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Polarity Check
Proper line voltage polarity, or
phasing, is a must for this furnace to
operate at all. Use a volt meter to
make this check.
1. With the blower compartment
door off, manually hold the push
button door switch in.
2.
Use a voltmeter to measure the
voltage from terminal L 1 to any
bare metal ground on the
furnace.
3. The voltage should be a nominal
115 volts.
4.
Use a voltmeter to measure the
voltage from any Neutral
terminal to the bare metal
ground on the furnace.
5.
The voltage should be a very
low amount, preferably zero
(0) volts.
6. If the voltage from L 1 to ground
is approximately zero (0) volts
and the voltage from a Neutral
to ground is a nominal 115 volts,
the polarity is reversed.
7. To correct the problem either
reverse the hot and neutral
wires to the furnace or have a
licensed electrician check the
building wiring.
Control Voltage Check
1. With the blower compartment
door off, manually hold the push
button door switch in.
2. Call for heat at the thermostat.
3. With the unit operating, use a
voltmeter to measure the
voltage from control voltage
terminal
"W' to terminal "C" on
the furnace control board.
4. The voltage should be a nominal
24 volts.
This test should be made with the
unit in full operation.
FIGURE77
POLARITY CHECK
FIGURE78
LOW VOLTAGE CHECK
65
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