Daikin DCG Series Service Instructions Manual page 70

SERVICING
5. The control monitors the safety circuit inputs, flame, and
thermostat during operation.
6. When the thermostat is satisfied, the gas valve is de-
energized and the induced draft blower remains on for a
29 second post purge. The indoor blower remains on for
the selected heat blower off delay (90, 120, or 150
seconds). Indoor blower off timing begins when thermo-
stat call for heat ends.
Testing Direct Spark Ignition (DSI) systems
Thermostat calling for heat (15 second prepurge time and 7
second trial for ignition).
1. Check for 230 VAC from L1 terminal of control module to
L2. No voltage - check wire connections, continuity, etc.
2. Check for 24 VAC at "R" to "C" thermostat terminals.
a. No voltage - check 3 amp automotive type fuse on
control board. A blown fuse would indicate a short
in the 24 VAC circuit (thermostat or limit circuit).
b. Voltage Present - check limit, auxiliary limit and
rollout (S-300, S-301 and S-302). If limit, auxiliary
limit and rollout are closed, then check for 24 VAC
at the gas valve terminals.
No 24 VAC at gas valve - replace Control board.
TROUBLESHOOTING
I C E
GNITION ONTROL RROR
The following presents probable causes of questionable unit
operation. Refer to Diagnostic Indicator Chart for an
interpretation of the signal and to this section for an explana-
tion.
Remove the control box access panel and note the number
of diagnostic LED flashes. Refer to Diagnostic Indicator
Chart for an interpretation of the signal and to this section for
an explanation.
Internal Control Failure
If the integrated ignition control in this unit encounters an
internal fault, it will go into a "hard" lockout and turn off the
diagnostic LED. If diagnostic LED indicates an internal fault,
check power supply to unit for proper voltage, check all fuses,
circuit breakers and wiring. Disconnect electric power for five
seconds. If LED remains off after restoring power, replace
control.
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BNORMAL PERATION
External Lockout (1 FLASH CODE)
An external lockout occurs if the integrated ignition control
determines that a measurable combustion cannot be estab-
lished within three (3) consecutive ignition attempts. If flame
is not established within the seven (7) second trial for ignition,
the gas valve is deenergized, 15 second inter-purge cycle is
completed, and ignition is reattempted. The control will
repeat this routine three times if a measurable combustion
is not established. The control will then shut off the induced
draft blower and go into a lockout state.
If flame is established but lost, the control will energize the
circulator blower at the heat speed and then begin a new
ignition sequence. If flame is established then lost on
subsequent attempts, the control will recycle for four (4)
consecutive ignition attempts (five attempts total) before
locking out.
The diagnostic fault code is 1 flash for a lockout due to failed
ignition attempts or flame dropouts. The integrated control
will automatically reset after one hour, or it can be reset by
removing the thermostat signal or disconnecting the electri-
cal power supply for over five seconds. If the diagnostic LED
indicates an external lockout, perform the following checks:
• Check the supply and manifold pressures
• Check the gas orifices for debris
• Check gas valve for proper operation
• Check secondary limit
A dirty filter, excessive duct static, insufficient air
flow, a faulty limit, or a failed circulator blower can
cause this limit to open. Check filters, total external
duct static, circulator blower motor, blower motor
speed tap (see wiring diagram), and limit. An
interruption in electrical power during a heating
cycle may also cause the auxiliary limit to open.
The automatic reset secondary limit is located on
top of the circulator blower assembly.
• Check rollout limit
If the burner flames are not properly drawn into the
heat exchanger, the flame rollout protection device
will open. Possible causes are restricted or blocked
flue passages, blocked or cracked heat exchanger,
a failed induced draft blower, or insufficient combus-
tion air. The rollout protection device is a manual
reset limit located on the burner bracket. The cause
of the flame rollout must be determined and cor-
rected before resetting the limit.
• Check flame sensor
A drop in flame signal can be caused by nearly
invisible coating on the sensor. Remove the sensor
and carefully clean with steel wool.
• Check wiring
Check wiring for opens/shorts and miswiring.
C
EATING ODES