Delta Controls
Document Edition 4.2
Page 33 of 43
Heating Controller Limiting
Setup variable AV29 is used as a
heating controller limit
. A value of 0 to 100% entered into this
variable will limit the main heating controller accordingly, and by default is set to 100%.
By limiting the controller value itself you are able to limit the output staging, which may be used for
load limiting purposes. However, this limit is only applicable for heating, not cooling applications.
4.
T
RI
-S
TATE OR
F
LOATING
P
OINT
(DNT-T103
O
NLY
)
Tri-State uses a pair of outputs (always Outputs 1 and 2). Output 1 opens the device, and Output 2
closes the device. It is assumed that when neither output is on the device does not change position. The
Tri-State device has a runtime property, the time that it takes to go from fully open to fully closed. It is
assumed that the device will take as long to close as it does to open and that the open and close rate is
linear.
At start up the Tri-State algorithm establishes a closed position reference by closing continuously for
1.25 x the Run Time. It will also enter this state each time that it first receives a zero position valve. A
signal of 100% will cause the algorithm to open the device for 1.25 run times to establish an open
reference.
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.]
