If the q
vmin
and q
vmax
settings restrict the usable control
range, this changes the characteristic profile of the set-
point value signal. Since the signal voltage of the actual
value is always assigned to the characteristic profile of
q
vnom
, this results in a restriction of the usable control
range in a different characteristic profile of the signal
voltages for setpoint and actual values.
In this case, a direct inference due to different signal
voltages at the setpoint value input or actual value
output without (rollover) calculation is not possible.
9.2 Systematic troubleshooting
In case of malfunctions of the VAV terminal unit, we rec-
ommend systematic troubleshooting based on our flow
A ‘Systematic troubleshooting’ on page 44
9.3 Further diagnostic options
9.3.1 Use of voltmeters to control setpoint
values and feedback signals
In analogue mode, a voltmeter can be used to electri-
cally measure both the setpoint value signal Y (terminal
Y to earth) and the actual value signal U (terminal U to
earth). Using the following formulas, the associated
volume flow rate setpoint values and actual value scan
be calculated and thereby checked:
Voltage signal 0 – 10 V
× (q
– q
) + q
q
Y
10 V
=
vmin
vsoll
vmin
vmax
q
× q
U
10 V
vist
vnenn
=
Voltage signal 2 – 10 V
q
×(q
– q
)+q
Y– 2
(10 V– 2 V)
vsoll
=
vmax
vmin
vmin
q
× q
U – 2
(10 V – 2 V)
vist
vnenn
=
Note:
Depending on the selected setting of the q
vmin
- /
q
vmax
values, the setpoint value signal voltage and
actual value voltage can be different even in the cor-
rectly controlled state,
point value and actual value signal’ on page 34
9.3.2 Sample calculations
Example 1:
Calculation of the volume flow rates by means of
setpoint and actual value signal voltage
Terminal unit nominal volume flow
rate q
vnom
- 1828 m³/h
Set q
vmin
- 600 m³/h
Set q
vmax
- 1000 m³/h
Characteristic setting
- 0 – 10 V
Voltage (Y)
- 8.24 V
Voltage (U)
- 5.4 V
× (q
– q
) + q
q
Y
10 V
=
vmin
vsoll
vmin
vmax
Billing solution:
q
vset
= (8.24 V / 10 V)
×
(1000 m³/h – 600 m³/h) +
600 m³/h
q
vset
= 929.6 m³/h
q
× q
U
10 V
vist
vnenn
=
q
vist
= 5.4 V / 10 V
×
1828 m³/h
q
vist
= 987.12 m³/h
Deviation = 987.12 m³/h – 929.6 m³/h
Deviation = 57.52 m³/h
q
vsoll
q
vist
v
×100%
∆q
= 1–
Δ
q
v
= 1 – (929.6 m³/h / 987.12 m³/h)
×
100
Δ
q
v
≈
6%
Troubleshooting
Further diagnostic options > Sample calculations
Control component Compact XM0 • XS0 for VAV terminal unit TVE
35
