The section describes what is printed when Print Psychrometrics is checked in the Print Load Calculations dialog box.
Print Load Calculation Dialog Box
Psychrometrics
An individual Psychrometrics table is printed for each zone selected in the Zone or Room to Print list. If the whole building is selected, a table will be printed for every zone.
The values in this table are taken directly from or calculated based upon values in the various Building Definition commands. The key values are Coil Dew Point, Reheat, and Humidification.
Calculation Month: The month with the highest humidity that is used in the calculation.
Calculation Hour: It is assumed that the highest humidity happens at 4pm. This row is for informational purposes only.
Outside Air
Airflow: The total ventilation airflow for the zone. Includes additional air to account for any air lost due to Return Duct Leakage set in the Zone List command.
Dry Bulb Temperature: Set using the OSA High Dry field for the Calculation Month in the Project Info command.
Wet Bulb Temperature: Set using the OSA High Wet field for the Calculation Month in the Project Info command.
Humidity Ratio: Calculated based upon the Dry Bulb Temperature and Wet Bulb Temperature.
Total Load: The sum of the Sensible Load and Latent Load.
Sensible Load: The sensible ventilation load.
Latent Load: The latent ventilation load.
Return Air at Diffusers
Airflow: The airflow at the return diffusers.
Dry Bulb Temperature: The return air temperature at the diffusers. Set using the Cooling Temperature field in the Zone List command.
Wet Bulb Temperature: The return air wet bulb temperature at the diffusers. Calculated using the Cooling Temperature and Relative Humidity fields in the Zone List command.
Humidity Ratio: The return air humidity ratio at the diffusers. Calculated using the Cooling Temperature and Relative Humidity fields in the Zone List command.
Plenum Load
The plenum row is included if the Plenum Return field is checked in the Zone List command.
Dry Bulb Temperature: The temperature gain in the airflow based upon the Total Load.
Total Load: The load in the plenum. See the Print Cooling Detail section for more information.
Sensible Load: The sensible load in the plenum. There is no latent load, so this value will be the same as Total Load.
Return Duct Leakage
Airflow: The volume of air leaked out of the return ducts. It is replaced with outside air. Set using the Return Duct Air Leakage field in the Zone List command.
Return Duct Temperature Gain
Dry Bulb Temperature: The change in temperature in the air in the return ducts. Set using the Return Duct Temperature Gain field in the Zone List command.
Total Load: The temperature gain converted to Btu/h based upon the return duct airflow.
Sensible Load: The sensible temperature gain converted to Btu/h. There is no latent temperature gain, so this value will be the same as Total Load.
Return Air at Apparatus
Airflow: The return airflow at the piece of mechanical equipment. Includes any loss due to Return Duct Leakage set in the Zone List command.
Dry Bulb Temperature: The return air temperature at the mechanical equipment. Equal to the sum of Return Air at Diffusers: Dry Bulb Temperature, Plenum Load: Dry Bulb Temperature, and Return Duct Temperature Gain: Dry Bulb Temperature.
Wet Bulb Temperature: The return air wet bulb temperature based upon the calculated Dry Bulb Temperature and the Return Air at Diffusers: Humidity Ratio.
Humidity Ratio: The return air humidity ratio at the piece of mechanical equipment. The dry bulb temperature change does not affect the amount of moisture in the return air, so this value will be the same as Return Air at Diffusers Humidity Ratio.
Mixed Air
Airflow: The sum of the Outside Air: Airflow and Return Air at Apparatus: Airflow.
Dry Bulb Temperature: The average of the Outside Air: Dry Bulb Temperature and Return Air at Apparatus: Dry Bulb Temperature, weighted by their relative airflow volumes.
Wet Bulb Temperature: Calculated based upon the Dry Bulb Temperature and Humidity Ratio.
Humidity Ratio: The average of the Outside Air: Humidity Ratio and Return Air at Apparatus: Humidity Ratio, weighted by their relative airflow volumes.
Fan (Blow Through)
This row is included if the Fan Position field is set to Blow Through in the Zone List command.
The Fan Brake Horsepower set in the Zone List command is displayed in the row label.
Dry Bulb Temperature: The rise in temperature based upon the Mixed Air: Airflow and Total Load.
Total Load: The load from the fan based upon the Fan Brake Horsepower set in the Zone List command.
Sensible Load: The sensible load from the fan. There is no latent load, so this value will be the same as Total Load.
Motor (In Airstream)
This row is included if the Motor Position field is set to In Airstream and Fan Position field is set to Blow Through in the Zone List command.
The Motor Efficiency set in the Zone List command is displayed in the row label.
Dry Bulb Temperature: The rise in temperature based upon the Motor Efficiency and Fan Brake Horsepower set in the Zone List command.
Total Load: The temperature gain converted to Btu/h based upon the Mixed Air: Airflow.
Sensible Load: The sensible temperature gain converted to Btu/h. There is no latent temperature gain, so this value will be the same as Total Load.
Motor (Out of Airstream)
This row is included if the Motor Position field is set to Out of Airstream and Fan Position field is set to Blow Through in the Zone List command.
Coil Entering Air
This row is included if the Fan Position field is set to Blow Through in the Zone List command.
Airflow: The same value as the Mixed Air: Airflow.
Dry Bulb Temperature: The air temperature right before it enters the coil. The sum of the Mixed Air: Dry Bulb Temperature, Fan: Dry Bulb Temperature, and Motor: Dry Bulb Temperature.
