Siemens LMV5 Quick Start Manual page 138

Fan speed not reached or Control range limitation VSD Module
Typically, if the LMV52 / VFD / Motor standardize successfully this system will operate correctly.
However, if the standarization is successful but problems are encountered during burner operation,
consider the following:
1) Ramp times. Faster ramp times on both the VFD and the LMV52, create a more demanding
application for the VFD. Simply put, a faster ramp time (20 seconds instead of 40 seconds)
will cause the VFD to draw or absorb much more amperage for a given change in blower
speed, since the change in speed occurs more quickly.
Ramp times that are faster than the VFD can handle can lead to over current faults on the
VFD as well as error messages on the LMV52 stating "Fan speed not reached" or "Control
range limitation VSD Module".
Increasing ramp times typically helps these problems.
Please see the next point for details on these two most common LMV52 error messages.
2) If "Fan speed not reached " or "Control range limitation VSD Module" frequently appear on
the AZL5, this indicates that the LMV52 has shifted the 0 / 4-20mA as far as possible from
the standardized signal and the RPM of the blower motor as read by the speed wheel is still
to low or too high.
"Fan speed not reached" indicates that the blower speed is still to low,
even though the LMV52 has increased the 0 / 4-20mA signal as far as possible.
This shows up as a warning on the AZL5 for the first 2 seconds,
and if it the blower speed does not increase in this time a lockout will occur.
Conversely, "control range limitation VSD Module" indicates that the blower speed is too
high even though the LMV52 has decreased the 0 / 4-20mA signal as far as
possible.
This also shows up as a warning on the AZL5 for about 5 seconds,
and if the blower speed does not decrease in this time a lockout will occur.
If "Fan speed not reached" occurs when the blower is ramping up,
and "control range limitation VSD Module" occurs when the blower is ramping down,
there is a good chance that the VFD is not able to accelerate or decelerate
the blower wheel quickly enough for the given ramp times.
As was previously mentioned, extending the ramp times will help this situation.
3) Inertia of the rotating assembly (blower motor wheel and motor armature).
As the mass and inertia of the blower wheel and motor armature increase,
the power needed to accelerate (increase RPM) and decelerate (decrease RPM) increases.
Large blower motors connected to large heavy blower wheels,
typically require longer ramp times and / or VFD with high over current capability,
so that "Fan speed not reached" or "Control range limitation VSD Module" lockouts
do not occur.
4) The alarm input into the LMV52 from the VFD.
The LMV52 has an alarm input terminal from the VFD,
so that if the VFD is having a problem, the LMV52 can sense this and shut the burner down.
If an Error code A9 Diagnostic code 0C is encountered,
then this means that the VFD caused the LMV52 to alarm by energizing terminal
X73.3 on the LMV52 with 24 VDC.
Typically, this happens due to an over current in the VFD itself.
LMV5 QSG Rev 4 Sec 5 Pg 12 www.scccombustion.com