Delta Controls DNS-24, Application Manual

Page: 23 / 43

Delta Controls
Document Edition 4.2 Page 23 of 43
Setup Parameters
Setup Variable Function Notes
AV24 Tri-state Flow Damper Runtime Default of 120 seconds
AV25 Air Flow Factor Converts Duct size and Air flow
velocity to CFM or Liters/Second
AV26 Air Flow Minimum Minimum Air Flow Setpoint
AV27 Air Flow Maximum Maximum Air Flow Setpoint
AV28 PWM minimum value or Binary On Delay (or
Binary Off Delay for a Fan) Depends on OP3 configuration
AV29 PWM maximum value or Time Proportioned
Heating Controller Limit Depends on OP3 configuration
Sequence of Operation
The airflow setpoint is generated from the Cooling Minimum setpoint, Cooling Maximum Setpoint and
the Cool 1 value as shown below.
Air flow Setpoint
Max
Cooling flow
Min
Cooling flow
Controller Output (Cooling 1)
0
Max Flow
0% 100%
The Air Flow input is compared to the current Airflow setpoint by the flow control loop. On the DNT-
T103, the Tri-State damper outputs 1 and 2 are used to control the damper to adjust the flow to match
the current airflow setpoint. The rate of the damper from closed to open is adjusted using AV24 –
Damper Run Time. The default value is 120 seconds. On the DNT-T221, the analog damper output 1 is
used to control airflow, but also requires that an appropriate runtime be set for the actuator (via Setup
variable AV24).
In Unoccupied Deadband mode the Airflow Setpoint is set to zero.
Output 3 may be selected as a fan for fan-powered boxes. Alternatively, the output may be selected to
be Heating 1 or supplementary Cooling 2, which may be of type Binary or PWM or Timed
Proportional.
Variable AV25 (Air Flow Factor) represents a value that includes duct size and any other constants or
conversion factors so Input 2 reads air flow (in CFM or L/S), and requires that:

a 0 to 1” H
2
O (0 to 250 Pa) sensor is connected to Input 2 (AI2); and

the air flow units of either CFM or L/S is selected

AFF = box K factor * Area in in
2
/ 144 [which is then divided by 2.1188 to get L/S, if
desired] (Refer to page 15 for information on Box Mode and Controller Operation)
N
OTE
: To prevent a series fan from
starting backwards, the damper stays
shut in all night modes – it does not
modulate. If heating is required
during the night, a radiant panel can
be used to meet the
Night Heating
Setpoint (AV10). Since the damper
will not modulate for night cooling
(AV11), if night cooling is required
write a GCL program in an
associated DSC controller on the
network to put the box/BACstat into
Occupancy mode and bring on the air
system until the setpoint is achieved.