Lennox LGH150S - DIRECT DRIVE BLOWER SEQUENCE OF OPERATION; TROUBLESHOOTING; Blower Operation:; Blower Fault Sequence Direct Drive Motor - No S52:; Blower Fault Sequence Direct Drive Motor - With S52 (If Configured):

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LGH/LCH092-152U STAGED SUPPLY AIR, DIRECT DRIVE BLOWER
Direct Drive EBM Blower Motor: The blower speed is deter
mined by thermostat demand and settings programmed into
the A55. When A55 receives a Y1 demand, a low speed volt
age output from A55 terminal 4 will energize B3 in low speed.
When A55 receives a Y2 demand, a high speed voltage output
from A55 terminal 4 will energize B3 in high speed. A55 output
voltage can be checked between A55 terminals 4 and 6.