Technical Instructions LMV Series
Document No. LV3-1000
Section 5 Page 24 SCC Inc.
After these points are considered, the LMV3 parameters can be set for the application.
1. Set the expected amount of speed shift. This can be changed at any point in time, even with the
burner running, so if the exact value is not known a conservative approach (smaller magnitude
number) is recommended. Note that the percentages set here are a percentage of the standardized
speed. For a standardized speed of 3544 RPM, a 4% VSD shift would equate to 141 RPM. On an
LMV36, these shifts can be configured for each fuel.
a. VSD Shift High (increase VSD speed) = parameter 548 for Fuel 0, parameter 568 for Fuel 1
b. VSD Shift Low (decrease VSD speed) = parameter 547 for Fuel 0, parameter 567 for Fuel 1
The range for VSD shift high is 0 to 25%, and the range for VSD shift low is 0 to -15%.
The amount of speed shift is related to the analog signal according to Figure 5-8 below:
Figure 5-8: VSD Speed Shift – Analog Signal to % VSD Trim
Looking at the figure above, 10mA is the neutral point for the VSD shift. A signal of 10mA will
not cause any type of VSD speed shift off of the VSD curve. This neutral point of 10mA is not
adjustable.
The VSD Shift High and the VSD Shift Low are independently adjustable so that they may be
tailored to the application and to the ambient conditions when the fuel-to-air ratio curves are
commissioned.
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