Internal Loads
Internal loads typically have a significant impact on the cooling load of a building. The internal loads library category allows you to create and manage the necessary loads that will be applied to rooms and zones in the building.
There are three types of internal loads:
People
These library members are created to define the heat gain from occupancy. They are applied to the zones in the room properties screen. TRACE™ 3D Plush has standard library members that include typical occupancy densities from NREL and heat gain per activity type per ASHRAE HOF 2013. The people library member details screen displays the fields that must be defined:
Density
Defines the amount of people in a given zone. It can be defined as a total number of people, an amount of area per person (i.e. sq•ft/person) or an amount of people per area (People/sq•m).
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Default Value: Per NREL table 4 Occupancy by space type
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Typical Range: 1 to 5,000
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Min & Max: 0 to 50,000
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Units: number of people; ft2/person; m2/person; people/sq•ft; people/m2
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Activity
Defines the activity level being performed by the people in the zone. It determines the amount of heat gain per person in the zone under design conditions. The available options are taken from the ASHRAE Handbook of fundamentals 2013, chapter 18.
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Default Value: Per ASHRAE HOF 2013
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Typical Range: N/A
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Min & Max: N/A
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Units: N/A
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Sensible Load
Is the amount of sensible heat added to the space by the occupants. Each activity will have an associated sensible load. This value can be overridden by the user if desired.
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Default Value: Per ASHRAE HOF 2013
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Typical Range: 0 to 640 Btuh/person; 0 to 187 W
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Min & Max: 0 to 2000 Btuh; 0 to 586 W
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Units: Btuh; W
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Latent Load
Is the amount of latent heat added to the space by the occupants. Each activity will have an associated latent load. This value can be overridden by the user if desired.
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Default Value: Per ASHRAE HOF 2013 depending on the Activity type
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Typical Range: 0 to 1,000 Btuh/person; 0 to 293 W
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Min & Max: 0 to 2000 Btuh; 0 to 586 W
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Units: Btuh; W
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Sensible Radiant
Defines the amount of the total sensible heat given off by people that is radiant. The remainder of the sensible load is assumed to be convective heat gain.*
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Default Value: 0.6
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Typical Range: 0 to 1
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Min & Max: 0 to 1
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Units: %
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Lights
These library members are created to define the heat gain from internal lighting. They are applied to the zones in the room properties screen. TRACE™ 3D Plus has standard library members that include typical lighting densities and heat gains. Lights Library has two groups created: 90.1 Building Area Method and 90.1 Space Type Method. All other lights libraries are displayed to the right of those groups and more can be added or grouped. The lights library member details screen displays the fields that must be defined for each lights library member standard libraries have information from ASHRAE or from manufacturers:
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Power
Defines the design lighting density. It can be defined as a total number of watts in the zone, lighting power per zone floor area (i.e. W/sq. ft.) or lighting power per person (i.e. w/person).
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Default Value: Per ASHRAE HOF 2013 depending on the space type
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Typical Range: 0.5 to 2 W/sq•ft; 5.38 to 21.5 W/m2
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Min & Max: 0 to 100000
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Units: W; W/ft2 ; W/m2; w/person; w/fixture
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Number of Fixtures
This field is only available when the units for the Power is w/fixture. It acts as a direct multiplier of the Power selected on the previous field.
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Default Value: 1
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Typical Range: Depends on the zone
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Min & Max: 1 to 999,999
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Units: N/A
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Lighting Configuration
Defines the luminaire type as defined per Chantrasrisalai, C., and D.E. Fisher. 2007.
Heat into Return Air
The percent of the heat from lights that goes into the zone return air. If the return air flow is zero or the zone has no return air plenum, this load will be put into the zone air. Enter the value as a decimal.*
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Default Value: Depending on the lighting configuration
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Typical Range: 0 to 0.5
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Min & Max: 0 to 1
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Units: %
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Thermal Radiation
The percentage of heat from lights that goes into the zone as long-wave (thermal) radiation. The program will calculate how much of this radiation is absorbed by the inside surfaces. Enter the value as a decimal.*
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Default Value: Depending on the lighting configuration
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Typical Range: 0.01 to 0.22
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Min & Max: 0 to 1
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Units: %
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Visible Radiation
The fraction of heat from lights that goes into the zone as visible (short-wave) radiation. The program calculates how much of this radiation is absorbed by the inside surfaces. Enter the value as a decimal.*
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Default Value: Depending on the lighting configuration
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Typical Range: 0.01 to 0.2
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Min & Max: 0 to 1
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Units: %
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Note: The total sum of the Return Air Fraction From Plenum Temperature, Thermal Radiation, and Visible Radiation percentages must be 100% or less.
