Trace 700 Displacement Ventilation

The folks at Trane CDS Support have some suggestions for compelling Trace 700 to do displacement ventilation modeling:

• The air in a space supplied by an underfloor system is stratified and you only need enough airflow to handle the temperature (loads) in the lower stratified region. Trace (as well as the rest of the simulation programs) assumes well mixed spaces with the same temperature at all locations.
  
• They way to handle this is to model the lower portion (the bottom 6 ft or so) as the height in the space. The top portion is then modeled by calling it a plenum space (plenum of about 5 or 6 feet). Then create custom miscellaneous loads and assign a portion of them to the plenum. The same thing can be done with the lights.
• As for the system side, choose a Constant Volume Variable Temperature system. Go to the Temp/Humidity tab and assign a Leaving Cooling Coil Min and Max temperature of 55°F. Under the Direct/Indirect Humidification Controls, select "CV Mixed Air Bypass with Wild Coil Leaving Temp".
• This will cause the temp off the coil to be low dewpoint, then air will be bypassed around main cooling coil and reintroduced and mixed back in after the main CC, which will allow the air to be supplied to the space with a reasonable %RH at a higher temperature (60-65°F).