34
TECHNICAL INFORMATION
“Troubleshooting Guide”
Nuisance Lockouts/Flame Sensing Problems – EHG Gas Burners
Wayne’s EHG series direct spark ignition (DSI) gas
burners prove flame through the process of flame
rectification. Flame rectification is achieved by placing a
small voltage on the flame sensing probe. When the probe
is surrounded by flame, the voltage on the probe “flows” to
ground through the flame, resulting in an electrical current.
This current is interpreted by the ignition control as the
presence of flame.
One of the most common problems with gas appliances
utilizing this type of electronic flame sensing system is the
“nuisance lockout”. Lockouts are not generally due to the
burner failing to ignite, but rather simply the failure of the
system to sense the establishment of the flame. Should
this situation exist for a period of time longer than the
ignition control’s state lockout timing, the control will shut
down or go into permanent lockout. The only way to get
the burner to recycle is to break, and then re-establish
power to the burner.
The following situations can lead to flame sensing
problems and can be checked without disassembling
the burner:
•
The burner is not properly grounded to “earth ground”
on line voltage.
•
The ignition control is not properly grounded to the
burner itself. Using an ohm meter, check the wire
attached to both parts for good contact and continuity.
•
The burner ignition control is polarity sensitive. The
polarity of the incoming line voltage may be reversed.
Verify that black and white wires are hot and neutral
respectively, and that they are connected to the
corresponding black and white wires on the burner.
The remaining checks and/or adjustments require
removal of the gas train, and burner head assembly:
•
The connections from the “SENSE” terminal of the
ignition control to the end of the flamerod may be
broken at some point. Check all quick connect
terminations and connections. Check the continuity
with an ohmmeter while flexing wires to assure no
hidden conductor breakage exists. If replaced, wiring
must be of equal or heavier gauge and equal or better
temperature rating.
•
The flamerod probe may be grounded out. Assure that
the flamerod probe is not touching the burner head.
The probe should be position in the center of the
clearance groove on the outer edge of the burner head
with approximately 1/16” (1.5875mm) clearance from
the head. The probe must not be positioned too far
away from the head as this may result in grounding
out of the probe against the inside surface of the air
tube.
•
The flamerod probe should be free of soot and
creosote. Deposits may insulate the probe, leading it
not to pass the electrical charge to the flame. The
probe can be cleaned with steel wool, emery paper or
fine sandpaper. NOTE: This is the leading cause of
nuisance lockouts in dual-fuel wood/gas fired
appliances.
•
The flamerod probe may be burned away. Check it
against dimensions on the ELECTRODE AND
FLAMEROD PROBE SETTINGS, figure 1.
•
The dimensional location of the flamerod probe may
be incorrect, or the probe may be bent out of shape.
Check it against dimensions on the ELECTRODE AND
FLAMEROD PROBE SETTINGS, figure 1, and adjust
if necessary.
•
The spark electrode gap may be incorrect, resulting in
no spark or an inadequate spark that will not ignite the
gas properly. Check the electrode gap against the
ELECTRODE AND FLAMEROD PROBE SETTINGS,
figure 1, and adjust if necessary.
•
The high tension lead conductor from the ignition
transformer to the tip of the spark electrode may be
broken, preventing the high voltage current from
getting to the electrode tip. Check all connections
thoroughly and/or check to continuity of the lead wire
assembly with an ohmmeter.
Once all of the items listed previously have been carefully
checked and corrected if necessary, reinsert the burner
head assembly into the burner. NOTE: be careful not to
bend the air proving switch sail arm (if so equipped) or
accidentally reposition with the flamerod probe or
electrode during reinstallation of the burner head train
assembly.
If, after all of the above listed items have been carefully
checked, the burner still fails to work, it is due one of or
more of the following problems:
1. Unit sparks and fires but will not stay lit. Ignition
control module is malfunctioning and must be
replaced.
2. Unit does not spark. Ignition transformer is bad
and must be replaced.