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Part number 550-142-054/0411
65
GV90+ gas-fired water boiler — Boiler Manual
Figure 75 Integrated boiler control (IBC) sequence of operation — status light indications
STEPS
(After Step 8, the cycle goes back to Step 1)
Call for
Heat?
POWER TSTAT
CIRC
LIMIT PRESS
SWITCH
FLAME
Timing
1. Standby
• Waiting for call for heat
NO
—
2. Call for heat
• Circulator on
YES —
3. Limit circuit
• Limit controls closed
• Block switch contacts closed
• Blower on
YES —
4. Pressure circuit
• Pressure switch contacts closed
• Ignitor glows
YES
30 sec
5. Flame proven
• Gas valve open
• Ignitor remains on
YES
6 sec
6. Limit cycle
• Limit circuit open
• Gas valve closed
• Blower off after postpurge
YES
30 sec
7. Flame outage *
• Flame out
YES —
8. Thermostat satisfied
• Circulator off
• Blower postpurge
• Return to Step 1
NO 30 sec
= ON
= OFF
* If flame is not proven in 4 seconds, boiler recycles 2 times to retry for ignition before going into lockout. Recycle igniter timing
is 30 seconds. Postpurge and prepurge are performed on every cycle. In event of lockout, ignition control will automatically
restore sequence of operation after either:
• 1 hour waiting period.
• Opening and closing of thermostat circuit.
• Removal of 120 VAC power for at least 45 seconds
Start-up (continued)