POLARIZATION AND PHASING
13
As more and more electronics are introduced to the Heating
Trade, Polarization of incoming power and phasing of pri
-
mary 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 phas
-
ing between the primary and secondary sides of step-down
transformers.
THIS IS L1 OR THE
HOT POWER LEG
INCOMING POWER
THIS IS THE COMMON
OR NEUTRAL LEG
METER READS
120 VOLTS
METER READS
0 VOLTS
GN
D
GN
D
VOLT / OHM
METER
VOLT / OHM
METER
These then should be wired to the furnace accordingly.
CHECKING FOR PHASING - PRIMARY TO SECONDARY OF UNMARKED TRANSFORMERS*
.
.
.
.
.
.
VOLT / OHM
METER
G
ND
P
R
I
M
A
R
Y
SE
C
O
N
D
A
R
Y
TRANSFORMER
R
C
METER READS
24 VOLTS
LINE VOLTAGE
(NEUTRAL)
LINE VOLTAGE
L1 (HOT)
VOLT / OHM
METER
METER READS
120 VOLTS
VOLT / OHM
METER
C
R
G
N
D
N
L1
VOLT / OHM
METER
READS 96 VOLTS - IN PHASE
C
R
G
N
D
N
L1
VOLT / OHM
METER
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.
*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 connect
-
ed together for testing purposes.
C
R
G
N
D
NEUTRAL
L1
PHASING SYMBOL
24 V
120 V
WARNING
HIGH VOLTAGE
Disconnect ALL power before servicing or in
-
stalling this unit. Multiple power sources may
be present. Failure to do so may cause proper
-
ty damage, personal injury or death.