Midco International Inc.
9
8470 70
Service
Inspect the electrode wire insulation for cracks or worn areas, or any contact with the burner frame.
Dampness will facilitate electrical leakage to ground, which will cause ignition or fl ame signal failure.
Check that the electrode ends
are positioned and that the
gap between the end of each
electrode and the ground barrier
is spaced per Figure 5.
Check that the Ignitor Air
Defl ector is at the correct angle
(45°). See Figure 4.
Ignitor trouble will be evidenced by failure of main burner ignition. It may also be indicated by poor or
erratic relay response which cannot be remedied by ignitor gas adjustment, or it may cause frequent
Flame Safeguard lockout. Check for dirt in the ignitor air and mixture passageways and check for
obstructions in the ignitor ports. Also check electrode adjustments (see Figure 5). Replace any
severely burned parts.
Proper operation of the fl ame sensor
rod can be checked by measuring the
fl ame signal. With the Flame Safeguard
energized and only the ignitor burning,
a good reading should run steady 2 or
more volts DC.
When servicing, clean the Ignitor
Retention Plate ports and blow out the
internal air and gas passages. Clean
the Electrode Insulators and check
them for hairline cracks. Also check the
electrode ends and the Ground Barrier
for serious corrosion or loss of metal.
Replace any defective parts.
Make sure that there is no debris in
the Blast Tube that could short out the
Spark or Flame Electrode.
Clean the Ignitor Gas Orifi ce in Tee
Orifi ce Fitting (see Figure 5) and check
that the orifi ce size is correct per
Table 4.
VIII Ignitor and
Regulator Assembly
Continued
Ignitor Recommended Ignitor
Type Orifi ce Ignitor Gas Gas
Model of Gas Diameter Pressure Rate
J81A-3 Natural .052 (# 55 Dr.) 6 MBH
Propane .042 (# 58 Dr.) 3.5″ W.C. 7 MBH
J121A-3 Natural .070 (# 50 Dr.) 13 MBH
Propane .063 (# 52 Dr.) 15 MBH
Table 4 - Ignitor Firing Rate
FLAME
SENSOR
SPARK
Figure 4 - General Burner Head Assembly
Figure 5 - Type “3” Ignitor and
Regulator Assembly
