SERVICING
27
Some of the electronic boards being used today, with ame
rectication, 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.
120.00
0.00
GND
GND
THIS IS L1 OR THE
HOT POWER LEG
THIS IS THE COMMON
OR NEUTRAL LEG
INCOMING POWER
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
.
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.
C
R
GND
L1
These then should be wired to the furnace accordingly.
Some transformers will display phasing symbols as shown
in the illustration to the left to assist in determining proper
transformer phasing.
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