Application

Supply Chains for Primary Plants / Room

Supply Chain Coordination - Supply Air: Group Member

Siemens Industry, Inc.

Application Note

A6V11692053

Smart Infrastructure – Building Products

2019-04-01

Supply Chain Coordination - Supply Air: Group

Member

Airflow deviation signal

When the deviation calculation is enabled, a determination is made if the setpoint

is greater than the air flow for a period of time an analog deviation value is mode

available to the central function for additional control logic or reporting.

The supply airflow deviation signal (VavSuAirFlDvn) is used for fan speed (static

pressure) reset strategies at the air handling unit. It is obtained by measuring the

airflow from the supply duct and comparing it to the airflow setpoint.

VavSuAirFlDvn (in percent) = VavSuSpAflRel minus VavSuAirFlRel

VavSuAirFlDvn will equal 0 in case of invalid condition

Dual Duct Saturation signal

When the saturation level calculation is enabled, a determination is made if the

VAV box is starved (damper open greater than the saturation level value, i.e. not

sufficient air ) or satisfied. After saturation conditions are met (time delay

DlyOnStrtn), the saturation signal, VavSuAflStrtn1, VavSuAflStrtn2 is set to True

(starved) and can be shared via grouping with the central function to provide

additional control such as AHU static pressure reset.

Each saturation signal (VavSuAflStrtn1 and VavSuAflStrtn2) is a binary object

that is True ("Starved") when the air flow control loop cannot get enough air to

reach setpoint for a time exceeding a built-in time delay. After the delay expires,

open loop operation begins.

NOTE:

VavSuAflStrtn1/2 is always off if parameter EnStrtnCal = 0 (No). This allows the

user to exclude a particular terminal from the saturation pressure reset system.

Relief input signal

A VAV box’s binary air flow relief object (VavSuAirFlRlf) can be set to True by the

air handling unit. This is done to relieve flow resistance in the duct system in order

to maintain proper static pressure. The VAV controller responds by increasing its

air flow setpoint (VavSuSpAirFl).

When device mode = control mode and both EnRlf (Enable relief) and

VavSuAirFlRlf equal On, VavSuSpAirFl will be set to the maximum of either its

current value or the parameter AirFlRlf.

NOTE:

Relief has no effect on the supply chain VAV air demand signal VavSuAirDmd.