Bradford White EF120T4003NA3 Service Manual page 26

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.
Removing screw from inlet gas pressure tap will
immediately allow gas to flow from the pressure tap.
Verify minimum gas supply
piping requirements of:
Minimum 1" NPT (schedule 40
black iron pipe recommended).
Y
With a manometer, check inlet gas
pressure. Does it match the
pressures listed on page 6?
Y
Does inlet gas
pressure drop more
than 2" W.C. during
burner ignition?
N
N
Can sparking be
seen/heard at the
spark rod and
ground?
Y
Does main burner light?
Y
Proceed to next page.
26
Service Procedure II:
WARNING
N
Reconfigure gas supply piping.
Adjust gas
supply regulator.
Y
Is gas supply pressure
N
regulator adjustable to
maintain proper and
stable setting?
Y
Remove high voltage wire
connected at the spark rod
and hold approximately
1/4" from metal ground
with insulated pliers during
the ignition cycle (3 second
spark trial period). Is there
spark to ground?
Y
Check continuity of
spark rod. Is it
Y
reading 0-1 ohm?
N
Check spark gap to
burner (see Spark Rod
Gap Inspection, pg 37).
Volt meter set
to OHM setting
CHECKING SPARK
ROD RESISTANCE
120 volt potential exposure. Use caution making
voltage checks to avoid personal injury.
Inadequately
sized regulator.
N
Check resistance
of high voltage
cable. Resistance
should be 0-1
N
ohm. If resistance
is high, replace
spark cable. If
spark cable is
good, replace
control board.
Replace spark rod
N
(see Spark Rod Gap
Inspection and
Replacement, pg 37).
26
WARNING
Inlet
Pressure
Tap
Nat. Gas Valve/Venturi
Meter
probe
Spark
rod
Meter probe