STRA-14 Room controller. Installation and maintenance manual.
Fläkt Woods
8710 GB 2016.09.08
7 (12)
Specifications are subject of alteration without further notice.
CO
2
control
Fläkt Woods STRZ-18-1-1 is an active CO
2
detector
(0-10V). This accessory provides the functionality that the
controller changes step by step from the normal nozzle
setting if required. The nozzle setting is increased when
the ppm level is in excess of the parameter 112 value
(500 ppm) and reaches the maximum nozzle setting
(parameter 305) when the ppm level is in excess of
paramater 113 (1000 ppm). Heating/cooling control (PI)
is preformed simultaneously with the CO
2
control and if
a cooling or heating need occurs the signal is directed to
respectively output (UO1 and UO2). Parameter 81 should
be set to 5 in order to activate the CO
2
function.
Cooling
In control state Cooling, the unit is always a cooling
controller and controls according to the basic cooling
setpoint plus the setpoint displacement.
Cooling/Cooling
Split output signal
In control mode Cooling/Cooling, the controller always
functions as a cooling controller and controls according to
the basic cooling setpoint plus the setpoint displacement.
When the controller output signal reaches 50%, it is
divided between two actuators. 0…48% of the signal is
sent to actuator 1 and 52…100% of the signal is sent to
actuator 2. See the figure below.
Free cooling
In normal operation, the cooling sequence prioritize to
use water cooling, ie output UO2 where the water cooling
valve is connected. If not the water cooling is enough to
reach the set point, the airflow is increased step by step
by opening larger nozzles through UO3. Thus cooling
sequence is divided in 2 step, 0-50% is water cooling
and 51-100% is air cooling. Sometimes you got free
cooling by air, if outside temperature is cooler than the set
point room temperature. Then the STRA-14 can shift the
sequence so that 0-50% is air cooling and 51-100% is water
cooling. This is adjusted by changing the parameter 309.
309=0 Free cooling off – Water cooling 0-50% and 51-100%
air cooling
309=1 Free cooling on – Air cooling 0-50% and 51-100%
water cooling
Free cooling can also be turned on and off through
modbus communication.
Actuators
STRA-14 can be used with two types of actuators:
• Analogue 0…10 V actuators
• Thermal actuators
The actuator type is set via the parameter menu in the
display (parameter 20 and 21). Note that an adapter might
be needed if another actuator than Fläkt Woods STRZ-71
is used.
Analogue actuators
The following output signals can be set for analogue
actuators:
• 0…10 V (F5)
• 2…10 V
• 10…2 V
• 10…0 V
Thermal actuators
When thermal actuator control has been selected, this
is controlled digitally with time proportional pulses
via output UO…. By pulsing, the opening degree of the
actuator (and its valve) is varied. The period time (in
seconds) is the sum of the on and off. The period time is
FS=60s. The controller varies the on and off output times
proportionally depending on the output signal demand to
the actuator.
Actuator exercise
All actuators are exercised. The exercise takes place at
set intervals in hours (FS=23 hours interval). An opening
signal is sent to the actuator for as long time as the run
time has been configured. Then a closing signal is sent for
as long time and the exercise is finished.
Condensation detector
Special input CI
There is a special input (CI) on STRA-14 controllers.
This input is intended for Fläkt Woods’s condensation
detector, STRZ-16, and functions internally as a digital
input, I. e. condensation or no condensation.
When the condensation detector is activated, the cooling
control is blocked and the controller is set in neutral
position. When condensation ceases, the controller will
start controlling from the neutral position.
Window Contact
When the window contact has been configured, the
regulator is set to normal operation when window is
closed. If the window is open, the regulator is set in mode
off, heating and cooling outputs are set to 0 V and the
frost protection function is activated.
