Testing Inducer Motor; Testing Gas Valve - Daikin DBG Series Service Instructions Manual

SERVICING
If a limit switch opens, the indoor blower is energized on heat
speed and the induced draft blower is energized. The LED on
the control flashes "4" to indicate an open limit switch. The
blower and inducer remain on while the limit switch is open.
The gas valve is de-energized. Power to the thermostat "R"
is removed while the limit switch is open.
When the limit switch re-closes, the induced draft motor runs
through its post purge and the indoor blower goes through
the heat off delay.
If a call for heat exists when the limit switch re-closes, the
control goes through a pre-purge period and then makes an
ignition attempt. The indoor blower remains on (for the delay
off time) during the re-ignition attempt.
1. If no voltage is measured on either side of control
it indicates ignition control or wiring to control problem.
2. If voltage is measured on one side of the control
and not the other, it indicates the control is open.
3. If voltage is measured on both sides of the control the wiring
to gas valve or valve is at fault.
Servicing procedure with furnace not firing.
1. Confirm that the outer door was in place and all screws
tightened. (No leaks under the door.)
2. Check to see if any damage was done to the furnace
especially the wiring.
3. Confirm that heat exchanger is not obstructed by feeling
for discharge air from the flue hood when the combustion
blower is running but the unit is not firing.
If the above steps do not suggest the reason the control has
tripped the furnace should be fired.
1. Remove the heating compartment door.
2. Turn of the power or open the thermostat circuit.
3. Reset the rollout control.
4. Turn power on and put the unit into a call for heating.
CAUTION
Flame rollout could occur. Keep face and hands a
safe distance from burner area.
5. Look under the heat shield as the unit is running. Flames
should be drawn into firing tubes.
a. If only one burners flame is not drawn into the tube,
that tube is restricted.
b. If, without the air circulation blower running, all flames
are not drawn into the tubes either the collector box,
combustion blower, or flue outlet is obstructed. If
the combustion blower or flue outlet is obstructed,
the pressure switch should have opened preventing
the unit from firing, also inspect the unit pressure
switch and wiring.
c. If the burner flame is not drawn into the tube only
when the air circulation blower is running, then a
cracked heat exchanger tube is present.
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S-303 TESTING INDUCER MOTOR
HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing this unit. Multiple power
sources may be present. Failure to do so
may cause property damage, personal injury
or death.
1. Disconnect the motor wire leads from its connection point
at integrated ignition control module.
2. Using and ohmmeter, test for continuity between each of
the motor leads.
3. Touch one probe of the ohmmeter to the motor frame
(ground) and the other probe in turn to each lead.
If the windings do not test continuous or a reading is obtained
to ground, replace the motor.
4. After completing check and/or replacement of induced
draft blower motor.
5. Turn on electrical power and verify proper unit operation.
S-304 TESTING GAS VALVE
Direct Spark Ignition (DSI) Systems
TWO STAGE MODELS ONLY: A two-stage combination
redundant operator type gas valve which provides all manual
and automatic control functions required for gas fired heating
equipment is used.
The valve provides control of main burner gas flow, pressure
regulation, and 100 percent safety shut-off.
HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing this unit. Multiple power
sources may be present. Failure to do so
may cause property damage, personal injury
or death.
1. Ensure gas valve and main gas supply are on.
2. Using a voltmeter, check from C and M on gas valve for
24 volts to gas valve.
3. If 24 volts are present and no gas flows through the valve,
replace valve.