (LMTD) and includes the heat transfer effectiveness factor entered above.
Note: Additional Help Information under construction.
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