Dear Everyone,
I wonder of modeling CAV system in Baseline System type 9. My proposed building is storage with thermostat setpiont 12 C ( 54 F) with natural ventilation.
I have 2 cases of Proposed systems.
1. Radiators are used to heat spaces without any fans.
2. Local convective heating devices with fans are used
3. Assume that we have some fresh air supply with DOAS AHU.
AD 1 In first case radiators will operate only when heating is needed. I assume something about 30% of annual time. If I set system 9 CAV how should it operate? If I set availability for whole year I will get huge energy use for fans that will recilculate constant amount of air even when heating is not needed.
AD 2. In such case fans will also operate when needed. I can set them to cycled or stagged. How about the Baseline? Should it also be cycled or stagged?
AD3. In that case when system 9 is CAV does it needs to operate whole year with maximum air? Proposed AHU will operate full year but its energy use will be relative small. For most of the year heating will not be needed.
BTW. This storage is not semiheated space
Many thanks
Tyler Thumma
7GroupLEEDuser Expert
65 thumbs up
October 3, 2019 - 1:46 pm
Any natural ventilation would be modeled identically in the Baseline and Proposed.
The Proposed systems should all be modeled to operate as they are designed. I would assume the radiators and convective heaters would both cycle to meet the thermostat setpoint and the DOAS AHU would operate continuously whenever the space is occupied and turn off when unoccupied.
The Baseline System 9 would be modeled with the minimum outside air required by code, and the fans would run continuously at constant volume on the same schedule as the DOAS AHU fans since they are supplying the outside air. The System 9 heat would cycle as needed to maintain the thermostat setpoint.