A.O. Smith DB/DW-720-1810 User Manual page 37

Attach wires firmly.
Replace gas valve.
Turn on power supply.
Securely connect cable
and/or ground wire.
Replace cable and/or
ground wire.
Carefully bend down-
wards top of ground
strap to achieve
1/8" spark gap.
Replace pilot
burner.
Replace ignition
module.
SPARK AT PILOT BURNER BUT PILOT WILL NOT LIGHT
Ensure all manual shutoff valves are fully open; All filters are clean;
All gas connections are gas tight; Pilot tubing is not damaged,
obstructed or kinked; and pilot orifice is unclogged. Check for
air in gas line, purge (bleed) line if necessary.
NO
Are the wires securely attached to the pilot operator on the gas
control and to the PV & MV/PV terminals on the ignition module?
Install a pressure gauge in the pilot tubing line between the gas
NO control and the pilot burner assembly. Ensure that the pilot
adjustment screw (under cap) is adjusted to a position that will
permit gas to flow.
Is pilot gas flowing during ignition attempt?
NO Is ignition cable firmly plugged into pilot assembly and module?
Is ground wire firmly attached to pilot assembly and GND
terminal on module?
NO Are ignition cable and ground wire in good condition (not brittle,
burnt, or cracked)?
Ensure ground strap is the closest metal to the igniter/sensor
rod (electrode) to prevent the spark from shorting out
NO to other metal parts (pilot screen, pilot shield, etc.).
Ignition cable must not touch metal surfaces or current carrying
wires.
Is there a 1/8" gap between ground strap and electrode?
NO
Is the ceramic insulator surrounding the electrode in good
condition (not cracked or broken)?
NO
Is there excessive draft conditions that may cause pilot burner
ignition problems?
Correct draft problems in a manner that would ensure adequate
combustion and ventilation air and proper pilot burner performance.
37
YES
YES
Turn off power supply.
YES
YES
YES
YES