Daikin DM80SE, Service Instructions Manual

Page: 27 / 34

SERVICING
27
CHECKING AUXILIARY LIMIT CONTROL
BLOWER HOUSING
AUXILIARY LIMIT CONTROL
Auxiliary Limit Control Location
WARNING
HIGH VOLTAGE
D
ISCONNECT
ALL
POWER BEFORE SERVICING OR
INSTALLING THIS UNIT.
M
ULTIPLE POWER SOURCES MAY
BE PRESENT.
F
AILURE TO DO SO MAY CAUSE PROPERTY
DAMAGE, PERSONAL INJURY OR DEATH.
VOLT / OHM
METER
RED
RESET
BUTTON
COLOR
IDENTIFYING
TAB
Testing Auxiliary Limit Control
WARNING
T
O AVOID POSSIBLE FIRE, ONLY RESET THE AUXILIARY LIMIT CONTROL
ONCE.
I
F IT SHOULD OPEN A SECOND TIME, A QUALIFIED SERVICER
MUST DETERMINE WHY THE AUXILIARY LIMIT OPENED BEFORE
RESETTING AGAIN.
INDUCED DRAFT BLOWER MOTOR
DM80SE*U
WARNING
HIGH VOLTAGE
D
ISCONNECT
ALL
POWER BEFORE SERVICING OR
INSTALLING THIS UNIT.
M
ULTIPLE POWER SOURCES MAY
BE PRESENT.
F
AILURE TO DO SO MAY CAUSE PROPERTY
DAMAGE, PERSONAL INJURY OR DEATH.
1. Remove burner compartment door to gain access to
the induced draft blower motor.
2. Disconnect the motor wire leads from its connection
point at the induced draft motor.
3. Using a ohmmeter, test for continuity between each of
the motor leads.
4. 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.
5. If the windings have a continuity reading, reconnect
wires. Turn power on to the furnace and turn the
thermostat on in the heating mode. Check voltage for
115V at the induced draft motor terminals during the
trial for ignition. If you have 115V and the motor does
not run, replace the induced draft motor.
6. After completing check and/or replacement of induced
draft motor, reinstall burner compartment door.
7. Turn on electrical power and verify proper unit opera -
tion.
DM80SN*U
The induced draft assembly uses a three phase motor to
draw flue gases through the heat exchanger. The inducer
uses ball bearings and is permanently lubricated. This motor
is driven at varying speeds by the VFD (variable frequency
drive) section of the IFC. The IFC takes typical single phase
power supplied to the furnace and converts it into a three
phase supply to operate the draft inducer at the desired
speed. The wingings of the induced draft motor will have
equal resistance +/- 5%. Normal resistance readings at
room temperature will range from 14-17 ohms. The voltage
supplied by the IFC to drive the induced draft blower will vary
from 15-110 volts A/C between any two windings. This would
be read between any two of the three power wires between
the IFC and the induced draft blower. This voltage to the IBD
will vary between furnace models and is dependent on what
percentage of maximum fire is being called for. The power
wires are colored red, white and black. A green ground wire
is also present.