9
Troubleshooting
TROX air terminal units and control components are
tested technically before delivery. The factory-set oper-
ating parameters are documented on the adjustment
sticker and must be checked during commissioning
‘Adjustment sticker’ on page 27
.
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:
Order number and item or serial number (see order
code)
Type and nominal size of VAV terminal unit (see
adjustment sticker):
q
vmin
/ q
vmax
settings
Control input signal
9.1 Common mistakes
9.1.1 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 a control compo-
nent.
1.
If present, disconnect the connecting cables at the
setpoint value input (terminal Y) 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
and is within the permitted tolerance zone.
ð
When the supply voltage is switched on and
there is an adequate minimum differential
pressure in the duct, the control component
attempts to adjust the volume flow rate to the
setpoint value q
vmin
.
3.
Check whether the volume flow controller has
reached the setpoint value.
Reading out with service tool or voltage signal
9.3.1 ‘Use of voltmeters to control setpoint
values and feedback signals’ on page 35
.
ð
If the setpoint value is reached, the volume
flow controller will work properly.
4.
The test can be repeated for different setpoint
values by adjusting the V
min
value.
9.1.2 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. However, this requires a sufficient fan output so
that the terminal unit can regulate (restrict) the desired
volume flow rate setpoint value. If the required minimum
differential pressure is not reached due to an inade-
quate fan output, the setpoint value of the terminal unit
cannot be reached either.
If the system pressure is too low, the volume flow con-
troller will attempt to open the damper blade further to
reach the desired volume flow rate setpoint value. This
can be detected on the damper blade shaft of the VAV
3.2 ‘Position of the damper blade’
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.
Remedy:
Check fan output,
Check if the duct section is blocked, e.g., fire
damper closed
A ‘Systematic troubleshooting’ on page 44
9.1.3 Use outside the control range
If the unit-specific control range is left with the q
vmin
- /
q
vmax
setting, the setpoint values cannot be reached.
The actual value reached by the volume flow controller
is undefined.
Adapt the settings for q
vmin
and q
vmax
with the specific
control ranges of the terminal unit.
Additional information:
Useful control range 4% – 100% of q
vnom
(see
adjustment sticker)
3.5 ‘Characteristics’ on page 15
9.1.4 Deviation between setpoint value
and actual value signal
Frequently, in the regulated condition, the same signal
voltage is expected at the setpoint value input and the
actual value output of the control component. However,
this only applies if q
vmin
is set to 0 m³/h and q
vmax
is set
to q
vnom
, 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 va...
Control component Compact XM0 • XS0 for VAV terminal unit TVE
34
