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4. Once the system check and pre-purge cycles are
complete, the control will enter the ignition cycle.
The modulating valve and inducer will go to their "light
off" settings.
The DSI ignition module will be energized and the
spark ignitor will activate.
The redundant safety valve will open, allowing gas
flow.
The burners will ignite and the control will receive a
signal from the flame sensor.
The spark ignitor will remain active for the duration of
the ignition cycle, regardless of flame status.
5. If flame is not established during the ignition cycle, the
control will repeat the pre-purge and ignitions cycles
up to three times. After three failed ignition attempts,
the board will enter a 1 hour lockout.
6. Once flame has been established, the control will enter
a warm-up period to ensure flame stabilization and
reduce condensation in the heat exchanger.
7. After the warm-up period, the control will enter the run
cycle. During the run cycle, the burner firing rate and
draft inducer pressure are determined based on the
heat demand received by the control via a 0-10V analog
signal.
Note: If the control is paired with a split manifold, steps 1
through 6 pertain to the primary burners. Once the
control exits the warm-up period and the firing rate
is dictated by the rooftop control, the control will
ignite the secondary burners and modulate the
primary burners based on the demand for heat.
8. The run cycle will continue until any of the following
conditions are met.
a. The call for heat is terminated.
b. Any of the safety devices (high limit, air pressure,
rollout, etc.) are triggered.
c. The control reaches it's maximum run time of 6
hours. If this condition is reached, the control will
terminate the run cycle, continue through the
proper sequence of operations, and then
immediately enter the system check and pre-purge
cycles to prepare for re-ignition, assuming
conditions A and B haven't been met.
9. Once the run cycle has terminated, the redundant
safety valve will close, the modulating valve will return
to its set position, and the draft inducer will ramp up to
its "light-off" setting for a 45 second post-purge cycle.
10. After the conclusion of the post-purge, the control will
enter the "OFF" state. All system outputs are
de-energized but all safety devices are still monitored.
11. Operation will continue in high-fire mode until the
signal from the building management controller drops
to below 4.7 VDC. At this point the gas heat control
module de-energizes the second stage gas valve and
the combustion blower switches to low speed.
CLCH-SVX014B-EN
Start-Up — Indirect Gas-Fired Heating
12. When the building thermostat is satisfied and the
demand for heat ends, the gas valve is de-energized
immediately the combustion blower is energized on
high speed for 30-second post-purge period.
Normal Shutdown
The air-handling unit fan should run for a minimum of
three to ten minutes after heater shutdown to cool the heat
exchanger.
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