I.
Power to unit
1. Door switch must be closed
2. Transformer energized
II. Thermostat Call for Fan Only (R-G)
1. Fuse must be closed
2. Blower safety limit must be closedIII. Thermostat Call
for Heat (R-W)
1. Fuse must be closed
2. Blower safety limit must be closed
3. Power vent relay energized on board
A. Power vent relay contacts close
on board
1. Power
vent motor starts
a. Pressure switch closes
1. 15 second timer built into board to prove air flow.
4. Hot surface ignitor relay energized on board.
A. Hot surface ignitor is
energized.
5. Gas Valve energized after 17 second delay.
A. Rollout switches, high limit
switch and stack overtemp switch must be closed.
6. Flame sensor allows 7 seconds to prove flame.
After 3 tries and no flame a 1 hour lockout occurs. Lockout can
can be overridden by turning the
unit off for more that 2 seconds and back on again.
7. Indoor blower motor starts 30 seconds after proof of
flame.
IV. Thermostat Satisfied
1. Gas Valve shuts extinguishing flame.
2. Vent motor continues to run for 29 seconds (post purge)
3. Blower continues to run for 150 seconds.
Ignition Control Board (ICB) Self diagnostic light signals. Blinks
1. If any of the
safety limits are open the light will blink 4 times
2. If the vent pressure switch is closed before the vent
motor even starts the light will blink 2 times
3. If the pressure switch does not close after the vent
motor starts the light will blink 3 time.
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