Vii-Wiring And Sequence Of Operation - Lennox ML196DFE Series Unit Information

VII-WIRING DIAGRAM AND SEQUENCE OF OPERATION
1 - Line voltage is applied to L1 and N. the T1 low voltage transformer is energized, and line voltage is applied to B3 indoor blower.
2 - S47 rollout switch(es) must be closed in order for 24V from transformer to be output on integrated control "R" to power thermostat.
3 - When there is a call for heat, W1 of the thermostat energizes W of the furnace control with 24VAC.
4 - A92 integrated control runs a self-check. S10 primary limit and S21 secondary limit contacts are found to be closed. Call for heat can continue.
5 - A92 integrated control energizes B6 combustion air inducer. S18 combustion air pressure switch closes . Once S18 closes, a 15-second pre-
purge follows.
6 - A92 integrated control energizes R33 ignitor. A 20-second warm-up period begins.
7 - GV1 gas valve opens for a 4-second trial for ignition
8 - Flame is sensed, gas valve remains open for the heat call.
9 - After 30-second delay (from flame sensed), A92 integrated control applies 24VAC to Heat speed of B3 indoor blower.
10- When heat demand is satisfied, W1 of the indoor thermostat de-energizes W of A92 integrated control which de-energizes GV1 gas valve. B6
combustion air inducer continues a 5-second post-purge period, and B3 indoor blower completes a selected OFF time delay.
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