Wet Bulb Temperature: Calculated based upon the Dry Bulb Temperature and Humidity Ratio.
Humidity Ratio: The same value as the Mixed Air: Humidity Ratio.
Coil Dew Point
Airflow: The volume of air that passes over the coil. Equal to Mixed Air: Airflow minus Coil Bypass Air: Airflow.
Dry Bulb Temperature: The dew point temperature that corresponds to the Humidity Ratio.
Wet Bulb Temperature: The same value as the Dry Bulb Temperature.
Humidity Ratio: The humidity ratio needed for the design conditions of the rooms in the zone. Calculated based upon the Airflow, Coil Bypass Air values, and Supply Air at Diffusers values.
Coil Bypass Air
Airflow: The volume of air that is not conditioned by the coil. Equal to Mixed Air: Airflow multiplied by Coil Bypass Factor set in the Zone List command.
Dry Bulb Temperature: The temperature is the same as the Mixed Air: Dry Bulb Temperature or Coil Entering Air: Dry Bulb Temperature, depending upon the Fan Position setting.
Wet Bulb Temperature: The wet bulb temperature is the same as the Mixed Air: Wet Bulb Temperature or Coil Entering Air: Wet Bulb Temperature, depending upon the Fan Position setting.
Humidity Ratio: The humidity ratio is the same as the Mixed Air: Humidity Ratio or Coil Entering Air: Humidity Ratio, depending upon the Fan Position setting.
Coil Leaving Air
Airflow: The volume of air that leaves the coil. Equal to Mixed Air: Airflow.
Dry Bulb Temperature: The average of the Coil Dew Point: Dry Bulb Temperature and Coil Bypass Air: Dry Bulb Temperature, weighted by their relative airflow volumes.
Wet Bulb Temperature: Calculated based upon the Dry Bulb Temperature and Humidity Ratio.
Humidity Ratio: The average of the Coil Dew Point: Humidity Ratio and Coil Bypass Air: Humidity Ratio, weighted by their relative airflow volumes.
System Load
Total Load: The total system cooling load for the zone.
Sensible Load: The sensible system cooling load for the zone.
Latent Load: The latent system cooling load for the zone.
Reheat
Dry Bulb Temperature: Equal to the AHU and Coil Settings, Cooling Temperature field set in the Zone List command minus the Coil Leaving Air: Dry Bulb Temperature.
Humidification
Humidity Ratio: Equal to Supply Air at Diffusers: Humidity Ratio minus Coil Leaving Air: Humidity Ratio.
Fan (Draw Through)
This row is included if the Fan Position field is set to Draw Through in the Zone List command.
The Fan Brake Horsepower set in the Zone List command is displayed in the row label.
Dry Bulb Temperature: The rise in temperature based upon the Coil Leaving Air: Airflow and Total Load.
Total Load: The load from the fan based upon the Fan Brake Horsepower set in the Zone List command.
Sensible Load: The sensible load from the fan. There is no latent load, so this value will be the same as Total Load.
Motor (In Airstream)
This row is included if the Motor Position field is set to In Airstream and Fan Position field is set to Draw Through in the Zone List command.
The Motor Efficiency set in the Zone List command is displayed in the row label.
Dry Bulb Temperature: The rise in temperature based upon the Motor Efficiency and Fan Brake Horsepower set in the Zone List command.
Total Load: The temperature gain converted to Btu/h based upon the Coil Leaving Air: Airflow.
Sensible Load: The sensible temperature gain converted to Btu/h. There is no latent temperature gain, so this value will be the same as Total Load.
Motor (Out of Airstream)
This row is included if the Motor Position field is set to Out of Airstream and Fan Position field is set to Draw Through in the Zone List command.
Supply Duct Leakage
Airflow: The volume of air leaked out of the supply ducts. Set using the Supply Duct Air Leakage field in the Zone List command.
Supply Duct Temperature Gain
Dry Bulb Temperature: The change in temperature in the air in the return ducts. Set using the Return Duct Temperature Gain field in the Zone List command.
Total Load: The temperature gain converted to Btu/h based upon the return duct airflow.
Sensible Load: The sensible temperature gain converted to Btu/h. There is no latent temperature gain, so this value will be the same as Total Load.
Supply Air at Diffusers
Airflow: The supply airflow required to condition the zone. This value is the same as the Required Supply CFM column in the Supply Air Requirements table. See the Print Supply Air Requirements section for more information.
Dry Bulb Temperature: Set using the AHU and Coil Settings, Cooling Temperature field in the Zone List command.
Wet Bulb Temperature: Calculated based upon the Dry Bulb Temperature and Humidity Ratio.
Humidity Ratio: The humidity ratio is the same as the Coil Leaving Air: Humidity Ratio.
Room Load
Humidity Ratio: Calculated based upon the Latent Load and Supply Air at Diffusers Airflow.
Total Load: The total room cooling load for the zone.
Sensible Load: The sensible room cooling load for the zone.
Latent Load: The latent system room load for the zone.
Final Room Conditions
Dry Bulb Temperature: Set using the Indoor Air Defaults, Cooling Temperature field in the Zone List command.
Wet Bulb Temperature: Calculated based upon Indoor Air Defaults, Cooling Temperature and Indoor Air Defaults, Relative Humidity fields in the Zone List command.
Humidity Ratio: Calculated based upon Indoor Air Defaults, Cooling Temperature and Indoor Air Defaults, Relative Humidity fields in the Zone List command.