SERVICING
28
WARNING
H
I
GH
V
OLTAG
E
D
IS
CONN
E
CT
ALL
PO
WER
B
E
FO
RE
SERVI
C
I
NG O
R
I
N
S
TALL
I
NG TH
IS
U
N
I
T.
M
U
LT
I
PL
E
PO
WER
S
O
UR
C
ES
M
AY
B
E
P
RESE
NT.
F
A
I
L
URE
TO DO
S
O
M
AY CA
USE
P
R
OP
ER
TY
DA
M
AG
E
, P
ERS
ONAL
I
N
JUR
Y O
R
D
E
ATH.
RED
RESET
BUTTON
COLOR
IDENTIFYING
Testing Auxiliary Limit Control
WARNING
T
O A
V
O
I
D PO
SSI
BL
E
F
IRE
, ONLY
RESE
T TH
E
A
UXI
L
I
A
R
Y L
IMI
T CONT
R
OL
ONC
E
.
I
F
I
T
S
HO
U
LD OP
E
N A
SE
COND T
IME
, A
QU
AL
I
F
IE
D
SERVI
C
ER
MUS
T D
E
T
ERMI
N
E
W
HY TH
E
A
UXI
L
I
A
R
Y L
IMI
T OP
E
N
E
D B
E
FO
RE
RESE
TT
I
NG AGA
I
N.
INDUCED DRAFT BLOWER MOTOR
WARNING
H
I
GH
V
OLTAG
E
D
IS
CONN
E
CT
ALL
PO
WER
B
E
FO
RE
SERVI
C
I
NG O
R
I
N
S
TALL
I
NG TH
IS
U
N
I
T.
M
U
LT
I
PL
E
PO
WER
S
O
UR
C
ES
M
AY
B
E
P
RESE
NT.
F
A
I
L
URE
TO DO
S
O
M
AY CA
USE
P
R
OP
ER
TY
DA
M
AG
E
, P
ERS
ONAL
I
N
JUR
Y O
R
D
E
ATH.
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
to a three phase supply to operate the draft inducer at the
desired speed. The windings of the induced draft motor will
have equal resi/- 5%. Normal resistance readings
at room temperature will range from 14-17 ohms. The volt-
age 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 colored ground wire is also present.
CHECKING GAS VALVE (Redundant)
A 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.
WARNING
D
IS
CONN
E
CT
ALL
PO
WER
B
E
FO
RE
SERVI
C
I
NG
Single stage gas valves should be tested on the furnance with
24 VAC connected to the gas valve and manometers reading
supply line and manifold pressures.
WARNING
D
IS
CONN
E
CT
ALL
G
A
S
AND
E
L
E
CT
RI
CAL
P
O
WER
S
U
PPLY.
Orifices should be treated with care in order to prevent
damage. They should be removed and installed with a box-
end wrench in order to prevent distortion. In no instance
should an orifice be peened over and redrilled. This will
change the angle or deflection of the vacuum effect or
entraining of primary air, which will make it difficult to adjust
the flame properly. This same problem can occur if an orifice
spud of a different length is substituted.
WARNING
D
IS
CONN
E
CT
ALL
G
A
S
AND
E
L
E
CT
RI
CAL
P
O
WER
S
U
PPLY.
CHECKING GAS PRESSURE
Gas Supply Pressure Measurement
T
O P
REVE
NT
U
N
RE
L
I
ABL
E
OP
ER
AT
I
ON O
R
EQUI
P
ME
NT DA
M
AG
E
, TH
E
I
NL
E
T GA
S
SU
PPLY P
RESSURE
MUS
T B
E
A
S
S
P
E
C
I
F
IE
D ON TH
E
U
N
I
T
R
AT
I
NG PLAT
E
WI
TH ALL OTH
ER
HO
USE
HOLD GA
S
F
IRE
D APPL
I
ANC
ES
OP
ER
AT
I
NG.
CAUTION
Gas inlet and manifold pressures should be checked and
adjusted in accordance to the type of fuel being consumed.
