Daikin DCG Series Service Instructions Manual page 37

SYSTEM OPERATION
quence. 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 condi-
tioned 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 ventermotor.
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 R H L
UTOMATIC ESET IGH
Located in the burner compartment on the heat exchanger,
its sensing 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 H L C
UXILIARY IGH IMIT ONTROL
Located in the blower compartment on the blower housing, it
senses air temperature within the blower compartment and
protects 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 deter-
mined and repaired prior to resetting.
M R F R
ANUAL ESET LAME OLLOUT
Located in the burner compartment at the top of the burner
assembly, it senses high temperature that could occur if the
C (LS)
IMIT ONTROL
(ALS)
C (RS)
ONTROL
heat exchanger tubes were plugged and the flame was rolling
out instead of entering the tubes. It has a manual push-button
reset that cannot be actuated until the limit control has
cooled.
The reason for elevated temperatures at the control should be
determined and repaired prior to resetting this manual reset
control.
T
O AVOID PROPERTY DAMAGE, PERSONAL INJURY OR DEATH DUE TO FIRE
OR EXPLOSION, A QUALIFIED SERVICER MUST INVESTIGATE THE REASON FOR
THE ROLLOUT PROTECTION DEVICE TO OPEN BEFORE MANUALLY RESETTING
THE ROLLOUT PROTECTION DEVICE.
NORMAL SEQUENCE OF OPERATION
C
OOLING
Begin with power turned off at all disconnects.
1. Turn thermostat system switch to "Cool," and fan switch
to "Auto" and turn temperature setting as high as it will go.
2. Inspect all registers and set them to the normal open
position.
3. Turn on the electrical supply at the disconnect.
4. Turn the fan switch to the "ON" position. The blower
should operate after a 7 second delay.
5. Turn the fan switch to "Auto" position. The blower should
stop after a 65 second delay.
6. Slowly lower the cooling temperature until first stage
COOL (LOW COOL) starts. The blower, both fans, and
first stage compressor should now be operating. Allow
the unit to run 10 minutes, make sure cool air is being
supplied by the unit.
7. Lower the cooling temperature further until second stage
COOL (HIGH COOL) starts. The blower, both fans, and
both compressors should now be operating. Allow the
unit to run 10 minutes, make sure cool air is being
supplied by the unit.
8. Turn the temperature setting to the highest position,
stopping the unit. The indoor blower will continue to run
for 65 seconds.
9. Turn the thermostat system switch to "OFF" and discon-
nect all power when servicing the unit.
WARNING
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