Checking Flame Rollout Control; Induced Draft Blower Motor; Checking Modulating Gas Valve; S-304A Checking Inductor Coil - Amana AMVM97 Service Instructions Manual

SERVICING
AUXILIARY LIMIT
CONTROL
BLOWER HOUSING
Auxiliary Limit Control Location
S-302 CHECKING FLAME ROLLOUT CONTROL
A temperature activated manual reset control is mounted
to the manifold assembly on modulating furnace, as shown
in the following illustration.
FLAME
ROLLOUT
SWITCHES
* * *
*
2
*
* *
Flame Rollout Switch Location
(90% Upflow Furnace Shown, Counterflow Similar)
HIGH VOLTAGE
D ALL
ISCONNECT POWER BEFORE SERVICING OR
CHANGING ANY ELECTRICAL WIRING.
F
SOURCES MAY BE PRESENT. AILURE TO DO SO MAY CAUSE
PROPERTY DAMAGE, PERSONAL INJURY OR DEATH.
1. Turn off all power sources
2. Remove the two wires from the roll out switch
3. Using an ohmmeter, check for a closed circuit across
the two roll out switch contacts (this will be the same
reading that you see by touching your two meter leads
together).
56
AUXILIARY LIMIT
CONTROL
WARNING
M
ULTIPLE POWER
S-303 INDUCED DRAFT BLOWER MOTOR
Induced Draft Blower (IDB)
All modulating furnace models use a three phase induced
draft blower 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 to a three phase supply to operate the
draft inducer at the desired speed. The windings 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 dependant on what
percentage of maximum fire is being called for. The power
wires are colored red, white and black. A green colored
ground wire is also present.
S-304 CHECKING MODULATING GAS VALVE
Gas ValveModulating furnaces use a 24 VAC pneumatically
operatedgas valve by Honeywell. The valve is energized
by the inte-grated furnace control on a call for heat, wired
in series through the front-cover pressure switch. The fir-
ing rate percentage is determined by the negative pres-
sure created by the operation of the draft inducer. The
gas valve is factory set and non-adjustable in the field. Do
not remove the seal covering the regulator screws or at-
tempt to adjust either of the regulator screws. Even though
the modulating gas valve is non-adjustable in the field,
gas industry procedure dictates that the installing / ser-
vicing technician should know that the appliance is oper-
ating as designed before leaving newly installed or ser-
viced equipment. The gas valve is equipped with 1/8 NPT
fittings to access both the inlet and manifold gas pres-
sures. To do a manifold gas pressure check, the furnace
can be operated in field test mode. This mode will quickly
bring the furnace up to high fire. To enter field test mode;
during a call for heat, press the fault recall button twice
within a five second period; when the dual seven segment
displays show Ft, press the fault recall button again to
enter field test mode.The furnace will stay in field test for
five minutes or until the call for heat is satisfied. Gas
valve orientation must be such that the switch is facing
out towards the front of the furnace.

S-304A CHECKING INDUCTOR COIL

Wired in series with ¾ and 1 HP ECM motors; the inductor
coil conditions the power supply to the motor, smoothing
out spikes and electrical noise. With voltage applied to
one side of the inductor coil, the output voltage to the
motor should be the same as incoming voltage.