Daikin DCG Series, Installation And Maintenance Manual

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4. Relight all other appliances turned off in step 1. Be sure all
pilot burners are operating.
Main Burner Flame Check
Flames should be stable, soft and blue (dust may cause orange
tips but they must not be yellow) and extending directly outward
from the burner without curling, floating or lifting off.
Temperature Rise Check
Check the temperature rise through the unit by placing thermom-
eters in supply and return air registers as close to the unit as pos-
sible. Thermometers must not be able to sample temperature di-
rectly from the unit heat exchangers, or false readings could be
obtained.
1. All registers must be open; all duct dampers must be in
their final (fully or partially open) position and the unit
operated for 15 minutes on HIGH FIRE before taking
readings.
2. The temperature rise must be within the range specified
on the rating plate.
NOTE: Air temperature rise is the temperature difference between
supply and return air.
With a properly designed system, the proper amount of tempera-
ture rise will normally be obtained when the unit is operated at
rated input with the recommended blower speed.
If the correct amount of temperature rise is not obtained, it may
be necessary to change the blower speed. A higher blower speed
will lower the temperature rise. A slower blower speed will in-
crease the temperature rise.
NOTE: Blower speed MUST be set to give the correct air
temperature rise through the unit as marked on the rating plate.
NORMAL SEQUENCE OF OPERATION - HEATING
This unit has one (RS) Manual Reset Limit Control Switch. Check
the limit to make sure it has not tripped. The limit may arrive at
the job site tripped as a result of shipping shock.
If the ventor motor comes on, but the unit does not attempt igni-
tion, check if the ALS (Automatic Reset High Limit Control Switch)
requires resetting.
1. With electricity and gas turned on, the system switch in
the “HEAT” or “AUTO” position and the fan switch in the
“AUTO” position, the thermostat will close the circuit
between unit terminals R and W (R-W) when the
temperature falls below the thermostat setting.
2. D1 on IIC energizes relay IDMR.
3. Relay IDMR energizes the ventor motor IDM.
4. Operation of the vent motor closes the pressure switch PS
located in the burner compartment. the control then
initiates a 15-second pre-purge time delay. During this
period, the ventor motor will clear the combustion
chamber of any residual gas.
5. After the pre-purge period, the ignition control energizes
the Wl-C gas valve and simultaneously initiates a “three
(3)-try” spark ignition sequence.
6. When the burners are ignited, a minimum four (4) micro-
amp DC current will flow through the flame between the
sensor electrode and the grounded burner.
7. When the controller proves that the flame has been
established, it will keep the gas valve energized and
discontinue the ignition spark. First stage manifold
pressure will be approximately 2.0" w.c. for natural gas
and 7.0" w.c. for propane (LP).
8. If the control is unable to ignite the burners after its initial
attempt, it will initiate another purge and spark sequence.
A third purge and spark sequence will be initiated if the
second attempt is unsuccessful. If the third attempt is
unsuccessful, the controller will close the gas valve and
lock itself out. It may be reset by momentarily interrupting
power. This may be accomplished by briefly lowering the
room thermostat set-point below room temperature, or
by shutting off the main power to the unit. (See TP-105
for more details.)
9. Integrated ignition control will close its normally open
contacts after a delay of approximately 30 seconds. This
action energizes contactor BC and starts the supply fan
motor. Operation of the supply fan circulates air across
the heat exchanger and delivers heated air to the
conditioned space.
10. When the space temperature rises, the thermostat will
open R-W. Opening R-W will cause the gas valve to close,
and the furnace to shut down.
11. The furnace has three high temperature limit controls,
which can shut down the burner. They do not shut down
the ventor motor.
Unit Shutdown
1. Set the thermostat to lowest setting.
2. Turn off the electrical power supply to the unit.
3. Remove the heat exchanger door on the side of the unit
by removing screws.
4. Move the gas control valve switch to the OFF position. Do
not force.
5. Close manual gas shut off valve external to the unit.
6. Replace the heat exchanger door on the unit.
7. If cooling and/or air circulation will be desired, turn ON
the electrical power.
A
UTOMATIC
R
ESET
H
IGH
L
IMIT
C
ONTROL
(LS)
Located in the burner compartment on the heat exchanger, its sens-
ing element projects through the blower section bulkhead and
senses the temperature at the rear of the furnace. It will cycle the
furnace off if the temperature exceeds 100°F plus maximum rise.
A
UXILIARY
R
ESET
H
IGH
L
IMIT
C
ONTROL
(ALS)
Located in the blower compartment on the blower housing, it
senses air temperature within the blower compartment and pro-
tects the filters from excessive temperature. It will shut down the
furnace if it senses excessive temperatures.
Elevated temperatures at the control are normally caused by
blower failure. The reason for the opening should be determined
and repaired prior to resetting.