DNT-T103 & DNT-T221 Application Guide
Page 32 of 41
Document Edition 4.1
The Algorithm estimates the position of the Tri-state device by mapping run time against desired
percent open/closed. Therefore it is important to enter an accurate runtime parameter. The algorithm
also has an internal dead band of 6% to minimize hunting of the valve position.
If a reverse acting valve is to be used, cross connect the Open and Close outputs.
5.
F
AN
C
ONTROL
There are three modes of operation:
Fan Type
Occupied Mode
Unoccupied Mode
Continuous Fan
O
N
constantly.
O
N
when the Controller is not in
deadband for night setback.
Intermittent Fan
O
N
when the Controller is not in
deadband. O
FF
in deadband.
O
N
when the Controller is not in
deadband for night setback.
Manual Fan
Fan O
N
and O
FF
controlled by user
button presses.
O
N
when the Controller is not in
deadband for night setback.
If Fan is selected it is always connected to Output 3, and can be configured for reverse or direct acting.
Setup variable AV28 is the Fan delay value in seconds, which is used for ‘delay off’. [In some cases the
fan should be connected to OP1 and configured as the 1st stage of heating, not as a fan – see the note
below.]
Each configuration has a specific sequence of operation that is tailored to control that type of terminal
unit.
The fan is single speed O
N
/
O
FF
control. With the limited number of outputs, neither the DNT-T103 nor
the DNT-T221 support 2 or 3 speed fans in any of the built-in control strategies. If you need to control a
FCU or other equipment with multi-speed fans, you will need to connect the BACstat to a LINKnet
network, disable local control applications and write your own fan control program in the DAC the
BACstat is connected to.
When the application is set to FCU on a DNT-T103 and the fan type is
Intermittent
, the fan will start
when the first stage controller value for heating or cooling becomes greater than 99.9%. When the first
stage controllers for heating and cooling both become less than 1% and the
Output 3 Binary Delay
(AV28) has timed out, the fan output will be turned off. [Only exists in Release 2 Firmware and higher.]
When the application is set to HPU on a DNT-T103 and the fan type is
Intermittent
, the fan will start
when the compressor starts. When the compressor stops and the
Output 3 Binary Delay
(AV28) has
timed out, the fan output will be turned off. [Only exists in Release 2 Firmware and higher.]
N
OTE
: For fan-powered boxes series fans should always be configured for continuous
operation – never intermittent or the fan could run backwards on startup. And, in order for
a parallel fan to be properly sequenced it should generally be configured as the 1st stage of
heating (and wired to OP1), rather than as a fan.
6.
A
NALOG
(DNT-T221
O
NLY
)
Only the DNT-221 supports two analog outputs, which provide a 0 to 10v signal. Selecting Outputs 1
&2 as analog are not even options in the Configuration Menu for the DNT-T103.
For VAV and VVT, Output 1 is configured as an analog damper (flow for VAV and cooling for VVT).
The other analog output may be configured as a modulating output for auxiliary heating or cooling. Due
to the internal controller logic, an analog flow damper also requires that an appropriate runtime be set
for the actuator (via Setup variable AV24), which is set to control the speed with which the damper will
move and needs to be equal to or greater than the actual run time of the analog actuator. Analog outputs
for auxiliary heating or cooling do not have an associated runtime setting.
