Daikin DBG Series, Service Instructions Manual

Page: 18 / 108

SYSTEM OPERATION
18
Bearing Check
Prior to energizing any fans, check and make sure that all
setscrews are tight so that bearings are properly secured to
shafts.
GAS SYSTEM
Flame
Sensor
Ignitor
NATURAL PROPANE (LP)
350,000 7 50,000 #30 #48
400,000 8 50,000 #30 #48
GAS ORIFICES
MAXIMUM
INPUT
(BTUH)
NUMBER
of
BURNERS
MAXIMUM
BTUH/BURNER
HEAT EXCHANGER AND BURNER ORIFICE
SPECIFICATIONS
NOTE: Gas appliances located more than 2000 feet
above sea level must be derated 4% per 1000 feet of
total elevation and that variance in gas heating value and
specific gravity require change in manifold pressure to
obtain rating, it is mandatory that the input be adjusted
at the installation site. All installations should be made as
outlined in the latest edition of the National Fuel Gas Code
ANSI Z223.1, section “Procedures To Be Followed To
Place An Appliance in Operation”. Refer also to the “User’s
Information Manual” supplied with the unit for additional
information on the gas furnace.
NORMAL SEQUENCE OF OPERATION
NOTE : The ignition control board blower off delay is factory
set at 150 seconds. This factory setting can also be set to 120
or 135 seconds by placing the jumper on the desired setting.
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
ignition, 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 be-
tween 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) mi-
cro-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 estab -
lished, 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.