LME Series Technical Instructions
Document No. LME-1000
SCC Inc. Page 5 Section 6
Commissioning the LME7 when Using a PWM Blower
After verifying that all PWM blower-related components are installed and wired correctly, the LME7
burner control can be programmed for the PWM blower application.
Prerequisites
• Ensure that the PWM blower is a closed loop type, meaning that it is utilizing an onboard speed
control properly tuned for that specific blower.
• Ensure that the maximum closed loop speed that the PWM blower is programmed for is adequate
for the application.
• Ensure the wiring is correct, paying particular attention to the low voltage wiring. Some PWM
blowers have their electronics internally powered from the high voltage, while others require
separate, external low voltage power.
After these points are double-checked, the LME7 parameters can be set for the application.
1. Set the blower ramp times.
a. Ramp up = Parameter 522
b. Ramp down = Parameter 523
These ramp times should be set at least 10% longer than the capabilities of the connected PWM
blower. For example, if the PWM blower can ramp up in 20 seconds, then parameter 522 should be
set to at least 22 seconds. The same logic applies for the ramp down, parameter 523.
2. Set the maximum speed of the PWM blower via parameter 519. This should be copied directly from
the blower nameplate or otherwise provided by the blower manufacturer.
3. Set the number of pulses per revolution for the PWM blower tachometer speed feedback signal via
parameter 644. This should be provided by the blower manufacturer and is typically only found in
the blower technical literature.
4. Set parameter 559 to activate or deactivate the LME7 internal speed control. For PWM blowers,
especially those utilizing a properly tuned onboard speed control, parameter 559 is typically set to 0.
Setting the value to 0 turns off the speed control inside the LME7 and allows the speed control to be
performed solely by the PWM blower.
5. Set the PWM blower speed monitoring bands to values that are safe for the application. These are
set via parameters 650.00 and 650.01. See complete explanation of these bands detailed earlier on
pages 3 and 4.
6. Set the standby speed of the PWM blower via parameter 503.00. This is typically set to 0 RPM.
7. Set the prepurge and postpurge speed of the PWM blower via parameter 503.01. This is often set at
the same value as the high fire speed (P2).
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