Lmv5 Will Not Modulate Properly - Siemens LMV5 Series Technical Instructions

Technical Instructions
Document No. LV5‐1000
1. Ensure that the LMV5 is in automatic mode through the following menu path:
ManualOperation > Autom/Manual/Off = Automatic
2. Check the PID settings and make sure that they are set for the application.
P‐Part – This is the proportional band. The proportional band increases firing rate based on
how far below setpoint the temperature / pressure is. Smaller values cause a more
aggressive response to a drop in pressure / temperature relative to setpoint. Values that
are too small will cause hunting. Typical setting: 10% to 30%.
I‐Part – This is the integral part, which serves to eliminate steady state "droop" caused by
the proportional band setting. Thus, this works hand in hand with P‐Part to bring the
pressure / temperature up to setpoint. Smaller values cause a more aggressive response (a
setting of 1 is most aggressive). Values that are too small will cause overshoot. Typical
setting: 80 sec to 300 sec. A setting of 0 deactivates the feature, but this is not
recommended.
D‐Part – This is the derivative part, which serves to eliminate overshoot, and allows a more
aggressive integral setting. Larger values cause a more aggressive response. D‐Part is not
needed on many steam boilers. If needed, small values of less than 20 typically work well.
A setting of 0 deactivates the feature. Large values will typically cause hunting.
3. Check the load limit parameters (UserMaxLoad, MinLoad, MaxLoad) to verify that they are
not limiting modulation.
4. Check the load mask parameters under each fuel and verify that they are not preventing
modulation. These can be checked using the following menu path:
Params & Display > RatioControl > Gas/Oil Settings > LoadLimits
Default values are: LoadMaskLowLimit = 0%, LoadMaskHighLimit = 0%.
5. If the LMV5 goes to high fire in phase 52, check parameter StartPointOp under each fuel.
This should typically be set to 1 (low fire).
Note: If PID values are set properly, the load should change no more than once every 8
seconds on most installations. If PID values are set improperly, the duty cycle of the SQM...
actuator can be exceeded.
Section 7
LMV5 Will Not Modulate Properly
Page 12
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