Daikin DRG0361DL00001S Service Instructions Manual page 40

SYSTEM OPERATION
NOx Screen Check
Verify that the alignment of the NOx screens is at 6
o' clock. In jurisdictions that do not require low NOx
emissions, NOx screens may be removed.
Temperature Rise Check
Check the temperature rise through the unit by placing
thermometers in supply and return air registers as close
to the unit as possible. Thermometers must not be
able to sample temperature directly 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 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
temperature 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 increase 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 venter motor comes on, but the unit does not
attempt ignition, check if the ALS (Auxiliary 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 venter motor contactor.
3. Venter motor contactor energizes the venter motor.
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4. Operation of the venter motor closes the pressure
switch PS located in the burner compartment. Unless
excessive temperatures or shipping shock have
opened high limit control ALS, power is fed to the
integrated ignition control, which then initiates a
15-second pre-purge time delay. During this period,
the venter fan 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 one (1)
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.
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.
9. Integrated ignition control will close its normally open
contacts after a delay of approximately 30 seconds.
This action energizes the blower motor contactor 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 venter motor.
Unit Shutdown
1. Set the room heating setpoint 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.
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 gas control valve switch and the electrical power.