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19. SEQUENCE OF OPERATION FOR FENWAL DSI CONTROL
OPERATION
Upon applying power (24VAC) to 24V terminal, the control will reset, perform a self check rou-
tine, initiate full time flame sensing, flash the diagnostic LED for up to four seconds, and enter
the thermostat scan state.
HEAT MODE
Upon call for heat from the thermostat, 24 volts is supplied to TH/W, the gas valve is energized
and spark commences at both burners for the trial for ignition period (up to 24 seconds total).
When flame is detected during trial for ignition, spark is shut off immediately and the gas valve
remains energized. The thermostat and burner flame are constantly monitored to assure the
system continues to operate properly. When the thermostat is satisfied and the demand for
heat ends, the main valve is de-energized immediately.
MULTI-TRY IGNITION CONTROL
Should either burner fail to light, or flame is not
detected during the first trial for ignition period, the
gas valve is de-energized and the control goes
through an inter-purge delay. The control system
will follow this sequence three (3) times before
lock out occurs.
Recovery from lockout requires a manual reset by
either resetting the thermostat or removing 24
volts for a period of 5 seconds. Allow 5 minute
shutdown period before relighting the burner.
FLAME FAILURE-RE-IGNITION
If the established flame signal is lost from either burner while the burners are operating, the
control will respond within 0.8 seconds. After a 5 second inter-purge period, the high voltage
spark will be energized for a trial ignition period (remaining time after previous trials - up to 24
seconds total) in an attempt to relight the burners. If either burner does not light the control will
de-energize the gas valve. The Multi Try Ignition Control will make two attempts to relight the
burners. If either burner does not relight the control will go into lockout as noted above in
"Failure to light". When flame is re-established, normal operation resumes.
FLAME FAULT
If at any time the main valve fails to close completely and maintain a flame, the full time flame
sensing circuit will detect it and flash an error code of 2.
FLAME CONDITION - FLAME CURRENT CHECK
Flame current is the current which passes through the flame from the sensor to ground. The
minimum flame current necessary to keep the system from lockout is .7 microamps. To meas-
ure flame current, connect an analog DC micrometer to the FC – FC+ terminals. Meter should
read .7 µA or higher. If meter reads below "0" on scale, meter leads are reversed. Disconnect
power and reconnect meter leads for proper polarity.
SP-MECX-EX-5A
ECO-X 36-52 / IL-X 150-200 Manual
RD: MAY 2009
RL: 05A - BA
MODE
Internal Control
Failure
Start up
Flame with no call
for heat
Ignition Lockout
Valve relay lockout
28
LED INDICATION
Steady On
1 flash
2 flashes
3 flashes
4 flashes
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