LCD INSTALLATION AND OPERATION INSTRUCTIONS
Page 25
Demand Satisfi ed:
1. When the demand for heat is satisfi ed the operator
switch will open, de-energizing relay R8, TD1, TD3,
TD4, the FSM, and the pilot, main and safety
solenoid valves. The pilot and main flames are
extinguished.
2. The blower delay timer TD3 starts the 80 second
post-purge timing. The blower(s) shut(s) off when
TD3 times out.
3. The pump delay timer TD4 starts the post-purge
timing. The pump(s) remain on for 0.1 to 10 minutes
then shut(s) off when TD4 times out.
High Limit, Low Water Flow, Low Gas Pressure, High
Gas Pressure, Power Venter Interlock Faults
1. Electrical power to the gas valves, blower(s) and
optional power venter will be interrupted if any safety
is tripped.
2. The manual reset high limit can be reset by
depressing the reset button on the left jacket
panel.
Low Air (Blocked Flue/Air Inlet)
• The pressure switch will monitor blower airfl ow.
• Air monitoring will begin at pre-purge. If a low air
condition is present power will not be supplied to the
FSM. The blower(s) will remain on.
OPERATION SEQUENCE, 2 STAGE
OPTION L600 through L2300
Note: Refer to the wiring diagram included with the
unit for further control system info.
POWER ON:
Demand for Heat:
1. The low operator switch closes, energizing pump
delay timer TD4 and the water pump(s).
2. Water fl ow through the unit closes the water fl ow
switch contacts energizing blower delay timer TD3.
3. The system checks all primary limit(s) and other
inter-locks before starting pre-purge. The unit will not
start if any switch is open.
Prepurge:
1. Blower delay timer TD3 energizes the low speed
windings of the blower(s).
2. Once sufficient air pressure in the combustion
chamber is sensed the pressure switch closes
allowing the blower delay timer TD1 to start a 10
second pre-purge.
Ignition Trial:
1. Blower delay timer TD1 times out and the fl ame
sense module, FSM, is energized.
2. The FSM star ts the 10-second ignition trial,
energizing relay R7, the pilot solenoid valve and the
spark generator.
3. The pilot valve and spark generator are energized
for the 10-second ignition trial. When the pilot fl ame
is sensed, the FSM sends 24VAC to its MV terminal
energizing the safety and low fi re-side of the main
solenoid valves and relay R8, de-energizing R7 and
the spark generator.
4. If the pilot fl ame isn’t sensed, the FSM de-energizes
the PV terminal and waits 5 minutes before initiating
the second ignition trial. The blower(s), pump(s) and
optional power venter will remain on during this time.
5. On CSD-1 equipped units the blower(s) and optional
power venter will shut down and the boiler/water
heater will lock if the second ignition trial fails. The
unit must then be manually reset by depressing the
reset button on the left jacket panel.
6. On non-CSD-1 equipped units the FSM will wait 10
minutes after the second unsuccessful ignition
attempt then begin the ignition process described
in step 3 above. The FSM will continue to cycle the
unit through steps 3, 4 and 6 until the unit lights or
the demand for heat is removed.
Main Burner
Once the pilot is proven, the FSM sends 24VAC to its
MV terminal energizing the safety and low-fi re side of
the main solenoid valves.
Normal Operation
• Staging is controlled by the return water aquastat.
Relays R2 and R2R are energized by the return water
aquastat when more heat input is required. The
hi-speed windings of the blower(s) are energized.
• Relay R9 is energized when the hi-fi re pressure switch
senses adequate air pressure to sustain hi-fire
combustion. R9 energizes the hi-fi re side of the main
solenoid valve.
• Stage 1 will operate fi rst and last.
NOTE: For a change from stage 1 to 2, a 30 second
time delay is provided in the pressure switch
switching circuit. The time delay TD6 provides a
hold state that allows the blower to reach full speed
and close the high fi re pressure switch before it is
energized to confi rm proper air fl ow.
