Central Systems in loadmodeling.tool have optional Central Components, which include steam humidifiers (electric, natural gas) and preheat coils (hydronic, DX heat pump, electric, natural gas). Each central component option has a unique set of inputs, described below.


Central Humidifier - Natural Gas

  • Rated Power - The nominal full output power consumption of the unit in watts, exclusive of the blower fan power consumption and any standby power. Defaults to Autosized.

  • Rated Capacity - The nominal full output water addition rate of the unit. Defaults to Autosized.

  • Thermal Efficiency - The thermal efficiency of the gas-fired humidifier. The thermal efficiency is based on the higher heating value of the fuel. A typical value is 0.8.


Central Humidifier - Electric

  • Rated Power - The nominal full output power consumption of the unit, exclusive of the blower fan power consumption and any standby power. Defaults to Autosized.

  • Rated Capacity - The nominal full output water addition rate of the unit. Defaults to Autosized.


Preheat Coil - Hydronic

  • Entering/Leaving Air Temp [°F (IP) | °C (SI)]: The entering and leaving air temperatures of the coil. The default Inlet temperature is read from the Winter Design Day

  • Entering/Leaving Fluid Temp [°F (IP) | °C (SI)]: The entering and leaving fluid temperatures of the coil. By default these are assigned per the Heating Source Mechanical Plant.

  • Rated Capacity [Btu/h (IP) | Watts (SI): The heating capacity of the coil at the rated inlet and outlet air and water temperatures. The gross rated heating capacity does not account for the effect of supply air fan heat. Default is Autosized, however the value can be manually assigned.

  • Heating Source: The Mechanical Plant acting as the heat source for this coil. For version 2 of the platform, this is fixed as an Ideal Heating Loop


Preheat Coil - DX Heat Pump

  • Entering Air Temperature [°F (IP) | °C (SI)]: The design inlet air temperature. Defaults to Autosized.

  • Leaving Air Temperature [°F (IP) | °C (SI)]: The outlet air condition desired for design flow. Defaults to Autosized.

  • Rated Capacity [Btu/h (IP) | Watts (SI): Defines the total, full load gross heating capacity of the DX coil unit at rated conditions. The gross total heating capacity should not account for the effect of supply air fan heat.

  • Heating COP: The gross rated heating coefficient of performance of the heat pump.

  • Minimum Outdoor Air for Operation: The minimum outdoor temperature below which the heating coil is disabled.


Preheat Coil - Electric

  • Entering Air Temperature [°F (IP) | °C (SI)]: The design inlet air temperature. Defaults to Autosized.

  • Leaving Air Temperature [°F (IP) | °C (SI)]: The outlet air condition desired for design flow. Defaults to Autosized.

  • Rated Capacity [Btu/h (IP) | Watts (SI)]: This is the maximum capacity of the coil. This controlled coil will only provide the needed capacity to meet the control criteria whether it is temperature or capacity controlled. Defaults to Autosized.

  • Heating Efficiency: This is user-inputted efficiency (decimal units, not percent) and can account for any loss. In most cases for the electric coil, this will be 1.0.


Preheat Coil - Natural Gas

  • Entering Air Temperature [°F (IP) | °C (SI)]: The design inlet air temperature. Defaults to Autosized.

  • Leaving Air Temperature [°F (IP) | °C (SI)]: The outlet air condition desired for design flow. Defaults to Autosized.

  • Rated Capacity [Btu/h (IP) | Watts (SI)]: This is the maximum capacity of the coil. This controlled coil will only provide the needed capacity to meet the control criteria whether it is temperature or capacity controlled. Defaults to Autosized.

  • Heating Efficiency: This is user-inputted efficiency (decimal units, not percent) and can account for any loss. In most cases for the natural gas coil, this will be 0.8-0.85.

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