Application

Supply Chains for Primary Plants / Room
Supply Chain Coordination - Supply Air: Group Member
66
Siemens Industry, Inc.
Application Note
A6V11692042
Smart Infrastructure – Building Products
2019-04-01
Dual Duct AHU changeover condition signal
Each multistate VAV supply changeover condition input signal
(VavSuChovrCnd1, VavSuChovrCnd2) comes from the room coordinating function
(RCoo). It indicates the current heating / cooling available status for central AHU.
Four states are supported:
1. Neither
2. Heating
3. Cooling
4. Neutral
Default configuration for VAV Dual Duct is Duct 1 is set to ‘cooling’ and Duct 2 is
set to ‘heating’. These can be changed, in defaults, or commanded by central
equipment for each duct
"Neutral" means that heating and cooling PID controllers are both enabled and that
the system is providing air that is not hot or cold.
Configuration
Parameters
Description
Parameter
Pre-loaded Value
Enable deviation calculation
0:No
1:Yes
EnDvnCal
Yes
Enable saturation calculation
0:No
1:Yes
EnStrtnCal
Yes
Saturation level → If the percent open value for damper position (VavSuPos)
is above the Saturation level (StrtnLvl) and the airflow error value (relative
setpoint VavSuSpAflRel minus relative airflow VavSuSpAirFl) is greater than
the Air volume flow error limit (AirFlErLm), the saturation signal
VavSuAflStrtn will be True after DlyOnStrtn time. (If AirFlErLm is left at
default 0%, then the airflow error value has no effect on the saturation
signal.)
StrtnLvl
90%
Air volume flow error limit → In % of Nominal airflow value (AirFlNom);
If the airflow error value (relative setpoint VavSuSpAflRel minus relative
airflow VavSuSpAirFl) is greater than the Air volume flow error limit
(AirFlErLm) and the percent open value for damper position (VavSuPos) is
greater than StrtnLvl, the saturation signal (VavSuAflStrtn) will be True after
DlyOnStrtn time. (If AirFlErLm is left at default 0%, then the airflow error
value has no effect on the saturation signal.)
AirFlErLm
0.0%
Switch-on delay saturation → The minimum length of time a saturation
condition must remain in effect before the saturation signal VavSuAflStrtn
changes to True.
DlyOnStrtn
60.0 secs
Switch-on point for air flow demand → The minimum initial airflow setpoint
value above which the supply chain airflow demand object (VavSuAirDmd)
switches from Off to the current plant operating mode.
SwiOnAirFlDmd
4% (of AirFlNom)
Hysteresis for air flow demand → The percent value below SwiOnAirFlDmd
at which the airflow demand object (VavSuAirDmd) switches from the
current plant operating mode to Off.
HysAirFlDmd
2% (of AirFlNom)
Enable relief
0:No (disables the relief function)
1:Yes (enables the relief function)
EnRlf
No