Safety Circuit Voltage Trace - Bradford White PDX Series Service Manual

PDX Series
Safety Circuit Voltage
Trace
NOTE: This procedure assumes a cool tank.
Step 2. Remove three screws (Phillips Screw driver) from control
access cover on blower and remove cover (see photo 24).
Position gas control switch to the "ON"
position and adjust thermostat dial to call
for heat, Is there 10 to 13 VAC between red
wire leading to blower temperature switch
and green ground wire?
Blower must be running during this
voltage check.
(see photo 25)
Y
Is there 10 to 13 VAC between yellow wire
leading from pressure switch and green
ground wire?
(see photo 25)
Y
Do you hear or can you see
the igniter sparking?
Y
Safety circuit
voltage is OK.
If burner does not light,
observe LED flash code on
gas valve and refer to
troubleshooting section on
page 13
making voltage checks to avoid personal injury.
Is LED on gas valve flashing the
N
"heartbeat" code (alternating
bright/dim)
N
Verify 120VAC to gas
control (see page 30)
N
Correct igniter/
sensor problem.
Check igniter/sensor
N
(see page 17)
is igniter/sensor OK?
25
PDX SERVICE PROCEDURE VIII

Safety Circuit Voltage Trace

WARNING
120 volt potential exposure. Use caution
No voltage from gas control,
Y
call for technical support.
Is there continuity
through blower
temperature switch?
(see page 21)
N
Determine cause of blower
temperature switch activation
and correct.
Faulty cord set or
Y
gas control.
24
Check for loose or
Y
broken wire connection
at switch terminals
Green ground wire
Red wire leading to
blower temp. switch
Yellow wire
leading from
pressure switch
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