Miscellaneous Equipment
These library members are created to define the heat gain from various plug loads. They are applied to the zones in the room properties screen. TRACE™ 3D Plus has standard library members that include typical miscellaneous load densities and heat gains. These loads are categorized by fuel type:
Electric, Steam, and Other Equipment
Heat Gain
Defines the design maximum input to the equipment. It can be defined as a total number of watts or Btu, load per zone floor area or load per person.
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Default Value: Per ASHRAE HOF 2013 depending on the equipment type
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Typical Range: N/A
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Min & Max: -10,000,000 to 10,000,000
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Units: %
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Latent
The amount of latent heat given off by the miscellaneous load. It affects the moisture balance within the zone. Enter the value as a decimal.
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Default Value: 0
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Typical Range: 0 to 1
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Min & Max: 0 to 1
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Units: %
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Radiant
The amount of long-wave radiant heat being given off by the miscellaneous load. This value is multiplied by the total energy consumed by the load to give the amount of long wavelength radiation gain. Enter the value as a decimal.
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Default Value: 0
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Typical Range: 0.1 to 0.2
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Min & Max: 0 to 1
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Units: %
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Lost Heat
The amount of heat which is “lost” and does not impact the zone energy balances. It might correspond to energy converted to mechanical work or heat that is vented to the atmosphere. Enter the value as a decimal.
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Default Value: 0
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Typical Range: 0 to 1
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Min & Max: 0 to 1
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Units: %
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Note: The total sum of the Latent, Radiant and Lost Heat percentages must be 100% or less.
Gas Equipment
Gas Equipment has an additional field.
Carbon Dioxide Generation Rate
Is the contaminant rates for gas equipment in the zone. Enter the CO2 generation rate per unit of power. Enter zero for equipment that is fully vented. A suggested value for non-vented equipment would be 3.45E-8 m3/s*W converted from a natural gas CO2 emission rate of 117 lbs. CO2 per million Btu.
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Default Value: 0
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Typical Range: 0 to 3.45E-8 m3/s•W
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Min & Max: 0 to 2.48439651E-04 cfm/Btuh; 0 to 0.0000004 m3/s•W
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Units: cfm/Btuh; m3/s•W
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Hot Water Equipment
Hot water equipment has three additional fields.
Peak Flow Rate
The peak demanded hot water flow rate. It can be defined as a total flow rate, a flow rate per floor area or flow rate per person.
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Default Value: 0
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Typical Range: -10,000,000 to 10,000,000
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Min & Max: -10,000,000 to 10,000,000
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Units: gpm, gpm/person, gpm/ft2; m3/s, m3/s/person, m3/s/m2
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Entering Water Temperature
The supply hot water temperature at the tap.
Leaving Water Temperature
The leaving cold water temperature.
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Default Value: 0
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Typical Range for entering: 32 to 150°F; 0 to 66°C
Typical Range for leaving: 80 to 220°F; 26 to 94°C
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Min & Max: 32 to 200°F; 0 to 100°C
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Units: °F; °C
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IT Equipment
IT equipment has four additional fields.
Electric Consumption
The design maximum input to the IT equipment when fully loaded. It can be defined as the number of watts per unit or watts per area or load per person.
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Default Value: Per ASHRAE HOF 2013 depending on the equipment type
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Typical Range: N/A
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Min & Max: -10,000,000 to 10,000,000
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Units: W, W/ft2, W/m2; W/person, Btu, Btu/ft2, Btu/m2 , Btu/person
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Number of Units
The total number of units that have the electric consumption from the previous field.
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Default Value: 1
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Typical Range: N/A
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Min & Max: 0 to 10,000,000
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Units: N/A
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Account only for energy use
This checkbox allows the ability to select in the project if a miscellaneous load will only spin the meter and will not add any load to the space.
Modeling Method
This field only allows you to select in the project if a Miscellaneous Equipment will only spin the meter or if it will add a load to the space. The options are:
Load: The Miscellaneous Equipment will only bring a load to the space without spinning the meter.
Load and Energy: The Miscellaneous Load will add a load to the space and will spin the energy meter. This option is only available for full licenses and if the Operating Mode selected is Energy and Economics.
Energy: The Miscellaneous Load will only spin the energy meter. This option is only available for full licenses and if the Operating Mode selected is Energy and Economics.