Fan:OnOff
Used in:
- Fan Coil Unit
- PTAC,
- PTHP,
- Unitary Heat Cool,
- Unitary Heat Pump
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Used in:
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The On/off fan models a constant air volume fan that is intended to cycle on and off in tandem with a cooling or heating system (i.e., AUTO fan control mode). The fan can also operate continuously like a Constant volume fan. If modelling continuous operation and this object is used as part of a system that utilizes Coil:Heating:Gas, Coil:Cooling:DX:SingleSpeed or Coil:Heating:DX:SingleSpeed, the user should confirm proper air flow rates (coil and fan max load fraction is less than or equal to 1 for all values of coil part-load ratio).
Multi-speed fan operation can also be modelled when the On/off fan is included as part of a compound object that allows multiple fan speeds (e.g.,Unitary Heat Cool, PTAC, etc.). In this case, the ratio of the compound object air flow rate to the fan’s maximum air flow rate is used to determine the power at alternate fan speeds. The input for Fan Power Ratio Function of Speed Ratio Curve Name must be entered to model multi-speed fan operation. An optional fan total efficiency ratio curve is also available to model efficiency differences at alternate fan speeds.
A unique system assigned name for an instance of an On/off fan. Any reference to this fan by another object will use this name.
The ratio of the power delivered to the fluid to the electrical input power. It is the product of the motor efficiency and the fan efficiency. The motor efficiency is the power delivered to the shaft divided by the electrical power input to the motor. The fan efficiency is power delivered to the fluid (air) divided by the shaft power. The power delivered to the fluid is the mass flow rate of the air multiplied by the pressure rise divided by the air density. Must be between 0 and 1.
The pressure rise (in Pascals or ftH2O) at full flow and standard (sea level) conditions (20°C and 101325 Pa).
The required pressure rise across an AHU fan is dependent on the duct network supplied by the AHU. For example, if a duct network was sized using a constant pressure loss of 1 Pa/m and the index run of the network (route of highest pressure drop) was say 300 m and the fitting losses were say an additional 20%, the required pressure rise across the fan would be 300 x 1 x 1.2= 360 Pa.
Allows you to specify a user-defined end-use subcategory, e.g., "Central System", etc. A new meter for reporting is created for each unique subcategory (ref: Report Meter). Subcategories are also reported in the ABUPS table. If this field is omitted or blank, the fan will be assigned to the "General" end-use subcategory.
The full load air volumetric flow rate (m3/sec or ft3/min) at standard temperature and pressure (dry air at 20°C dry-bulb). EnergyPlus uses local barometric pressure to account for altitude using equation for "standard atmospheric" pressure on p 6.1 of the ASHRAE 1997 HOF (SI edition) to initialize the air systems being simulated.
p=101325*(1-2.25577E-05*Z)**5.2559
where p=pressure in Pa and Z=altitude in m
The shaft power divided by the electrical power consumed. Must be between 0 and 1.
The fraction of the motor heat that is added to the air stream. A value of 0 means that the motor is completely outside the air stream. A value of 1 means that all of the motor heat loss will go into the air stream and act to cause a temperature rise. Must be between 0 and 1.
Select an Exponent Performance curve. This curve is used to simulate multi-speed fan motors, representing the ratio of actual fan power to rated fan power when a change in fan speed occurs.
Enter the name of a Quadratic or Cubic Performance curve. This curve is used to simulate multi-speed fan motors, representing the ratio of actual fan total efficiency to rated fan total efficiency when a change in fan speed occurs.
Select the Schedule that defines whether the fan can run during a given time period. A schedule value greater than 0 (usually 1 is used) indicates that the fan can be on during a given time period. A value less than or equal to 0 (usually 0 is used) denotes that the fan is off.
HVAC,Average,Fan Electric Power[W]
HVAC,Average,Fan Delta Temp[C]
HVAC,Sum,Fan Electric Consumption[J]
HVAC,Average,On/Off Fan Runtime Fraction
This output field contains the average electricity consumption rate for the fan in Watts for the timestep being reported.
This output field contains the average rise in air temperature across the fan (outlet air temperature minus inlet air temperature) (in °C or °F)elsius for the timestep being reported.
This output field contains the electricity consumption of the fan in Joules for the timestep being reported. This output is also added to a report meter with Resource Type = Electricity, End Use Key= Fans, Group Key= System (ref. Report Meter).
This output field contains the fraction of time that this fan operated for the timestep being reported