beautypg.com

Pdx series, Safety circuit voltage trace – Bradford White PDX-75S-70FB-3X User Manual

Page 31

background image

PDX SERVICE PROCEDURE VIII

Safety Circuit Voltage Trace

Safety Circuit Voltage
Trace

WARNING

120 volt potential exposure. Use caution

making voltage checks to avoid personal injury.

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)

Red wire leading to

blower temp. switch

Green ground wire

25

Yellow wire

leading from

pressure switch

Y

Is there 10 to 13 VAC between yellow wire

leading from pressure switch and green

ground wire?

(see photo 25)

Do you hear or can you see

the igniter sparking?

Y

Y

Is LED on gas valve flashing the

“heartbeat” code (alternating

bright/dim)

N

Safety circuit

voltage is OK.

No voltage from gas control,

call for technical support.

Y

NOTE: This procedure assumes a cool tank.

Verify 120VAC to gas

control (see page 30)

Is there continuity

through blower

temperature switch?

(see page 21)

Y

Check for loose or

broken wire connection

at switch terminals

N

N

Determine cause of blower

temperature switch activation

and correct.

Check igniter/sensor

(see page 17)

is igniter/sensor OK?

If burner does not light,

observe LED flash code on

gas valve and refer to

troubleshooting section on

page 13

N

N

Page 31

24

Step 2.

Remove three screws (Phillips Screw driver) from control
access cover on blower and remove cover (see photo 24).

Faulty cord set or

gas control.

Y

Correct igniter/

sensor problem.

PDX Series

31

31