Application

Application Notes
Dual Duct Sequence Configurations
13
Siemens Industry, Inc.
Application Note
A6V11692053
Smart Infrastructure – Building Products
2019-04-01
On an increase in heating load, the heating flow demand on the hot duct modulates from heating flow min to
heating flow max. Cold duct air flow will be the value of the difference between hot duct air flow and the cur-
rent ventilation flow demand, provided that the ventilation flow demand is greater than hot duct air flow, oth-
erwise cold duct air flow will be zero.
Use Case 2b – VAV DD with ventilation in both ducts, hot duct ventilation in deadband, with mixing con-
trol:
Hot duct will stay open in deadband to meet
a ventilation requirement. As cooling load
ramps up, hot duct damper modulates to
zero as cold duct damper modulates open
(i.e., mixing control during ramp up of cool-
ing mode).
Ducts may close if ventilation requirement
goes to zero.
Parameter configuration for use case 2b:
• VavSuChovrCnd1 = Cooling
• VavSuChovrCnd2 = Heating
• VntDuctSprt = Both ducts
• CtlStrgy = Mixing control
• VntSprtDdband = Duct 2
In use case 2b, 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 cooling flow demand on the cold duct modulates from cooling flow min to
cooling flow max. Hot duct air flow will be the value of the difference between cold duct air flow and the cur-