Technical Instructions LMV Series
Document No. LV3-1000
Section 5 Page 14 SCC Inc.
Results of Standardization Approximate Correction Limits
LMV3 Speed
Signal to VSD (%)
Blower Wheel
Speed (RPM)
LMV3 Signal
to VSD (VDC)
Maximum Signal to
Correct for Low
RPM (VDC)
Minimum Signal
to Correct for
High RPM (VDC)
0
0 0.00
VSD does not control below 10%
5 187 0.50
10 373 1.00 2.5 0.0
15 560 1.50 3.0 0.5
20 746 2.00 3.5 1.0
25 933 2.50 4.0 1.5
30 1119 3.00 4.5 2.0
35 1306 3.50 5.0 2.5
40 1492 4.00 5.5 3.0
45 1679 4.50 6.0 3.5
50 1865 5.00 6.5 4.0
55 2052 5.50 7.0 4.5
60 2238 6.00 7.5 5.0
65 2425 6.50 8.0 5.5
70 2611 7.00 8.5 6.0
75 2798 7.50 9.0 6.5
80 2984 8.00 9.5 7.0
85 3171 8.50 10.0 7.5
90 3357 9.00 10.5 8.0
95
3544 9.50
10.5 8.5
Figure 5-4 (continued): Result of Standardization (2-Pole Blower Motor) and Interpolation
When the burner is in operation, the LMV3 can be programmed to have active, closed-loop control of
the blower motor speed and can compensate for motor slip and other factors within limits. The speed
control signal can be increased to compensate for low blower RPM and decreased to compensate for
high blower RPM. These speed control signal correction limits are also shown in Figure 5-4.
NOTE: The LMV3 will not attempt to correct the blower speed if the internal speed control is
deactivated. This is determined by parameter 661 in the LMV3. If parameter 661 is set to 1, the LMV3
will attempt to correct blower speed back to the standardized baseline using its internal speed
control. If parameter 661 is set to 0, the LMV3 will not attempt to correct blower speed back to the
standardized baseline. In either case, the blower speed will still be monitored by the LMV3.
NOTE: Typically, parameter 661 is set to 1 (LMV3 speed control active) for VFD and is set to 0 (LMV3
speed control deactivated) for PWM Blowers. PWM blowers typically utilize a built in, high scan rate
speed control that is tuned for that specific blower’s characteristics. Typically, the speed control built
into the PWM blowers is utilized instead of the LMV3 speed control for the reasons stated above.
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