7 Troubleshooting
Air terminal units with Easy controller are tested techni-
cally before delivery
. During commissioning, the oper-
ating parameters must be set individually to the required
system conditions for each controller.
If faults occur after commissioning, they can usually be
remedied using the following descriptions.
If you cannot remedy a fault yourself, TROX Service will
be happy to assist you with troubleshooting. Simply con-
tact
Ä
‘TROX Technical Service’ on page 3
The following information is required for this purpose:
Type and nominal size of VAV terminal unit (see
adjustment sticker):
q
vmin
/ q
vmax
settings
Control input signal
7.1 Common faults
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 a
fault, this equates to an unfavourable installation situa-
tion of the VAV terminal unit.
If the straight inflow length upstream of the air terminal
unit is too short, the airflow becomes turbulent, and
measurement of the volume flow rate becomes inaccu-
rate. This is especially true when installing behind sharp
edged bridges, fittings or junctions. The necessary
straight inflow lengths are specified in the installation
and commissioning instructions of the VAV terminal unit.
7.1.2 Incorrect wiring
Faults are often caused by wiring errors. For this
reason, only the 24 V supply voltage should initially be
connected when troubleshooting a volume flow rate
controller.
1. If present, disconnect the connecting cables at the
setpoint value input (terminal w) and the actual
value output (terminal U). This switches of
f 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 q
vmin
.
3. Check whether the controller has reached the set-
point value.
The green LED must light up solidly within approx.
180 seconds. In addition, the signal voltage of the
actual value output (terminal U) can be measured
with a voltmeter
,
Ä
29
ð
If the setpoint value is reached, the controller
will work properly.
4. The test can be repeated for dif
ferent setpoint
values by adjusting the q
vmin
potentiometer.
7.1.3 System pressure too low
The aim of volume flow control is to regulate the volume
flow rate actual value to the specified setpoint value.
Sufficient output by the fan is therefore needed so that
the desired nominal volume flow rate can be set (throt-
tled) with the control unit.
If the output is too low (required minimum differential
pressure not available), 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 range
The setpoint values cannot be reached, if the device-
specific control range is not maintained with potentiom-
eter setting q
vmin
/q
vmax
or with the specified setpoint
signal. The actual value reached by the controller is
undefined.
Checking the potentiometer setting and setpoint value
signal:
Depending on the control unit type, the voltage signal
must be >1 V or 2 V, in particular, when setting q
vmin
=
0% and q
vmax
= 100% to actuate the valid control range.
Additional information:
Ä
Chapter 6.1.1 ‘Control ranges of VAV terminal
units’ on page 22
Ä
Chapter 3.6 ‘Characteristics’ on page 16
7.1.5 Deviation between setpoint value
and actual value signal
In the regulated state of the Easy controller
, the same
signal voltage is often expected at the setpoint value
input and actual value output. However, this only applies
if q
vmin
0% and q
vmax
100% are set on the potentiome-
ters, since the same characteristic curve vertices are
used for the setpoint value input and actual value
output.
Furthermore, in the controlled state small deviations
between the signal voltages of the setpoint value and
actual value can always be expected because of the
permissible control tolerance.
Troubleshooting
Common faults > Deviation between setpoint value and actual va...
Easy control component for VAV terminal units26
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