SERVICING
46
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.
polarization of incoming power. Some also require phasing
between the primary and secondary sides of step-down
transformers.
120.00
0.00
GND
GND
THIS IS L1 OR THE
HOT POWER LEG
THIS IS THE COMMON
OR NEUTRAL LEG
INCOMING POWER
These then should be wired to the furnace accordingly.
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.
test a transformer the primary neutral and secondary common must be connected together for testing purposes.
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.
Newer integrated ignition controls have a diagnostic
Troubleshooting-
Diagnostic Chart for LED Codes).
TRANSFORMER
.
SECONDARY
PRIMARY
.
GND
C
R
LINE VOLTAGE
L1 (HOT)
LINE VOLTAGE
(NEUTRAL)
METER READS
24 VOLTS
METER READS
120 VOLTS
.
GND
C
R
N
L1
.
GND
C
R
N
L1
READS 96 VOLTS - IN PHASE
READS 144 VOLTS - OUT OF PHASE
.
R
G
N
D
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