Application

Application Notes
Dual Duct Sequence Configurations
16
Siemens Industry, Inc.
Application Note
A6V11692055
Smart Infrastructure – Building Products
2019-04-01
Use Case 3a – VAV DD with ventilation in both ducts, cold duct ventilation in deadband, snap
acting control:
Cold duct will stay open in deadband to
meet ventilation requirement. On an exit to
heating, the cold duct closes immediately
and the hot duct takes over ventilation
needs.
Ducts may close if ventilation requirement
goes to zero.
Parameter configuration for use case 3a:
• VavSuChovrCnd1 = Cooling
• VavSuChovrCnd2 = Heating
• VntDuctSprt = Both ducts
• CtlStrgy = Snap acting control
• VntSprtDdband = Duct 1
In use case 3a, with the thermal load in deadband the cold duct air flow will equal the current value of the ven-
tilation flow demand (may vary per room operating mode or DCV); the hot duct air flow will be zero.
On an increase in cooling load, the 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.
On an increase in heating load, the cold duct closes and the hot duct will open (snap action) to take over any
active ventilation flow rate. 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.