Application

Application Notes
Dual Duct Sequence Configurations
17
Siemens Industry, Inc.
Application Note
A6V11692042
Smart Infrastructure – Building Products
2019-04-01
Use Case 3b – VAV DD with ventilation in both ducts, hot duct ventilation in deadband, snap
acting control:
Hot duct will stay open in deadband to meet
ventilation requirement. On an exit to cool-
ing, the hot duct closes immediately and the
cold duct takes over ventilation needs.
Ducts may close if ventilation requirement
goes to zero.
Parameter configuration for use case 3b:
• VavSuChovrCnd1 = Cooling
• VavSuChovrCnd2 = Heating
• VntDuctSprt = Both ducts
• CtlStrgy = Snap acting control
• VntSprtDdband = Duct 2
In use case 3b, with the thermal load in deadband the hot duct air flow will equal the current value of the venti-
lation flow demand (may vary per room operating mode or DCV); the cold duct air flow will be zero.
On an increase in heating load, the heating flow demand on the hot duct modulates from heating flow min to
heating flow max. Hot duct air flow will be the greater of vent demand and heating demand. Cold duct air flow
will be zero.
On an increase in cooling load, the hot duct closes and the cold duct will open (snap action) to take over any
active ventilation flow rate. Cooling flow demand on the cold duct modulates from cooling flow min to cooling
flow max. Cold duct air flow will be the greater of vent demand and cooling demand. Hot duct air flow will be
zero.