Midco J83-DS - Manual (Page 8)

„ Ignitor trouble will be evi-
denced by failure of main burn-
er ignition. It may cause fre-
quent Electronic Control lock-
out. 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 flame sensor rod can be checked by measuring the flame cur-
rent. With the Electronic Control energized, a good reading should run steady 2 or more
microamps.
„ 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 Orifice in Tee Orifice Fitting (see Figure 5) and check that the ori-
fice size is correct per Table 3.
„ 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 Deflector is at the correct angle (45°). See Figure 4.
„ 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 flame signal failure.
SPARK TEST—Main Manual
Shut-Off Valve must be off.
Place the Ignitor Assembly on
top of the burner with the elec-
trode ends visible and good
metal to metal contact between
the Ignitor Mounting Plate and
the burner chassis.
„ Connect the high voltage wire
to the spark electrode. Spark
should be visible during 6-sec-
ond trial for ignition period and
arc from the electrode end to
the Ground Barrier. It should be
audible and visible, though it is
rather thin and difficult to see in
bright light.
CAUTION: Circuit has
30,000 volt open circuit poten-
tial.
„ If the spark is not audible or
visible it is leaking directly to
ground. Before removing elec-
trodes, check to make sure volt-
age is available by positioning
the spark wire 1/8" from the end
of the electrode.
„ Disconnect Flame Electrode wire and switch the high voltage wire to the flame electrode
and repeat test for insulator leakage.
CAUTION: Do not indiscriminately change the ignitor gas orifice size as ignition
troubles are rarely cured in this manner. The ignitor utilizes a premixed gas/air mixture
and, as the air input is relatively fixed, any adjustment to the gas/air ratio that might
be required for a specific application should be made by careful adjustment of the igni-
tor regulator to vary its outlet gas pressure. Pressure adjustments must be made when
the gas is flowing. If cleaning and electrode adjustment does not eliminate an ignition
problem, further checks are required. Refer to Trouble Chart.
8
Part 1 Service
Table 3: Ignitor Firing Rate
Type of
Gas
NATURAL
PROPANE
6 MBH
7 MBH
Ignitor Orifice
Diameter
.052 (#55Dr.)
.042 (#58Dr.)
Recommended
Ignitor Gas Pressure
Ignitor
Gas Rate
3.5” W.C.
Figure 5: Ignitor and Flame Sensor Assembly
VIII Ignitor &
Regulator
Assembly
Continued