Service Manual

68
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
Is gas supply pressure
regulator adjustable to
maintain proper and
stable setting?
Adjust gas
supply regulator.
Does inlet gas
pressure drop more
than 2” W.C. during
burner ignition?
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?
Replace spark rod (see Spark Rod Gap
Inspection and Replacement, pg 79).
Removing screw from inlet gas pressure tap will
immediately allow gas to flow from pressure tap.
WARNING
Verify minimum gas supply piping requirements of: Minimum ¾” NPT
(schedule 40 black iron pipe recommended.)
Reconfigure gas supply piping.
Inadequately
sized regulator.
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 spark gap to burner (see Spark Rod Gap Inspection, pg 79).
Proceed to next
page.
120 volt potential exposure. Use caution making
voltage checks to avoid personal injury.
WARNING
N
N
N
N
N
N
N
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Gas Valve/Venturi
CHECK SPARK ROD RESISTANCE
Volt meter set
of OHM setting
Meter probe
Spark rod
Meter probe
Inlet
Pressure
Tap
With manometer, check inlet gas
pressure. Is it stable between 7” &
14” W.C. (Nat) and 14” & 11” W.C.
(L.P.) static (heater not running)?
(see image).
Can sparking be
seen/heard at the
spark rod to burner?
Check continuity of spark
rod. Is reading 0-1 Ohm?
Does main burner light?
N
N
Y
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