7
Troubleshooting
Volume flow rate controllers with Easy controller are
tested technically before delivery. Operating parameters
must be set individually for each controller during com-
missioning to the required system conditions.
If faults occur after commissioning, they can usually be
remedied yourself using the following descriptions.
If a fault cannot be remedied on its own, TROX Service
will be happy to assist you with troubleshooting, simply
‘TROX Technical Service’ on page 3
For this, the following information is needed:
Type and nominal size of VAV terminal unit (see
adjustments sticker):
Vmin/Vmax settings
Control input signal
7.1 Common mistakes
7.1.1 Volume flow rate deviation due to
unfavourable installation situation
If the desired volume flow rate value is not adhered to
precisely enough, which is the most frequent cause of
error, this creates an unfavourable installation situation
of the VAV terminal unit.
If the straight inflow length upstream of the volume flow
controller is too short, the airflow becomes turbulent and
the measurement of the volume flow rate becomes inac-
curate. This is especially true when installing behind
sharp edged bridges, fittings or junctions. The neces-
sary straight inflow lengths are specified in the installa-
tion and commissioning instructions of the VAV terminal
unit.
7.1.2 Incorrect wiring
In many cases wiring errors are the cause of faults. For
this reason, only the 24 V supply voltage should initially
be connected when troubleshooting an volume flow
controller.
1.
If present, disconnect the connecting cables at the
setpoint value input (terminal w) and the actual
value output (terminal U). This switches off all
external circuit influences.
2.
Check if the 24 V supply voltage is switched on.
ð
When the supply voltage is switched on, the
Easy controller attempts to set the volume flow
rate to the setpoint value V
min
.
3.
Check whether the controller has reached the set-
point value.
The green LED must light up solid within approx.
180 seconds. In addition, the signal voltage of the
actual value output (terminal U) can be measured
with a multimeter,
ð
If the setpoint value is reached, the controller
will work properly.
4.
The test can be repeated for different setpoint
values by adjusting the V
min
potentiometer.
7.1.3 System pressure too low
The aim of the volume flow control is to regulate the
volume flow rate actual value to the specified setpoint
value.
For this purpose, a larger volume flow rate is required in
the duct, which can be controlled (throttled) with the
controller to the desired setpoint value.
If the volume flow rate in front of the control unit is too
low (required minimum differential pressure not avail-
able), the setpoint value cannot be reached.
This can be detected on the damper blade shaft of the
VAV terminal unit.
If the damper blade is still in the OPEN position with the
setpoint signal present, instead of in a control position
(throttle position), the volume flow rate is not high
enough to set the setpoint value. The controller will try
to open the damper blade further to reach the desired
volume flow rate setpoint value.
7.1.4 Use outside the control area
If the device-specific control range is left with the poten-
tiometer setting V
min
/V
max
, or with the specified setpoint
signal, the setpoint values cannot be reached. The
actual value reached by the controller is undefined.
Potentiometer adjustment and setpoint value control
signal:
Depending on the control unit type, the voltage signal
must be >1V or 2V, in particular, when setting V
min
= 0%
and V
max
= 100%, in order to control the valid control
range.
Additional Information:
Chapter 6.1.1 ‘Control ranges of VAV terminal
Chapter 3.6 ‘Characteristics’ on page 16
7.1.5 Deviation between setpoint value
and actual value signal
Frequently, in the regulated state of the Easy controller,
the same signal voltage is expected at the setpoint
value input and the actual value output. However, this
only applies in the event that a V
min
of 0% and a V
max
of
100% are set on the potentiometers, since the same
characteristic curve vertices are used for the setpoint
value input and the actual value output.
Furthermore, in the controlled state, due to the permis-
sible control tolerance, small deviations between the
signal voltages of the setpoint value and actual value
can always be expected.
Troubleshooting
Common mistakes > Deviation between setpoint value and actual value signal
Control component Easy for VAV terminal units
26
