Belimo NMV-D2M, Руководство пользователя

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43
4A
1P
C
-T
V2
.1
NM
V
-D2
M
-EN
11
-02
-04.
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P
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VAV
– Module NMV-D2M
Sequence
- Reference signal hunting
- Volumetric flow following the setpoint
- Damper hunting in the control range
N-P1.9 VAV-Box
............................................................................................................
unstable reference signal
Suggestions for improvements
Match the reference control circuit correctly and adapt
the controller parameters (P-band, etc.) to suit the
complexity of the plant.
Investigate the positioning of the room temperature
sensor. Mounting (e.g. tension from the conduit),
draughts, sun, etc. can have a direct effect on the
quality of control.
Suitable Test-Sequences
-
Test 2 Max-Auto 6m.txt
-
Test 3 Max-Auto-Min 9m.txt
-
Record the symptom with ‘Live Trend’ over an extended period of time,
e.g. overnight. This allows intermittent faults to be located more easily.
Note:
The Test-Sequence is discontinued because of the lack of system
supply pressure.
Fault alarm: ‘Inadequate supply air pressure’ is given.
Cause and consequence
Room temperature control circuits are usually slow-
response control loops: A tendency to hunt is an
indication of either a lack of settings or incorrect set-
tings.
The VAV controller follows the reference signal, which
is its task. Therefore, when a system is hunting it
means that the damper actuator is in constant motion.
So an adverse effect on service life is an inevitable
consequence.
Pressure control is affected and, as a result, also the
remaining VAV-boxes in the same section.
N-P1.10 VAV-Box
................................................................................
unsuitable reference signal <-> Mode
S A D
A
Sequence
a)
Step 1 + 3: V’max / V’min
Function correct
b) Step 2: Auto (reference input active)
- DDC output, room controller: 5.0 V
- NMV-D2M regulates to 245 instead of 275 m
3
/h
c) Step 2: Auto (reference input active)
- DDC output, room controller: 0.0 V
-
Damper closes completely instead of to V’min
Suggestions for improvements
a) Change over the NMV-D2M to the 0...10 V mode,
or
b) Change over the DDC output, room controller to
working range 2...10 V (if this is possible).
Suitable Test-Sequences
- Test 2 Max-Auto 6m.txt
-
Test 3 Max-Auto-Min 9m.txt
Note:
If the system does not attain the required supply pressure
– during the
test start
– the Test-Sequence is discontinued and the fault alarm ‘In-
adequate supply air pressure’ is given.
Naturally, the opposite situation can also arise: ‘DDC 2...10 V, NMV-
D2M 0...10 V’.
In this case the result is a worse deviation in the
V’min range.
Cause
- The external reference signal (DDC, room tempera-
ture controller) has a working range of 0...10 V
- The NMV-D2M is is set to 2...10 V mode
Function: 0 V = Close
2...10 V
= V’min...V’max
The NMV-D2M is closed completely by the 0 V sig-
nal instead of to the required V’min
(see c) .
a b c
S
A D
A
a
NMV-D2M
– Diagnosis
Legend
Legend