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Servicing should only be performed by a Qualified Service Technician
VARIABLE FREQUENCY DRIVE – SBL85275NE(A) THRU SBL85390NE(A)
The SBL85275NE(A) thru SBL85390NE(A) models have a
variable frequency drive (VFD)
that controls
the speed of the blower motor. The VFD receives a signal from the thermostat and ignition control that
instructs the VFD to transmit the proper frequency to the blower to produce the proper blower speed and
proper input rate.
Two conditions must be met for the variable frequency drive to start the blower at low speed:
1. 100 - 120VAC must be supplied to the VFD input.
2. The thermostat closes a contact through the low speed I/O module – VFD terminals LI1 and +24V.
Summary of Contents for SBL85275NE
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