Service Manual

27
27
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
Adjust gas
supply regulator.
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 38).
Removing screw from inlet gas pressure tap will
immediately allow gas to flow from pressure tap.
WARNING
Reconfigure gas supply piping.
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 38).
Proceed to next
page.
120 volt potential exposure. Use caution making
voltage checks to avoid personal injury.
WARNING
Is gas supply pressure
regulator adjustable to
maintain proper and
stable setting?
Does inlet gas
pressure drop more
than 2” W.C. during
burner ignition?
Verify minimum gas supply piping requirements of: Minimum ¾” NPT
(schedule 40 black iron pipe recommended.)
Inadequately
sized regulator.
N
N
N
N
N
Y
Y
Y
Y
Y
Y
Y
Gas Valve/Venturi
Volt meter set
of OHM setting
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).
CHECK SPARK ROD RESISTANCE
Can sparking be
seen/heard at the
spark rod to burner?
Meter probe
Spark rod
Meter probe
Inlet
Pressure
Tap
Check continuity of spark
rod. Is reading 0-1 Ohm?
Does main burner light?
N
N
Y