Operating Instructions

Chapter 3—Applications for ATEC—VAV with Reheat
3-60 Siemens Building Technologies, Inc.
Fan Operation
CAUTION:
On a terminal box with a series fan, the terminal box fan must be
controlled/interlocked to start either before or at the same time as the
central air handler. Failure to do so may cause the terminal box fan to
rotate backwards and cause consequent damage at start up.
Day Mode—FAN (Point 44) is ON all of the time.
Night Mode—The fan is controlled as follows:
The fan turns on when at least one of the following two conditions has been met:
• The electric heat, HEAT STAGE 1 (Point 43), turns on.
-or-
• The airflow out of the supply duct, FLOW (Point 75), is greater than the setting for
SERIES ON (Point 26).
The fan turns off only when the following two conditions have been met:
• The first stage of electric heat has been off for at least one full duty cycle. (HEAT
STAGE 1 has been OFF longer than STAGE TIME, Point 89).
-and-
• The airflow out of the supply duct, FLOW, is less than the setting for SERIES OFF
(Point 27).
If the conditions have not been satisfied to turn the fan on or off, the state of the fan remains
unchanged. (That is, if the fan is on, it remains on, while if the fan is off, it remains off.)
Fail-safe Operation
If the air velocity sensor fails, the controller uses pressure-dependent control. The
temperature loop controls the operation of the damper.
If the room temperature sensor fails, the controller operates using the last known temperature
value.
Automated Checkout
The ATEC has a built-in checkout procedure that can be manually initiated at any time after
the controller has been installed. The procedure tests all of the necessary I/O and ensures
the controller has the ability to operate within the set airflow range, between CLG FLOW MIN
(Point 31) and CLG FLOW MAX (Point 32).