HVAC tab in model data under Mechanical Ventilation header - Compact HVAC
In Compact Unitary HVAC systems the supply fan has two different possible operating modes. The choices for this field are:
For most commercial buildings, continuous fan operation will continue to supply outside air to the zones as typically required by code. For continuous fan operation, the System Availability Schedule is the supply fan operating schedule. For systems where the supply fan only runs when either cooling or heating needs to be supplied to the zone such as for many residential systems, cycling should be specified.
Enter the pressure rise at full flow and standard conditions. Standard conditions are considered 20°C at sea level, 101325 Pa.
See also Calculating Fan Pressure Rise.
Enter the product of the fan motor and impeller efficiency of the supply fan. This is the ratio of the power delivered to the air to the electrical input power at maximum flow expressed as a percentage. 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 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 greater than 0 and less than or equal to 100.
Enter the percentage 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 100 means that all of the motor heat will go into the air stream and act to cause a temperature rise. Must be between 0 and 100.
The calculations for fan power and airflow temperature pick up are detailed in the EnergyPlus Engineering Document. A summary is provided below:
Total Fan Power = Mass flow rate. DeltaP / (Total fan efficiency . Air density)
Shaft Fan Power = Motor efficiency . Total Fan Power
Heat to air = Shaft Fan Power + (Total Fan Power - Shaft Fan Power) . Motor in air fraction