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SERVICING
3. Blower – "Fan" Speed for 15 seconds
4. Spark Igniter for 17 seconds
5. Inducer – "Run" setting 15 seconds
6. Inducer – 2.0" w.c. for 60 seconds
7. Return to OFF mode
Once the Field Test Mode is initiated, all thermostat inputs
will be ignored until the field test sequence is completed.
If the SW1 button is held for more than 15 seconds, the
button press will be ignored, and the LED display will
return to its prior state.
Checking Integrated Igntion Control Board
NOTE: Failure to earth ground the unit, or a high
resistance connection in the ground may cause the
control to lockout due to failure to sense flame. The
ground wire must run from the unit ground to the
electrical panel ground.
To avoid personal injury or death due to electric
shock, wiring to the unit must be properly grounded.
Disconnect power before installing or servicing.
The ignition control is a combination electronic and
electromechanical device and is not field repairable.
The tests below must be completed within a given time
frame due to the operation of the ignition control.
1. Check for 230 volts from Line 1 to Line 2 at the ignition
control.
2. Check for 24 volts from W to C terminals on the
ignition control. If no voltage, check transformer,
room thermostat and wiring.
If you have 24 volts coming off the transformer, but
have approximately 13 volts between C and R, check
for blown fuse.
3. Check for 230 volts to the induced draft blower by
measuring voltage between Pins 4 & 5 on 5-pin
connector.
4. If voltage is present in Steps 1 through 3 and the
induced draft blower is operating, check for spark
igniter and 24 volts to gas valve.
S-308 Checking For Delayed Ignition
Delayed ignition is a delay in lighting a combustible mixture
of gas and air which has accumulated in the combustion
chamber.
WARNING
When the mixture does ignite, it may explode and/or
rollout causing burning in the burner venturi.
If delayed ignition should occur, the following should be
checked:
1. Improper gas pressure - adjust to proper pressure.
Improper burner positioning - burners should be in
locating slots, level front to rear and left to right.
2. Carry over (lighter tube or cross lighter) obstructed -
clean.
3. Main burner orifice(s) deformed, or out of alignment
to burner - replace.
S-309 Checking For Flashback
Flashback will also cause burning in the burner venturi, but
is caused by the burning speed being greater than the gas-
air flow velocity coming from a burner port.
Flashback may occur at the moment of ignition, after a
burner heats up or when the burner turns off. The latter is
known as extinction pop.
Since the end results of flashback and delayed ignition
can be the same (burning in the burner venturi) a definite
attempt should be made to determine which has occurred.
If flashback should occur, check for the following:
1. Improper gas pressure - adjust to proper pressure.
Check burner for proper alignment and/or replace
burner.
2. Improper orifice size - check orifice for obstruction.
S-310 Checking Pressure Control
A pressure control device is used to measure negative
pressure at the induced draft blower motor inlet to detect
a partial or blocked flue.
Pressure Switch Operation
(DSI Direct Spark System)
The pressure switch is ignored unless there is a call for
heat. When the control receives a call for heat, the control
checks to see that the pressure switch is open. If the
control sees that the pressure switch is closed before the
induced draft blower is energized, the LED will flash a code
of "2" (to indicate the pressure switch is stuck closed) and
the inducer will remain off until the pressure switch opens.
If the pressure switch opens before the ignition period, the
induced draft blower will remain on and the control will
stay in pre-purge until the pressure switch is closed for an
entire 15 second pre-purge period. The LED will flash a
code of "3" to indicate open pressure switch.
31
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