Servicing - Goodman GMEC96 Service Instructions Manual

SERVICING

As more and more electronic's are introduced to the Heat-
ing Trade, Polarization of incoming power and phasing of
primary to secondary voltage on transformers becomes
more important.
Polarization has been apparent in the Appliance industry
since the introduction of the three prong plug, however, the
Heating Industry does not use a plug for incoming power,
but is hard wired.
Some of the electronic boards being used today, with flame
rectification, will not function properly and/or at all without
polarization of incoming power. Some also require phasing
between the primary and secondary sides of step-down
transformers.
CHECKING FOR PHASING - PRIMARY TO SECONDARY OF UNMARKED TRANSFORMERS*
METER READS
24 VOLTS
.
VOLT / OHM
METER
If meter reads approximately 96 volts - the primary to secondary are in phase - if reads approximately 144 volts out of
phase - reverse low voltage wires.
*NOTE: For flame rectification the common side of the secondary voltage (24 V) is cabinet grounded. If you were to bench
test a transformer the primary neutral and secondary common must be connected together for testing purposes.
C
24 V
R
PHASING SYMBOL
. . .
.
.
LINE VOLTAGE
TRANSFORMER
(NEUTRAL)
C
R
LINE VOLTAGE
L1 (HOT)
VOLT / OHM
METER
NEUTRAL
120 V
L1
METER READS
120 VOLTS
VOLT / OHM
METER
THIS IS L1 OR THE
HOT POWER LEG
These then should be wired to the furnace accordingly.
C
METER READS
120 VOLTS
R
VOLT / OHM
METER
READS 96 VOLTS - IN PHASE
C
R
READS 144 VOLTS - OUT OF PHASE
Some transformers will display phasing symbols as shown
in the illustration to the left to assist in determining proper
transformer phasing.
Checking for polarization and phasing should become a
habit in servicing. Let's start now.
NOTE: Newer integrated ignition controls have a diagnos-
tic flash code for reversed polarity (Refer to Troubleshoot-
ing-Diagnostic Chart for LED Codes).
INCOMING POWER
METER READS
0 VOLTS
VOLT / OHM
METER
THIS IS THE COMMON
OR NEUTRAL LEG
N
L1
VOLT / OHM
METER
N
L1
VOLT / OHM
METER
49