21
120 volt potential exposure.
Use caution making voltage
checks to avoid personal injury.
WARNING
Removing screw from
inlet gas pressure tap will
immediately allow gas to
flow from pressure tap.
WARNING
Service Procedure II:
Combustion System Testing and Replacement
Observe burner operation through the sight glass located on the combustion insert mounting flange. Normal burner
operation should ignite smoothly, without evidence of coughing or huffing upon ignition. The burner flame should be a blue
flame near the burner surface in a uniform flame pattern. Occasional yellow or white streaks are normal.
Note: On this high input model that uses metal fiber mesh burner a red glow from the burner surface is normal.
N
Verify minimum gas supply piping requirements of: Minimum ¾” NPT
(Schedule 40 black iron pipe recommended.)
Reconfigure gas supply piping
With manometer, check inlet gas
pressure. Is it stable between 7” &
14” W.C. static (heater not
running)? (See illustrations at right.)
Is gas supply pressure
regulator adjustable to
maintain proper and
stable setting?
Inadequately
sized regulator.
Adjust gas
supply regulator.
Does inlet gas
pressure drop more
than 2” W.C. during
burner ignition?”
Can sparking be
seen/heard at the
spark rod to burner?
Remove high voltage wire
connected at the spark rod and
hold approximately ¼” from
metal ground with insulated
pliers during the ignition cycle (3
second spark trial period). Is
there spark to ground?
Check resistance of high
voltage cable. Resistance
should be 0-1 Ohm. If
resistance is high, replace
spark cable. If spark cable is
good, replace control board.
Check continuity of
spark rod. Is
reading 0-1 Ohm?
Replace spark rod (see
“Spark Rod Gap Inspection
and Replacement”).
Does main burner light?
Check spark gap to
burner (see “Spark Rod
Gap Inspection”).
Proceed to next page.
N
N
N
N
N
N
N
Y
Y
Y
Y
Y
Y
Y
Y
Volt meter set
of OHM setting
CHECK SPARK
ROD RESISTANCE
Meter probe
Spark
rod
Meter probe
gas
valve/venturi
Volt meter set
to OHM setting
Spark
rod
Inlet
Pressure
Tap
21
