# Heating Device - Gas Boiler

## System

### Nominal Thermal Efficiency

Specify the Nominal Thermal Efficiency, a necessary numeric field indicating the heating efficiency (as a fraction between 0 and 1) of the boiler's burner. This efficiency is relative to the higher heating value (HHV) of fuel at a part load ratio of 1.0.

### Boiler Flow Mode

Specify the Boiler Flow Mode, a crucial choice field determining the operational behavior of the boiler concerning intended fluid flow. Choose from "Not Modulated," suitable for variable or constant speed pumping arrangements with the boiler making nominal flow rate requests, "Constant Flow," ideal for constant speed pumping arrangements with stricter flow rate requests, and "Leaving Setpoint Modulated," altering the boiler model to internally vary the flow rate to match the leaving temperature to a setpoint. Note that external plant system operations can influence flow through the boiler. The default, if unspecified, is "Not Modulated."

### Min. Part Load Ratio

Specify the Min. Part Load Ratio is a numeric field defining the minimum part load ratio. This ratio influences the operating ratio if the demand-to-boiler nominal capacity ratio falls below it. The expected range is 0 to 1, and the default value is 0.0 if left unspecified.

### Max. Part Load Ratio

Specify the Max. Part Load Ratio is a numeric field indicating the maximum part load ratio. If the ratio of demand to boiler nominal capacity exceeds this value, the Max PLR determines the operating part load ratio. The typical range is between 0 and 1.1, with a default value of 1.0 if left blank.

### Water Outlet Upper. Temp. Limit

Specify the Water Outlet Upper Temp. Limit, a numeric field indicating the upper limit for the outlet temperature. If left blank, the default value is 99.9ºC.

### Parasitic Electric Load

Specify the Parasitic Electric Load, an optional numeric field representing the parasitic electric power (W) consumed by devices associated with the boiler, such as a forced draft fan. This load operates whenever the boiler is in use, and the model assumes it doesn't contribute to heating the water. The minimum value is 0.0, and the default is also 0.0 if left blank.

## Sizing

### Hot Water Loop Pump Rated Power Consumption

Specify the Hot Water Loop Pump Rated Power Consumption, a numeric field for the pump's design power consumption in Watts.

### Hot Water Loop Pump Rated Flow Rate

Specify the Hot Water Loop Pump Rated Flow Rate, a numeric field for the pump's design maximum volume flow rate in cubic meters per second.

### Hot Water Loop Pump Min. Flow Rate

Specify the Hot Water Loop Pump Min. Flow Rate is a field containing the minimum volume flow rate during variable flow capacity rate operation in cubic meters per second. When set to autosize, the input field Design Minimum Flow Rate Sizing Factor scales the minimum flow rate as a fraction of the Design Maximum Flow Rate.

### Sizing Factor

Specify the Sizing Factor, an optional numeric field allowing users to specify a sizing factor for autosized component design inputs. This factor scales the autosizing calculations, allowing users to meet part of the design load while using the autosizing feature.

### Sizing Method

Specify the Sizing Method, offering a choice between Autosize or Manual. Manual sizing requires completion of all numerical fields with valid entries.

### Design Water Flow Rate

Specify the Design Water Flow Rate, a numeric field indicating the maximum design water volumetric flow rate in m3/sec, representing the largest flow rate that can be heated.

### Nominal Capacity

Specify the Nominal Capacity, a numeric field containing the nominal operating capacity in watts (W) of the boiler. If autosized, a heating plant sizing object is necessary.

### Hot Water Pump

### Pump Speed Control

Specify the Pump Speed Control by choosing between Variable Speed or Constant Speed for the hot water pump.

### Pump Rated Head

Specify the Pump Rated Head in Pascals to set the pump head pressure for the hot water pump.

### Pump Design Min. Flow Rate Fraction

Specify the Pump Design Min. Flow Rate Fraction to determine that the minimum flow rate is set as the product of this sizing factor and the Design Maximum Flow Rate.

### Pump Motor Efficiency

Specify the Pump Motor Efficiency by entering a numeric value, representing the pump motor's efficiency in decimal form (0 = 0%, 1 = 100%).

### Pump Control Type

Specify the Pump Control Type by choosing from Continuous or Intermittent. In the case of a variable speed pump, it is defined with maximum and minimum flow rates. If there is no load on the loop and the pump operates intermittently, it can shut down. For other conditions, such as the loop having a load, the pump operates intermittently or continuously, adjusting the flow between the minimum and maximum limits to meet the flow request from demand side components.

### Pump Fraction of Motor Inefficiencies to Fluid Stream

Specify the Pump Fraction of Motor Inefficiencies to Fluid Stream by entering a numeric value, indicating the pump motor's fraction of power loss to the fluid.

### Pump Design Power Sizing Method

Specify the Pump Design Power Sizing Method by choosing between Power Per Flow and Power Per Flow Per Pressure. If Power Per Flow is selected, the pump's Design Power Consumption will be calculated (Power Consumption = Design Maximum Flow Rate * scaling factor) using the sizing factor from the input field Design Electric Power per Unit Flow Rate.

If Power Per Flow Per Pressure is chosen, the calculation (Design Power Consumption = Design Maximum Flow Rate * Design Pump Head * scaling factor / Motor Efficiency) uses the sizing factor from the input field Design Shaft Power per Unit Flow Rate Per Unit Head.

### Pump Design Elec. Power / Flow Rate / Pressure

Specify the Pump Design Elec. Power / Flow Rate / Pressure when the Design Power Consumption is set to autosize, and the Design Power Sizing Method is Power Per Flow Per Pressure. This input allows you to set the efficiency of the impeller and drive assembly when calculating the pump power consumption for the design flow rate, motor efficiency, and pump head. If omitted, the default value of 1.282051 W/((m³/s)-Pa) will be used.

### Pump Design Elec. Power / Flow Rate

Specify the Pump Design Elec. Power / Flow Rate when the Design Power Consumption is set to autosize, and the Design Power Sizing Method is Power Per Flow. This input allows you to set the efficiency of the pumping system's power consumption using only the design flow rate. If omitted, the default value of 348701.1 W/(m³/s) will be used.

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